Central Heating System Losing Pressure Or Leaking? - Fernox Leak Sealer F4 Express Via Radiator

Our boiler has been losing pressure while the heating system is on, we can't find the leak from any pipes or radiators however the central heating system pressure gauge is dropping over time when the heating is on which suggests a small leak. So we're going to try a product made by Fernox called Central Heating Leak Sealer F4 Express and can be applied via the filling loop or directly into the top of a radiator as we have done in this video. We hope our video is useful and solves your problem, fixing the leak will save water and make the heating system more efficient, not only that it should also extend the life of the boiler as well. You will need some basic tools (adjustable spanner/vise grips) , including a radiator valve bleed key, a container for the water and old towels in case of spillage.
The leak sealer is available from most DIY stores, but here's a link to it:
amzn.to/3N2nsuD
#fernox #centralheating

[@simonw7284]

My advice applies to a combi-boiler/closed system. This is my experience! I think I would only recommend this (as in my case), if you know the leak is not your boiler which is easy to diagnose by isolating the central heating from the boiler. These are normally two red valves under your boiler. Using a screwdriver you turn off both the valves. The pipes are normally larger at 22mm in width). Turn these both off and wait 24 hours (without using the central heating! Turn the timer off (in my case I had on, off, timer, and boost. I used OFF) so no central heating is possible even if someone turns up the thermostat. You could also turn off the boiler completely but you won't have any hot water. If your pressure still drops after isolating the central heating after your period of time you have a leak in the boiler somehow. Quite simply water is escaping from the boiler when it is running. It will be leaking either from 1) the boiler (drips on the floor or the running down the wall where the boiler is) which indicates an internal leak, or a crack in the heat exchanger 2) A leak from the condensation pipe which will normally give off water during normal use. If it is dripping water when the boiler is cold you still have a problem 3) pressure release valve which is not normal to release any water unless the pressure in the central heating exceeds dangerous limits. The system will also lose pressure much more quickly if the expansion tank cannot expand. This "tank" is inside the boiler and helps to take the pressure as the central heating heats up. With heat the pressure will increase, thus this tank expands to take the increase in pressure. This tank should already be pressurised in order to take further expansion. If flat it cannot expand. Its like sucking on a flat balloon. Funnily enough, to expand this tank requires a bicycle pump! So if you think your boiler is leaking I would recommend getting someone in to investigate and not using a leak sealant unless temporary. If after determining your boiler is fine... It must be the central heating. It cant be anything else right? It cannot be if you have isolated the boiler. Its in the pipes feeding your radiators, or the radiators themselves. Check your radiators under each valve while cold or hot (both ends of a radiator). Put some kitchen towel wrapped under each valve (use some masking or other paper tape to make it easier to detect water). It doesn't take long to drop 1-bar of pressure in 24 hours with a slow drip. On hot the water may evaporate, but with some kitchen towel you may detect some evidence. Its obviously easier to detect leaks from upstairs then on the ground floor. I would say that some leaks may only occur when the central heating is either hot (expanded) or cold (contracted) so its worth checking both If after all this.. the leak is not obvious (i.e. on the ceilings or walls from upstairs) then its on the ground floor. If your pipes are buried in concrete on the ground floor (like my house) I have a slow leak. In which case use leak sealant to get you through a year. It will only work with a junction leak, or pinprick leak. To detect a leak will require specialist people whom use both heat detectors and also listening devices (which are much more accurate).

[@EV-pm5gj]

Hi Simon.is it possible that it is the boiler issue of leaking rather the pipes or radiators because on one occasion we re pressurised the boiler at 9am and the pressure stayed on 1.3 from time of re pressurising from 9am to 5pm and only loss pressure when heating is turn on for 2 hours the pressurised dropped to 0.7 then heating off overnight , the pressure stayed same at 0.7 and when heating turn on at 6am the pressure dropped to 0.5 after a couple of hours

[@calvinlee1989]

In the boiler, why would you put it into the pipe where the water comes from rather than the pipe next to it where it goes to?

[@Cmwgas]

Wont work on a pinholed heat ex

[@rikm555]

If your boiler is losing pressure and you can't find a leak it could be that your expansion tank needs repressurizing. You can lose water through the pressure relief valve if the tank pressure is too low.

[@DanielJohnHowTo]

thanks, out install is rather basic but that sounds like something to definitely check.

[@rikm555]

@@DanielJohnHowTo If you have a Combi Boiler the expansion tank is inside it.

[@rikm555]

@Paul-mg7bh You need to close both valves initially. Then drain some water, which will come from inside the radiator and not the pipework. Then tighten it back up. Then add the leak sealer and close the bleed valve. Then open both radiator valves to their previous position. Then check and increase the system pressure. Then turn on the heating an the sealer will travel around the whole system.

[@rikm555]

@Paul-mg7bh One other thing, you will have introduced air into the system so you will need to bleed it after it has been running for a while to get out any air trapped in this radiator, and I would check the rest as well.

[@arz7413]

The F2 same size can instructions doesn't say let anything out of the rad ,? Strangely

[@علیاکبرزارعی-ز4ض]

❤❤❤❤❤

[@salam238]

Its okay for very tiny leaks but not for big ones.

[@EV-pm5gj]

Could someone answer my question pls. Is it normal for the heating on the boiler to be isolated and turn off for 2 days and use the hot water as usual to diagnose if the boiler pressure loss is due to leak on the pipes or problem with the boiler itself. The Engineer came riday have done that and will see the results on Monday. I thought the heating system and hot water is totally separate.so the pressure will not drop in just using hot water bacise the heating is isolated. Pls help me

[@yassarismail8570]

Hi, I have the same issue and Baxi have done the same yesterday. I need to call Engineer tomorrow but at the moment the pressure has not fallen so seems like I have a leak. Like yours he has turned the central heating off

[@ashapatel7358]

@@yassarismail8570 me too!!! I have to keep topping up pressure until Monday. The plumber is going to try the sealant thing and hope it works

[@Smithy225]

Kier starmer has let himself go