Why Does My Boiler Keep Losing Pressure?

[@gurglejug627]

Don't be shy/modest about the presentation - it takes loads of skill to present 36 minutes of video with smooth and clear speech and not have to edit it loads - nicely done. Thanks for lots of good info. Sadly it's true what people say in the comments - a lot of people don't know their job anymore and to be able to work out the problem oneself saves loads of time, money and hassle and it make it easier to identify a trader who does know what they are doing. Nice one.

[@simonreeves2017]

Hi Roger, your video series is excellent. I’m nearly 60, I am so grateful that my Dad is a very practical guy and gave me a great education in my youth. This has empowered me so much in life, from maintaining my own cars, installing kitchens and bathrooms, to plumbing and electrical work. Sadly these are skills that subsequent generations seem to have missed out on, the number of times I have helped friends and family where so called professionals have been utterly useless amazes me.

[@eddr]

This has got to be one of the best, most informative, well explained, no nonsense videos I’ve ever watched on KZbin. We’re losing pressure somewhere and this has helped me understand much more than I already did with what could possibly be causing it. Well done sir!

[@mr-jack]

Roger, thanks very much for this video, diagnosis is a tricky thing and sharing your years of experience is of great value. I drained my system just over a year ago and after filling it up again the boiler kept tripping out, the pressure kept falling and flooding out of the pressure relief and I had to keep topping it up. I thought it was probably the expansion vessel but, not being a plumber, I wasn't sure. I contacted a few plumbers but none of them were interested in doing an investigation to find out what was wrong. I turned down the temperature on the boiler, which pretty much fixed the overheating, but I have been topping it up every week or so for the past year and a bit. Thanks to your suggestion of pressing the air valve to see if water came out, I was able to confirm that the diaphragm was gone and immediately ordered a replacement expansion tank. It's all fitted now and hopefully my days of weekly topping up are over. Once again, Thanks very much!!

[@raymondbaddeley6467]

I know hardly anything about heating systems and plumbing ; but I found your presentation to be extremely informative, entertaining and easy to understand. Many thanks!

[@SkillBuilder]

Glad you enjoyed it!

[@rodadamowicz2175]

I just want to offer my thanks to you for helping me find ' a micro- leak ' in my C/H system. After all my efforts failed to find the leak, I followed your advice and added a reasonable amount of ' cheap, smelly perfume ' into the system. Closed all the doors to each room and waited for an hour or so for the perfume to circulate around the system. Entered each room in turn and low and behold, I found the troublesome leak in a room with a strong 'perfume' odour. Can't thank you enough. Very kind regards for your expert advice. Rod.

[@SkillBuilder]

Hi Rod That is great to know, some plumbers ridicule this method but I have used it a number of times and it has always worked. It makes my question why anyone would feel threatened by it but some plumbers are really hostile,

[@jimdavis5230]

Hi Roger, I like your idea of using perfume to find a water leak. About two years ago I had a tiny leak I couldn't find. Boiler pressure would go down just below the normal 1 bar in about a year. I used a stink bomb and injected it into the water system. No problem finding the leak with that terrible smell. Turned out to be a compression joint on a micro bore pipe to a radiator in my kitchen. Seems to me that a nasty smell is easier to find compared to a nice smell. Also a nasty smell gives you more incentive to find the leak quickly.

[@LabRat6619]

Now no leak, but a smell of sulphur lingers.

[@jimdavis5230]

@@LabRat6619 Hydrogen Sulphide smells like rotten eggs, similar to bad farts. Luckily most farts don't smell that bad most of the time. Should you ever release a nasty smelling fart and someone says " have you farted?" You reply saying "of course I have, do you think I always smell like this ?"

[@johnf3326]

@@jimdavis5230 🤣👍

[@Iveraghboy]

@@jimdavis5230 So we could say a fart is a pressure release valve.

[@goffthomas2554]

I find cats piss quite effective too! 😅😅😅😅😅

[@oojimmyflip]

Hi Rodger thanks for all the brilliant videos, I m in a Housing association house and my gas boiler was installed in 2014 which is a Worcester combi ,it has taken 10 so called engineers to diagnose that the heat exchanger is leaking, they now have to supply 2 men to remove the boiler from the wall as they have fitted it to close to the ceiling to remove the heat exchanger and replace it. I used to fit boilers years ago in the 1980s and we used to pay a corgi registered (in those days) chap to come and connect it up and issue a certificate, which is no longer possible, Ive been telling the engineers that its the heat exchanger for years but they are mostly clueless. Id name and shame them but not sure if you allow that sort of thing. fortunately the boiler still runs without pressure but I bet the inhibitor has vapoured away through the chimney as steam years ago. I bet the scale protector has clogged up a lot to. currently if you top it up with the external loop which in a rented property they say is my responsibility, the pressure has dropped again by the next day to 0. The last one diagnosed it fine but he still reffered to the boiler as a valiant boiler, I think they struggle to actually read the name of the boiler on the front panel sometimes.

[@duncanicook]

I think like many other aluminium heat exchangers that have not had enough inhibitor in the system...over time it will damage the heat exchanger. Have come across this 3 times with Worcesters in the last 8-10 years

[@singbob]

Must be a council/housing association thing to employ these kind of engineers, I mean you want your engineers to be competent and skilled when working with certain supplies/appliances, be it gas or electricity.

[@railway-share3820]

Did the engineers work for a firm beginning with D.

[@knockshinnoch1950]

An EXCELLENT practical clearly explained presentation. A presentation like this takes real skill and expertise!

[@tetron62]

What an excellent public speaker this guy is. Direct and clear explanations with nothing superfluous. Very rare.

[@chriscollins508]

Hello Roger. It's really refreshing to listen to someone who knows what they are talking about because they are speaking from experience. A great presentation full of useful and interesting advice. Thank you.

[@oursayso]

Thanks Roger. You’re a star. And funnily enough, if I close my eyes and just listen to you, you sound like Anton de Beke!

[@RexTheJack]

Thanks

[@SkillBuilder]

Thank you

[@adriangoodrich4306]

I learned more about how modern boilers work in this video than everything else I have learned over a lot of years! Always love your videos, but this one was outstanding! SO well explained!

[@linux327]

I had the opposite reason with radiator pressure gradually increasing; when the boiler pump for the hot water had failed and would dump the hot water in the heat exchanger back into the radiator circuit. The expansion tank pressure was correctly set.

[@phoenixgaminglt4749]

Brilliant, well explained and easy to understand. Im a plumber with 7yrs experience but that was spot on. Exactly how they taught it at college

[@mbuk-zm3hc]

Did anyone on your course question why the heck this adjustment of pressure is not automatic? Seems odd to me - why can't the system pressure be measured automatically and adjusted automatically? It seems extraordinary that you have to do his manually. Anyway - going to be academic soon - since we're all going electric air-pump, aren't we?!

[@nigelcartwright5986]

I had my system changed from an open vented to a sealed system about 5 years ago. Never fully understood how it all worked, but I do now. Thank you very much.

[@Mariuszkwiatkowski12]

Robert. This material is so comprehensive that helped to understand the dependencies and have broader overview. Really I appreciate you sharing your experience. I have drop of the pressure from 1.8 to 1.1 bar every abot six monts. The instalation is about 3 years old. Boiler with external 200l water container for hot water. So I'm going to start with checking this air pressure compensation container.

[@sebastiaandevries6428]

in holland we normally have expension vessels outside the boiler and since the pressure of the cold water is higher then the boilerpressure youre last solution is the other way around with us. for looking at the condensing part of the heat exchanger: we often uses hoses to connect the condensing part so we fill the heater up high and let the hose hang in a cold way above a bucket.

[@Traumahawk007]

Brilliant, seen so many alleged heating experts on here that couldn’t explain what you have done in this video.

[@scaryfakevirus]

We had a new Vaillant combi boiler fitted a few years ago which began losing pressure. I couldn't find any leaks at all but eventually had to call an engineer. He came readily armed with a valve so obviously knew the problem beforehand. When I asked why I couldn't find any leaks he said that I wouldn't necessarily notice one because there was a drip tray underneath (very reassuring!) and the heat from the boiler would have evaporated it. Pretty good boiler otherwise but lost pressure yesterday resulting in no heat, so that's why I am watching your video today. Re-pressurised it again and OK at the moment.

[@SkillBuilder]

Yes that is the auto air valve inside the boiler. They can let out a bit of moisture and it evaporates out through the flue.

[@peterthompson6317]

Roger an easy way to check if the coil has gone in a open vented system is to bung your heating expansion tank and then start to run off some water from the heating circuit it will keep running if the coil has split,you will find the domestic tank ball valve starts to drip or run.

[@andypsunshineisle5655]

Very comprehensive covering a lot of ground. I have a system which builds pressure but i am waiting for my annual Gas safe service to change the expansion vessel which has a wet schrader and the same clunk sound all round as the system pressure runs up from setting initially at 1.3 bar to level off at 2bar cold and runs at 2.6 so no major fluid losses so far . My boiler is 11 years in service now so my main fears will be upset valves after they have been resting for so long.

[@paulsimpson1514]

Excellent video Roger... You're a great teacher and explained that in terms that we 'DIY can't afford gas engineers' can now clearly identify where the leak may reside. Thanks.

[@paulsimpson1514]

Yes yes, you recommend that we always use a qualified gas engineer 😅

[@yoya4766]

Most of us diy'ers are probably better than the so called 'qualified' ones. The courses are very bad these days.@@paulsimpson1514

[@chrissmith2114]

Our system boiler is in the garage, there is an integral expansion vessel behind the boiler but the schrader valve is way up on the top of the boiler and hard to get to, so I fitted an 18 litre ( way overkill, but we have 14 radiators in the house ) expansion vessel via a tee in the return leg. The pressure gauge is rock solid whether the boiler is hot or cold... I always keep the system well topped up with inhibitor so no chance of corrosion in the expansion vessel. Sometimes the discharge valves can leak water out even though they are not at their discharge pressure.

[@Danzwain1]

Thanks Roger a long video but worth every minute

[@anthonyminchinton3399]

Why did we get rid of cold water tanks etc? In the event of one's water being cut off you had enough water in the cold water tank to flush the loo if caught short.

[@lksf9820]

Lots of useful tips there, thank you. One thing though and from about 8.20 onwards you talk about pressurising the EV with air, but you don't say how you're measuring it. I believe this should be done with an air pressure gauge on the Schrader valve, but people could get this wrong and try using the system gauge on the boiler.

[@clivelizwood3916]

Roger, learned a lot more to help my DIY plumbing. As ever, very clear description and summary. I think this is well worth some Night School certificate! Thanks .

[@vegsalad]

Hi Roger, I think you just explained why I has a problem in a previous house with a hot water tank with the header always overflowing even though the ball was below water. I changed both ball cocks in the end and it still overflowed. In the end, fiddling with the level the ball valve cut off in highest tank stopped the overflow so left it with that fudge. Luckily the two tanks were close to the same level. You Never mentioned condensate freezing in the external pipe blocking it and causing the boiler to shut down. Apparently, that is very common and my gas-safe engineer says he always gets very busy with those callouts the first time we have a big freeze.

[@peterthompson6317]

Hi roger when I was a heating engineer I kept some schrider valves in my van and a tool to remove then out of the expansion vessel,sometimes they leaked air.I would also if checking the expansion vessel let all the air out and complete fill the vessel with water then press the vessel valve if water came out I knew the diaphragm had gone in the vessel.

[@SkillBuilder]

That is a great tip. Thanks Peter, I am assuming you are retired now or did you find a better way to earn a living?

[@peterthompson6317]

@@SkillBuilder no I am retired now 43 yrs as a British Gas engineer,for my sins.

[@prnfl]

i was able to follow my pressure issue to the overflow pipe and fix it, thanks to YOU

[@alanbayley3255]

One omission that got me out of a leak problem was Fernox leak sealer. Plumbers were warning against it saying it will block the heat exchanger so I rang Worcester Bosch who recommended it on a new system to seal little leaks and it worked extremely well because taking the house to pieces to try and find a leak can be very expensive and disruptive.

[@johnmac4094]

My main consideration with a leak sealer is how does it know what is supposed to get sealed and what is not. I would/will follow Rogers diagnosis method first and likely find the problem, leak sealer will be my last resort.

[@alanbayley3255]

In no way was I suggesting or even saying to make leak sealers the first port of call. When my plumber had scratched his head and deserted me I had to find a solution. If the boiler manufacturer recommends Fernox Leak sealer and you don't understand the science behind it, is that actually a reason to not use it ? So much advice starts with find yourself a good plumber and believe me I have spent time and a lot of money trying to do just that.

[@johnmac4094]

@@alanbayley3255 I guess the main thing is that it’s nipped your leak in the bud and you’ve probably got away with it not clogging your heat exchanger. The use of Fernox is what brought me onto this enquiry to begin with.

[@johnf3326]

And if the pressure keeps going up, its most likely leaky valves in the (permanently connected) filling loop. Happened to me and my son. Son got a free new plate heat exchanger out of it as service contract engineer insisted it was a pinhole in that despite I told him the disconnected loop had a slow drip, which he said wasn't enough to cause the problem, which he eventually replaced the valve and cured the problem!

[@AgtX999]

tie a piece of kitchen towel round each of the radiator legs, check them now & then to see if any of them get damp from a leaky joint.

[@AdamDitheridge]

FYI Our long term 'leak' was due to the expansion vessel gradually losing pressure. We were searching for a physical water leak around the property for months. Pumped it up and has been fine since.

[@0skar9193]

I live in a fairly large 4 bed rented 1970's house with what looks like original rads. The house used to be on an oil fired heating system with immersion heater and a tank in loft etc. In the last 20 years the house was finally connected to mains gas. As part of this the old oil fired heater was removed and old systems decommissioned but old rads left in place. A nice new combi heater was installed, but because this system runs at a higher pressure there was all sorts of leaked and most of the rads had TRV's fitted. This combi heater broke down 3 years after we moved in. A Baxi has been fitted. I'm having to constantly repressurise the system. I haven't found any pipe leaks (I work in property maintenance so I do know a little bit about what to look for). I have reported this to the letting agent and the plumber came and told me that I should report it to Baxi... I'm the tenant it's not my responsibility. I just wish that more "plumbers" watched your vids Roger, they might actually learn something and do a better job. Having watched this vid, when the engineer next comes to do a service I'm going to insist he checks the expansion vessel pressure and the pressure relief valve and for internal boiler leaks.

[@christophergreenwell4912]

One item not covered and may result in pressure loss is failure of the schrader valve. I was advised to replace the boiler because of daily pressure loss requiring re pressure every day. I got a new boiler fitted and when the old one was stripped out it was found that all that was needed was a new Shrader valve. Like a car tyre sometimes you need a new valve. £1200 down the tubes for a new Baxi Platinum was the result!

[@ukhan999]

this guy is awesome, thank you. i just fixed my radiator heating issues, the farthest radiator was not heating up and this trick worked amazingly

[@SkillBuilder]

Glad it helped

[@tinytonymaloney7832]

That was a brilliant lecture. You should teach in a plumbing/heating college. It will see you through till retirement 🤣🤣

[@SkillBuilder]

I used to teach but there is no money in it. I am past retirement age but I am happy working on the tools

[@trevorfitzpatrick5114]

Had a prsure problem would need toping up once or twice a year and told by service guy it was normal till one year, a different engineer noticed the pressure relief valve had been leaking. Replaced it and never had to top it up unless I check radiator bleed valves once a year.

[@deathonawhitehorse]

The flow turbine adapter was leaking on mine for years and I never noticed it. It was a drip every now and then, and until I placed a towel directly underneath and left it overnight did I notice a tiny damp patch, almost imperceptible. I ordered a new adapter, removed the old crusty piece of s**t and replaced it. Now the water pressure is relatively constant and with the expansion pressure back to 1 bar it holds nicely. Those baffles were a real pain in the a$$ to get out being that the flue was directly over it! Mine is a greenstar 28i junior.

[@gordonlofts4674]

Thanks for the knowledge, I found that my system had two 2 port valves with a split heating system operating across 2 zones. I was losing boiler pressure and happened to mention it to a next door as we are on a newish build estate he mentioned that he had to have both replaced. I checked the valves and found a wet carpet in the cupboard which I now plan on changing both of them as might as well if the system is drained looks like to have a weep from inside the valve/motor. Fingers crossed..

[@brettrigby2226]

absolutely loved this video, its so informative. if i was to learn plumbing this is the man i'd want to teach me

[@IAmDanIAmNotSam]

My boiler was losing pressure and leaking out the bottom. put a bucket under it. Limescale cured the problem after a year or so. F'ing love it when neglect fixes the problem

[@sandrar9649]

Hi. Well explained. Had preasure system put in 10 years ago, about to have 4th preasure vessel installed - the rubber diaphragms only last a couple of years - wish we had stuck to old fashioned conventional system as only ever cost regular boiler service.

[@isabellevince5174]

Have a look at the videos which explain why it's not always a damaged diaphram. Condensation can build up in the EV which can be drained down and repressurised. Most engineers just want to replace the EV or add an external one.

[@davidlongman2341]

Our system is plagued with leaks and gradual pressure loss because of water leaking up the operating plungers on thermostatic rad valves. The small operating plungers pass through an O ring, become slightly corroded over time and start to leak through the O ring seal up the piston and out of the head of the valve. Not operating the thermostatic heads does not help because they react to room temperature and move themselves as the seasons change. We get leaks on TRV's that we never move. This is the only repair our system ever needs because it is fairly new but it is a persistant pain in the backside. We are considering going back to a standard servicable on off valve in place of the TRV's when we have them changed in future to save a lot of expense and avoidable botheration. It won't be long before all the rads are sporting a nice new shiny lockshield type turn it on turn it off valve. We have tried the TRV route and found it to be too much of an expensive nuisance to persist with. BUT this is a definate source of leaks on a system fitted with these valves, and they can be sneaky because the leaks start off small and can do damage to skirting flooring and decoration before you catch on to them.

[@daveofyorkshire301]

The expansion tank in the boiler was my issue. After replacement my bills dropped and the pressure in the boiler instead of rising considerably - remained stable. I was topping up the closed system every month or so, and there was a considerable amount of steam during boiler operation - which was the tip I had there was an issue 8n the boiler and nit a leak in the system...

[@tectorama]

Not sure if you mentioned this, but a sudden loss of pressure can be due to the mains filler letting by. These should be disconnected and capped off once the the system has been filled. Although on a lot of boilers the filling loop is built into the boiler. If the boiler goes over pressure (usually over 3 bar) it will blow off to outside..

[@SuperJinxter]

If it’s sudden loss, it won’t be the filling loop passing.

[@jamiefors5062]

Well explained Roger, thank you.....Ive had a new boiler and cylinder fitted about 6 months ago, I now have the problem of the F and E tank filling up and overflowing and yup, you guessed it, plumber seems to have disappeared and not answering any calls or mails

[@Jules_Pew]

Get another plumber who might be able to get the work done under warranty. Happened to me 20 years ago.

[@nickmcphee7004]

Cheers buddy, thanks for the explanation in why my boiler is losing water pressure.. Fantastic 👍 ⭐⭐⭐⭐⭐

[@gordonmcconachie2492]

Your words of wisdom have been a lot of food for thought and most useful thank you.

[@Alfiepops]

I’ve been topping my boiler up every day for the last week with 5 visits in a week from gas a safe engineer who can’t find my leak. The condenser drain had a broken pipe so he left it flowing into a bucket overnight and next day it’s half full . Now the condenser drain has been redirected to a pot in front garden , no heating again tonight or hot water waiting on a overnight pressure test on boiler ? The engineer said ? Hopefully get to the bottom of this by tomorrow.. nightmare to say the least !! After watching your video I think he’s not want to fit a new heat exchanger .

[@dartmoorkid4797]

Actually the diaphragm runs top to bottom as determined by the seam on the vessel but let's not split hairs.

[@keithwilkinson8310]

Thanks for an incredibly useful video. I now realise why, as well as keeping within warrenty, a regular service is important and such as good idea.

[@daves570]

Another idea to detect leaks - how about UV dye as used in car air con systems? Obviously no good for leaks under floor where no access but cheaper than expensive ms gas detection.

[@alanvcraig]

My Ariston combi, now replaced, lost pressure overnight to zero but luckily continued working. Eventually traced to a leaky schrader valve after many years!

[@hmmslagathor9285]

Hi, thank you for this video, during the winter I have to refill my radiators once a week every week. So often my family have a system in place to make it quick. During the summer the boiler packs up about 8 times and a quick refill mends that. I have had British Gas around so many times it’s maddening with thermal cameras etc. I have made a note of all the potential problem areas and I will get a plumber round and we can go through them one by one. It can’t be doing my boiler any good. So thank you for this from the bottom of my heart!!!

[@SkillBuilder]

I use some perfume in the system to detect micro leaks

[@stuartbrown1426]

How do you get perfume in the system though .

[@adrian.parker]

Roger on the Radio... it has a ring to it! Great advice on R2 this week. Guest of the year.

[@SkillBuilder]

Thanks Adrian

[@colincampbell3679]

My Heating System was changed fully by the landlord. it is now 7 years old, But the system has all the parts you stated as being on them! I have the modern combi-boiler with heat exchanger and the red big round expansion tank on the side. The thing I hate is the fact that I can't easily see the water pressure gauge due to it being right down the bottom below the boiler about 1.5 foot off the floor in the cupboard and I am now a young man and trying to bend down to that level is hard to do? I also have a system filtering thing on the wall under the red expansion tank. Plus I will also need a torch as no lighting in there. I noticed over say a month the pressure is dropping such that i have to keep refilling the boiler water level. which is a pain since I have trouble bending down to watch the gauge level. The landlord does send a Gas Safety Engineer out every year to test and check the system. I am bleeding the Radiators on and off sometimes you hear air bubbles running through the rads. I had just now had a bathroom radiators changed to a new one as that was rusted on the bottom right corner. I just hoping that the renewing of that small radiator will fix the many years of loosing water pressure? I always makes me laugh that they say it is a "sealed" system. so why do we still have to top up the water then? Not a sealed system then. the tech should be by now so well designed as to have a fully true enclosed sealed system where the water can't leak out at all and just cools down as used and is reused. I think that the pipes the radiators all that should be Stainless Steel or Aluminium no steel and copper as this would save the rusting of the pipes and radiators solving lots of problems down the years of use! All recyclable so no worries there. I will ask the next Gas Safety Engineer to please check those small areas of the seals you stated in the boiler for leaks or bits under the rubber seals just in case there is some mucking up my pressure and water leaking.

[@onnonijhuis849]

Thats wy in the Netherlands we have a expensionfessel from 18 liters. Water will expand 3%, calculate the amount of water in your system ( 240 - 300 liter everage) you need minimum of 9 liters. At the same time there needs to be air in in, also 9 liters thats wy minimum 18 liters expensionfessel.

[@nickwinn7812]

Very few sealed systems have more than 100L in them.

[@42RHD]

Thank you. Don't know why I didn't see this one earlier when it came out, would have really helped me with my exams. It does explain why my Ariston boiler tried to kill me in 2011 which was when I got interested in plumbing! Leaking heat exchanger. I told Ariston's service engineers there was water dripping very slowly out of the bottom of the combi and it was losing pressure, but they couldn't find anything. The engineer took the face plate off the combustion chamber and lit the boiler. A six foot jet of flame shot out and fried the wiring. He said it was fine. It was a cold February and the boiler was lighting with a huge BANG every time which I now know was forcing gasses out the sides of the faceplate. I phoned Ariston and was assured it was perfectly safe or it wouldn't work. I was falling asleep on the sofa with a massive headache when it suddenly occurred to me to look up Carbon monoxide poisoning symptoms. I was very lucky there. I had weeks of oxygen treatment and the boiler was condemned.

[@42RHD]

@@jamesm4172 Thank you!

[@duncanicook]

Hi Roger, Thanks for another great video. Another way to check the heat exchanger on a boiler is to disconnect the condensate pipe, put bowl underneath, isolate boiler, pressurise to 2.5 bar leave for a while and then check for water in bowl. Personally I'm not keen on leaving "dead" expansion vessels in a boiler without isolation and fitting an external vessel as over time the vessel will start to leak, so needing another visit to either isolate or replace vessel. Very into fitting slave vessels though, alot of the time needed, but also means boiler will not need topping up between services which is great for people, especially Tenants in rented properties. Going onto heat exchanger failures, we are now testing for concentration of inhibitor (if any) at every service.

[@SuperJinxter]

The condensate would be good if it was the main heat-ex but as an experienced engineer, it’s not the first place I would look.

[@yangcao444]

Hi Roger, we have a pressure loss issue really bothers us for two years now and hope you can give some expert comments here. In short, boiler pressure remains the same in summer, but drops in winter when the heating is on. It is a Logic C35 combi boiler for heating and hot water (shower and taps), with no hot water cylinder fitted. Static pressure in the system was at 1.8 bar at end of April (last day we used central heating); pressure was still at 1.8 bar at end of Sep (no central heating used for the whole summer); then we Oct comes, and when we started using central heating again, boiler pressure starts to drop, to 1.3 bar (static) in the last 2 weeks. We are keen to know from your experience, where do you think the problem could be. The local plumber suggests fitting a expansion vessel as we’ve 13 radiators, we are OK with the idea so to take some pressure off the system, and if that solves the problem. For your information, currently, the static pressure is 1.3 bar, it goes up to 1.5 bar when the hot water tap is open, then to 1.9 bar when the central heating is on, and we never let it runs to 3 bar where it triggers the pressure release valve. Your comments is very much appreciated.

[@charlessarner5566]

Problem is likely to be loss of air charge on the expansion vessel.

[@yangcao444]

@@charlessarner5566 Thanks Charles, and would you have recommendation to that? Just to top up the built-in expansion vessel in the boiler, or to fit an additional one to the system? Many thanks!

[@David-bl1bt]

@@yangcao444 check the air pressure in the expansion vessel with a car ture pressure gauge if you can access it easily enough. Check what the charge in the pressure vessel should be (often detailed on a sticker on the vessel), pump up to the correct pressure with a pump. Check whether the pressure relief valve is discharging when the heating is running (tie a plastic bag or balloon around the end of the pipe). If it is, then it is likely that the pressure vessel is insufficiency sized and if so an additional one can be added to your system.

[@remco2777]

I had no clue about all of this, but you've done a great job of explaining all of this!

[@ghaderortakand6027]

Thank you for a thorough explanation. Really useful! You covered so much. The plate heat exchanger can also be perforated, leading to a cross contamination of primary and hot-water fluids. Then, depending on which pressure is lower, either the primary pressure drops (rare) or the system keeps getting topped up (not too uncommon). Keep your excellent videos coming.

[@mb-3faze]

In the olden days (with header tank) the replacement of water in the system was automatic (thanks to gravity). What I don't understand is that it is entirely possible to implement an automatic pressure balance system so that the water pressure in the system is always at the correct pressure. This manual balance system is nuts! -especially in my case where the pressure gauge is on the boiler (which is in a lean-to near the gas supply) but the loop gizmo to balance the pressure is at least 70 steps away, upstairs near the hot water tank.

[@pcno2832]

We had something similar going on in the house in which I grew up. The system was not loosing pressure because it automatically refilled itself, but the relief valve was filling the bucket about every week and the radiators, which had automatic bleeders, were constantly venting a little. The problem was that, since it had a tankless ("combi" in UK terminology) tap water heater, the temperature of the system was set to the top of its range so that there would be enough heat for a decent shower (without that, one would have to turn the shower down to a trickle after a few minutes to keep it warm). With that high temperature, the expansion tank was simply not big enough, so the relief valve was always trickling on and off. A proper fix would probably have been an external tap water heater or storage tank, though a bigger expansion tank would have helped. We just lived with it the way it was.

[@smalltown2223]

Thanks for this info. My question is, if I reduce the temperature of the hot water and central heating on the controls of my boiler, do you get less expansion and therefore the pressure is more stable? My pressure relief discharge pipe does discharge water occasionally. I’m topping the system up about 3-4 times a year, but I do run my water and heating quite hot. Thank you.

[@michaeltb1358]

After I had a new boiler and some new radiators installed I was losing pressure slowly for over a year. Finally I realised that the kitchen radiator was always cold. One of the valves had been left closed and it was almost full of air. After filling that radiator and re-pressurising the system pressure losses quickly stopped. I believe the radiator was acting as an expansion vessel. As water entered and exited the radiator it was absorbing some of the air so water was filling the radiator very slowly. The automatic vent released the air so pressure dropped. Now pressure is completely steady.

[@laurencetitusoates6328]

Really informative video thanks Roger.

[@lazylad8544]

Great video on pressure system. 👍👍. I'm always under pressure and leak quite often too. 😉.

[@X-boomer]

That was a lot more technical than expected. Not a DIY job! It’s great to see this level of non-hand-wavy detail on KZbin.

[@Vialli100.]

Good to see your well Roger, been years since I've seen you.. I used to work at Impact Power Tools and Doves in Redhill.. A great presentation as usual..

[@SkillBuilder]

Hi Ray I remember you well with your long blonde hair. Are you still working?

[@Vialli100.]

@@SkillBuilder Not working, I moved to Northumberland. I am a carer for my mum, so am with her everyday. Although I have my own house 300m away.

[@antoniogalluccio4213]

Can't you just open the heat exchanger like you want to service it and check or drips? Or turn the boiler off, leave the filling loop open and disconnect the condense hose from the trap and check for continuous drip?

[@HA05GER]

It's interesting to see how a boiler works. I had pressure loss but nothing obvious as all the boiler drains go straight into the soil stack as my boiler isnt on a outside wall. Had them out to fix as was dropping quick and now onky drops pressure every couple months which i assume by this video is relatively normal.

[@rocstar2001]

Thanks, I watched all the video, in our case the boiler only loses pressure when the central heating is operating, it doesn't lose pressure for the rest of the year when just supplying hot water. Does that narrow down the potential fault? Previously the pressure release valve went but we don't have the external sign this time.

[@michaeloffiler8185]

In 2020, my plumber used an air gun to top up the pressure in the expansion tank inside my 2012 Worcester Boiler. Some tome later, I noticed low pressure and after topping up, it varied with temperature more than I had seen before. I discussed this with the plumber who suggested that the diaphragm in the expansion tank was probably leaking and i agreed to have it rreplaced. This was done and the problem was solved. However, I decided to examine the old tank before disposing of it. I discovered that the problem was not with the disphragm, but just that the schrader valve was not seating correctly. I guess that when the pressure had been adjusted that some dirt must have got stuck in the valve seat and stopped it closing properly. The lesson from this is that after adjusting the pressure in the expansion tank, make sure that there is no air leak from the valve.

[@SkillBuilder]

Hi Michael Those valve cores are sold in Halfords and take seconds to replace. I have found very few leaking diaphragms, thousands of expansion tanks replaced for the sake of a tiny valve. Thanks for the comment

[@antoniogalluccio4213]

Hi roger, I've been a plumber for a while now and new gas safe engineer. Could you do such an informative video to diagnose dhw and ch not working in a combi. Symptoms, strategy to diagnose?

[@MrInalienable]

Used some cheap aftershave from superdrug(other shops are available) no smells in the house, had a sniff at the PRV pipe, nothing, had a sniff at the condensate drain and bingo there it was. Unfortunately it turned out to be the heat exchanger. I'd had plumbers trying to find the leak and they didn't find it, just took my money replacing parts and pipework that they said could have been the problem. Great idea, cheers Roger.

[@SkillBuilder]

I am so pleased it worked for you. Some plumbers laugh at this idea but they are usually doing what you say, taking a punt at parts replacement.

[@uktoker71]

Tring to get my boiler fixed still. 1st thing was the pump had cracked and it was pouring out water, Plumber came out and replaced that. Now i need to keep topping up the radiators every 1.5 hours or so. Plumber said it may need an expansion vessel, but today i noticed water pouring out of the pressure release valve outside the property. Not had heating or hot water for 2 weeks now. :(

[@heidispawsandfins]

Thank you for explaining this - really helpful 😊

[@willbarbero]

Thanks for a very informative video. While I wait for an engineer to come out (they're hard to find this time of the year) I am trying to do some self diagnosis. Vaillant combi, 1 year old. It's losing 0.5 bar every 24 hours. PRV pipe dry. Expansion vessel just serviced. No visible leaks, no excess of air in the radiators. I have noticed a tiny drip running down the condensate pipe (the service engineer didn't even look at it) from a junction elbow. Could this be a significant clue? I am not qualified to disconnect the condensate pipe so I am going to leave it for an engineer to check. It's either that or a complex search for a leak behind the walls or under the floor...

[@SkillBuilder]

Try this, it has worked for me several times when all else fails kzbin.info/www/bejne/gXnSmKWplLSerq8

[@murrayedington]

I had a heat exchanger leak on a Worcester Bosch after about 5 years. The water came out of the condensate drain, which was the giveaway. I had to pay for an hour of labour otherwise they replaced it for free. That was less than the cost of a service which was due, so I was quids in either way.

[@carrickrichards2457]

We lose pressure every 6-9 months or so. But this time the pressure won't go back up. We open the valves, the water runs in, but it goes straight through the boiler and out to the garden over flow, all while the system pressure remains at zero. The boiler is set to 2.6 bar. The pressure relieve valve seems to have bust and sets off at zero pressure!

[@polderesurf]

Really interesting . Lovely clear explanations . Nice one

[@vistron888]

For checking small drips on the PRV a clear sandwich bag wrapped around with a rubber band is a good way. Especially on a hot day.

[@SkillBuilder]

Good tip

[@David-bl1bt]

A condom does the job too 😉

[@BUD-v9r]

Excellent video! I check and charge the vessel on every service of boilers 4+ years old

[@Lodreus]

Super helpful video! One to keep for those moments to jog the memory. We've been living at our home for 3 months now and I must have topped up the boiler with water 4 times.

[@vinceturner3863]

Thanks, very clear explanations of a complex system.

[@pbysome]

This is a great video Roger, made for me thank you.

[@DuncanEdwards.]

Warmzilla wouldn't beat my quote of £50

[@majormule7671]

Excellent video, thx, but all along I was thinking; ... why not just stick with the basic open expansion tank system - works perfectly and automatically - none of these numerous complex maintenance issues ? Just curious.

[@martindownes1907]

Very useful Roger! Thanks

[@stewstube70]

Interesting article. Strangely my Worcester boiler still works even if the pressure is zero, which it was at the start of this month - why would that be? My system holds pressure pretty well over winter but usually loses it over summer so only need to top it up once a year. I'm just surprised my boiler still works though even if the pressure is low.

[@TONE11111]

pressure valve failing?

[@rogerdutton9930]

I had a system in a previous place, which various "Plumbers" came to sort out the central heating, all had to be paid, not one of them sorted it. In the end a friend of me eldest came and spent a while looking at the system, before diagnosing that it had been plumbed in to run backwards! The overflow tank in the loft was full of hot water! He came back soon after and sorted it. It had been like that for more than 15 years!

[@luckyrobp]

Extremely I teresting. I have an alpha one about a year old, doesn’t hold pressure, I’m wondering if the pressure vessel was ever pressurised. I had another property with 2 veisseman boilers, the plumber was just checking the system when one started poori g out the bottom, the heater matrix had blown, it was 9 years & 10 months old on a 10 year warranty, saved about £3k by being still in warranty😊

[@tectorama]

Another thing not a pressure issue, but if you have a condensing boiler the condense outlet can freeze in cold weather and the boiler will stop working. This is something you can fix yourself. Many issues on a boiler you can fix yourself if you are competent. You don't need to be Gas Safe registered to work on your own boiler, although it is not recommended if you are touching anything related to the gas supply or flue.

[@robertclery4484]

Great info and the diagrams are very easy to under stand. As I have a leak some where now I know where to start.

[@TWOKDOK1]

Excellent exposition Roger. I wonder how many plumbers know all of the possibilities?

[@bosternou96]

Would you use CT1 Miracle Seal to ensure it there is a leak, it gets sealed?

[@MsDenver2]

Hi can I have some advice my housing association uses a contractor to maintain my boiler but they will not set it up so I can use my thermostat and if I don’t switch my boiler off at night the heating comes on at 2 in the morning. I have complained to the contractor and my landlord numerous times and still they won’t put it right.