How to Drain and Vent a Bathroom Sink | Ask This Old House

Ask This Old House plumbing and heating expert Richard Trethewey helps add ventilation to a bathroom sink that is unvented.
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Cost: $100
Time: 2 hours
Skill Level: Moderate
Tools:
Water pump pliers [amzn.to/2NTQlf1]
Basin wrench [amzn.to/2A5p0yf]
Adjustable wrench [amzn.to/2NVmdQy]
Shopping List:
New Faucet [amzn.to/2NSSis1]
Plumber’s putty [amzn.to/32AimfO]
Flexible supply tubing [amzn.to/2QiT5Wj]
PVC drain piping [amzn.to/32Dl4kL]
Air emittance valve [amzn.to/2LL8bxV]
PVC primer [amzn.to/2PZfLud]
PVC glue [amzn.to/2NVjR4e]
Steps:
1. An unvented bathroom sink may have a full S-trap, which may siphon and expose the home to sewer gas.
2. Before doing any plumbing work, turn off the water at the main water supply or at local service valves.
3. Remove the old drain piping.
4. If replacing the faucet, remove that as well.
5. Use plumber’s putty to make a watertight seal on the faucet base plate.
6. Install the faucet per the manufacturer’s instructions.
7. Add flexible supply tubing between the faucet and the shut off valves.
8. Dryfit the PVC drain piping. A P-trap should be used. If venting through the roof is not an option, an air emittance valve can be added at the highest possible place in the cabinet below the sink.
9. Use plumber’s putty on the drain connections to the sink.
10. Prime and glue all PVC pieces for the remainder of the drain.
Resources:
Richard installed the Vega Single Control Centerset Bathroom Faucet in Brushed Nickel [amzn.to/31eFPmg], which is manufactured by Pfister Faucets (www.pfisterfaucets.com/).
All other parts for this project, including PVC drain piping and an air admittance valve can be purchased from a home center or plumbing supply store.
About Ask This Old House TV:
Homeowners have a virtual truckload of questions for us on smaller projects, and we're ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers-and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O'Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.
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How to Drain and Vent a Bathroom Sink | Ask This Old House
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[@ectoplasmicentity]

I imagine Richard in another video replacing an old toilet and placing it on the bed to compare to the new one.

[@cn81821]

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[@heathdetweilerRealtor]

😂😂😂

[@jacobpennock4897]

When I saw that I was like...oh OK. Note to self never do that...

[@allentoyokawa9068]

I can imagine him taking a dump in it while on the bed, and using the sheets to wipe

[@ctfplumbing4910]

@@allentoyokawa9068ewww!

[@maxm745]

I don't have a malfunctioning sink or even own my own sink but I watched this whole video lol

[@arcadion448]

1:56 - as a kid I thought the "tornado" was pretty cool and would play fill the sink up just to see it.

[@PopeJackI]

Was just telling my daughter about the whirlpool in the bathtub growing up. Was always my favorite part of the bath.

[@jacksplumbingvideos7147]

@@PopeJackI you had crap plumbing

[@PopeJackI]

@@jacksplumbingvideos7147 I'm sure I did. It was an early 1900's house my family rented that was all lathe and plaster, old wiring, old plumbing. How bad it all was I'll never know as we moved out when I was 13 before I started learning about all this stuff.

[@iamamish]

I used to wonder why I never saw those old bathtub tornadoes anymore. Now I know why!

[@tomdurkins]

@@jacksplumbingvideos7147 Actually this video proves a vent isn’t always necessary

[@bjornjoseph]

I've learned so much from this show. For example when dry fitting your pvc, use a sharpee to make marks where the orientation of the pipes go dlfor when you glue

[@killja420style]

Use a pencil. At the end, it looks tacky when u have all the nice white pipe up, and sharpie markes all over the place.

[@jackburton1467]

@3:51 "My dead grandmother made this quilt with her bare hands specifically for displaying dirty, old plumbing. Thanks Richard."

[@KingLo]

I didn't know that mini vent was a thing. I had a vanity I wanted to install but couldn't figure out how to pipe it to the vent. Thumbs up for that alone.

[@Thomas-we4du]

As soon as i saw the old plumbing parts on a clean bed sheet i scrolled to the comment section..lo and behold....

[@maximusmax4557]

"Lo and behold."

[@jamesz3846]

You know Rich means business when he puts on his half-glasses.

[@nholt]

lol

[@aaronbaraiya3692]

lol

[@williamtpenningtonart]

Thank you. This helped. About to replace an old vanity and it's plumbed through the floor straight with no trap or vent.

[@michaelrobinson4677]

Very informative, as always. You make it so doable!!

[@BillyN31]

Cleanest pvc I’ve seen under a sink outside new construction. Lol

[@calebwilliams2709]

This is the video I was looking for super helpful. Needed to see that venting solution vs. teeing into the toilet vent going to the roof. Thanks!

[@asafindy]

The wife was NOT mad about the old pipes places on the bedspreads. She considered it a step up from the week before, when the hubby invited his mechanic friend over to replace their car engine. And an even bigger step up from the week before that, when he invited his gardener pal over to replace 20% of their yard soil with manure.

[@samwhite9894]

😂

[@haroldped]

Note this was his girlfriend, not wife. It is only after they get married that old plumbing parts are placed on white family heirloom comforters.

[@danbasta3677]

I love watching This Old House tv programs.

[@eco_guardian]

I love it: he said neither trap would end up having water in them and BOTH OF THEM DID!!!

[@stephensnell1379]

That's because Richard only just drained the water to show the effect of sinks when they don't access to air to drain properly so don't be so dumb,also as he mentions S trap is completely illegal

[@donnaclayton8644]

Thank you! This solves my septic issues!!

[@manofweed1]

Almost 100 % explanation. A perfect job by him, though let down by the pop up. They never 'pop up' far enough to really flush the basin clear quickly.

[@RubbinRobbin]

Tretheway seems very knowledgeable, very under-rated personality in TOH. If TOH can do a proposed HVAC install for a ducted house, that would be the best episode ever.

[@HunterAmes3]

It bothered me that he set the old stuff on the bed

[@AlfredoPesina84]

Hunter Ames maybe Richard told the guy to put a used cloth down so he can explain like he did.

[@OffroadCpl]

Who cares it's a show

[@toast4899]

mays9185 but it's the person's real house. It could make a mess

[@gregsplace.greecenewyork2744]

Dpot knobs are way more dirtier

[@korndawggy1801]

@@toast4899 but did it kill you?

[@yuvgotubekidding]

Wow! Plumbing is really easy!

[@cn81821]

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[@homesteadingkosher1005]

Thanks for a great visual illustration of how we can now re-do every sink in the house lol. Just wondering, what about double sinks? Is there perhaps a video for a vented double sink as well?

[@Streetracerex1998]

Richard loves his putty

[@cliveharrison-43]

DVL AV he used the rest up his jacksy

[@ethelryan257]

I go through a lot of the stuff, too. It's very cheap insurance against otherwise impossible to seal leaks and slow drips which can do real damage over time.

[@Overfl00d]

@@ethelryan257 I heard high grade silicone was better

[@alchance662]

My sink drains thru wall, which is quite common. Will this work as long as the Vent is above the drain pipe? Is there a minimal "water drop distance" to drain required for these Vents to work?

[@jordanplant4229]

Thank you! That was the info I needed!

[@rosewd2]

Its amazing how some of these modular homes get away WO venting the sinks. We had to use that autovent on 2 bathroom sinks and the kitchen sink to fix them up. Seems like the skip the inspection phase on these.

[@y.5107]

My grandpa was a plumper, I wish he would still be around.... could have learned so much from him

[@meb3153]

This is gold

[@japan-e9j]

Excellent job

[@richardcano3134]

Aprendo bastante en estos videos lastima que no puedo ingles. Pero hay vamos algo le entiendo...

[@Scrapper_142]

That airflow demonstration 😂

[@gaberondon8757]

Let’s just put this stuff on your clean bed for now.........

[@GlitchedPepsi]

Stop crying

[@hydrobuu]

Might as well taken crap in his bed.

[@riprockeygaming3041]

Exactly what I was thinking lmao

[@gobucs3146]

Lol, exactly what I came to comment

[@brewster102]

That's not the first time pipe was laid on that bed

[@davidredpath4781]

Great video!

[@garyjerniganjr]

I had an issue with the vent (let the sewer smell in) and replaced. Even the new (2) ones failed. Could there be another issue causing this?

[@gaetanobalzo8212]

drained well, good enuff venting

[@stephensnell1379]

It's spelt enough

[@savelikeaprowithleah5157]

Looks Beautiful! Thanks for sharing!

[@fdlb99]

Awesome good job

[@sb8329]

good job 👍

[@kyvvuu]

Amazing

[@brianschnurr3254]

Awesome!

[@jasonpham80]

mine is p trap with air to attic ,but it keep making noise even when not use. is something with the air vent? it annoying at night, can this be fix?

[@phatpunxs64]

Can you use these on kitchen islands that have a sink? Seems like it would be easier to plumb the island than try to hide the vent.

[@tomthumb5106]

Just out of curiosity, you said there would be no water in the traps, yet you poured water from both traps when you changed them. And with the tornado from the top sink was because it was unvented? My tub does the same thing and its vented. I'm just trying to learn. Thank you for your time.

[@ihgoo9926]

so I used red primer in my basement to the stack, do the color matter?

[@whith5184]

what would you do about the poor water pressure? the sink filled so slowly after the new fixture went in. what happened?

[@sapreaper]

Good video on TOH again, but what dip left those H and C water feed lines not fastened? and why cut a big hole in the bottom? I just ripped all mine out iin a finished plaster/lathe house and ran up in the wall. Also, the pop-up stem, at least by Pfister (today) says use NO Putty or sealants. Mine works great, no leaks. The faucet has its own soft gasket too. No putty. Days of putty are hopefully going away :)

[@Engineer9736]

I don’t know if i could live with such faucet. A normal tap puts a lot more force in the water stream. For cleaning your toothbrush after use and so.

[@millsarts]

That's very true. They also cost a lot more

[@HunterAmes3]

I have those in my house and they have plenty of force, but they splash everywhere

[@patrickwhitehead7584]

I thought I wanted them until I stayed in a hotel that had one. They look great and are awesome in a bath tub, but the sink is a NO F'ING WAY!!! Like hunter said- they splash everywhere.

[@Blox117]

not just low pressure but the flow rate looks anemic as well

[@redwings19798]

I didn't like the pressure/flow rate either, but the thing I most disliked was the push button stopper. You have to stick your hand in dirty water to drain the sink. Stupid design in my opinion.

[@Draugluin999]

that is an awesome spout need me one now

[@BiggMo]

Looks like a composite sink, if it is, that putty will cause discoloration around that faucet and drain. Also, many plumbing codes do not allow cheater valves.

[@seanh3563]

Non staining putty exists

[@lucashicks3668]

Thanks for the vid(s)! Question: I've added an in-line vent in the kitchen, but the sink is still gurgling (less than before, but still noticeable). Any ideas why this would be?

[@guidedbygreen1480]

Is the vent after the trap? Reconsider and reevaluate your plumbing. Do you have at least one actual vent on your roof? Maybe you have a blockage

[@asseater1895]

It’s probably the falangy

[@Snarkbar]

Home owner doing his own work? Nicely done! :)

[@AS-xc2xf]

Can I used this for toilet also the vent

[@exceleratorjoshua]

How is this 2 traps? There's 4 of them!!! The other 2 are simply empty and don't hold water. This was a very DIY project with someone who did what they could to save money. I'm glad it was fixed in the end.

[@timwhite3158]

Putting new faucet in . i try to put supply lines on first. Then feed drop in place

[@jebprendergast101]

My plumber just gave me this tip the other day!

[@vishals50]

Wow Wow !!

[@littlehuey5679]

Most codes require that a struder vent be above the overflow on the sink but this one is even with the drain ?

[@krynski1]

Please correct me if I'm wrong but, according to the explanation the plumber gave earlier shouldn't the traps have been empty when he dismantled them?

No, he said a setup like this "could" cause no water in the traps

[@Asteroid_Jam]

Bigger thing he said was the set up was not legal as it was not up to code.

[@iLikeC00kieDough]

It usually won’t completely empty the trap. Just pull out enough water to break the seal

[@abdermnbadrahmed4094]

Good

[@TheSlipperyNoodle]

Little messier than I would expect from a Master Plumber with Richard's experience.

[@abdulelkhatib2674]

Messey? Thats the cleanest pvc I've seen

[@sheepysheeperson2396]

I have some plants that have moved away a bit away from the garden bed can you help me

[@russmarriott2711]

that initial image - the S Trap violation... compounded by the double violation of being a Double S Trap! at that! - glad someone was brought in to fix it!

[@integr8er66]

While this doesn't meet code, I have no idea why people like you get all balled up about these things. Shit still went downhill, the sink still was empty, AND the traps were still full, so its not really that big of a deal

[@Billy28376]

integr8er66 exactly my thoughts as well

[@SuperSurr73]

Brilliant

[@RADMANLIFE]

Studor vents are illegal in most places and used mainly in trailer homes. They often release positive gas pressure ie. Sewer gas into the home.

[@elncalls]

My wife would kill me if I put used old plumbing parts on our clean bedspread. That guy is sleeping on the couch with that dirty blanket now.

[@Mixwell1983]

ELN calls guess you missed the part where he said new faucet.

[@matthew02006]

they had the old and the new on the bed

[@Mixwell1983]

matthew02006 i was watching the faucet part in the box..i see now. Yah def wouldnt put the old pipes on a bed without something underneath.

[@Kalikovision7]

I thought the same thing

[@Nova93Perez]

That's probably a guest room. I'm sure they wash the bedding before someone sleeps on it anyway. The bedding gathers dust even when it's not in use.

[@danedu4519]

I went to buy a transparent trap, no matter what I did I couldnt empty the trap with this case escenario, yes some air will go thru and maybe a small amount of gases will escape for 1 second when the water is going down, but the trap always ended with enough water to prevent gases, while I understand is because of plumbing codes and there is a chance of happening I remember too that blinds with cords are illegal now because somebody killed it self with them!!!

[@bruzote]

Where are these blinds illegal?

[@cliffa8057]

Perfect🤛

[@ShakespeareCafe]

Richard needs to get a DeWalt folding table for $99 from the Home CENTER Depot...(often on sale for $69). You put all your tools on it, so they are not spread out all over the floor and then you can use it to display the old and new plumbing fixtures without putting it on the bed. There's nothing worse than having to bend over to pick up your tools every time you need one. Get organized and your customers will see that.

[@Eashlynne]

Revamping a 1982 Florida house. My landlord is smitten with my ability to diagnose a problem and solving it saving him thousands. It's really not hard with a little experience, Google and youtube at the tip of yo fingers! I already discovered the master plumbling and laundry are interconnected to the vent stack when flushing the sandpipe. Yet the problem bathroom is on the complete opposite sides of the house. My guess that bathroom is tied into the kitchen plumbing as well. I do not believe it's vented and causing the slow drainage in that one bathroom. This house has definitely made me bite off more than I can chew... but how else do you obtain knowledge? Thank for the informative video! I knew these existed but now confident this may solve the problem, now off to lowes I go!

[@ellmatic]

I assume the putty is a sealant so that water doesn't get under the faucet and rot/mold over time. But, how would one properly remove the excess after installation? We didn't get to see that part.

[@andyparks6120]

it just goops out and you grab it with your fingers.

[@tom3fitzgerald]

Awesome

[@Diehard65]

Granted you don't want to get into a lot of detail about the lack of the vent but I would think mention of its primary reason(to protect the trap from losing its seal) would be in order.

[@stephensnell1379]

You would be correct there

[@SlickArmor]

Well he claimed that both traps would be sucked dry but then upon disassembly they both were full. We won't get into laying the nasty thing on the bed.

[@ryanh3951]

They make clear primer for a reason.

[@Intercoaster]

I didn't see an overflow for that sink. Was there one? Apart from on to the floor, that is! And I agree that those waterfall faucets are all about aesthetics and not much function especially as someone else said that sometimes you need a really forceful gush of water. A more common name for mechanical vent is air-admittance valve (AAV).

[@killja420style]

Usually lavatory sinks will have a built-in overflow . When the water overflows, the water will go into the overflow hole & inside of the sink, and then into the pop-up piece/tailpiece.

[@Intercoaster]

@@killja420style I re-watched the video and for a second or two, near the beginning, there's an oblique shot of the sink where the overflow hole is just visible opposite the faucet location as is usual. Easily missed hence my wondering where it was.

[@poptya]

I also like the teflon tape on the compression supply lines lol

[@abdulelkhatib2674]

Teflon is some times used as a type of lubricant on compression fittings to make it easier to tighten

[@PtrOBrn]

does the mechanical vent only have to be above the trap. I have a vessel sink that doesn't drain for hours. The fix I had found online was to hookup a dishwasher line to the pipe and run a hose up into the wall above the height of the sink.

[@bruzote]

Peter, your hose dishwasher hose solution is equivalent to the pop-up drain. The AAV addresses a different venting problem. Youl would still need to either have your hose or get rid of the drain with tiny holes.

[@fantamas06]

I need a PRO into my condo! to replace all of the old plumbing parts.

[@rogerdevero8726]

Richard, (Liked & Subscribed) you have a 'Teacher's Spirit'. Well produced and filmed- Thank You. Romans 10:9-10

[@jawedkhangolden6584]

Sir, myself Jawed Khan from India I want plumbing training with you I impressed your learning and working method

[@cdyoung976]

I know modern code says every drain has to be vented but I couldn't help but notice that both traps were full of water when he disconnected them. The tornado at the drain is allowing air into the pipe. I had a 120 year old house were all the drains were like that. Personally I wouldn't worry too much about an existing drain set up without a vent if there isn't a sewer gas smell or other draining problem. Every houses system is different though.

[@chrisbeggs3945]

This is trash. All you have to do is look at the mess on the pvc that her out back together. You can see the joint slipping in the video

[@ASUSproz]

Are drain vent required? I'm in Canada, bc

[@tomcartwright4375]

Got a problem with my drain just got this house in January. No vent anywhere in the house. Do you have a video showing how to do this. I watch your show all the time. On fix income. Thanks for your show

[@edwardmarshall2035]

Do you have stacks going through your roof?

[@justtruth8310]

Inspectors in MA will not allow me to use Mech vents. And alsow hen I use them not pulling a permit, I run the mech vent all the way up to the bottom of the sink as high as possible. This one is installed lower.

[@mresmith4302]

I still don't know why people come on here just to complain; this is why depression in the U.S. is so dam high. People are simply looking for reasons to be negative. If you know how to drain and vent a bathroom sink then don't watch the dam video. If someone made a video on boiling water there is no way I would watch just to complain about the size of the pot they are using, or the type of stove they have, or the type of faucet they have, or if they have on shoes or not. Try watching something that makes you happy, smile, and breeds positiveness.

[@harrybullard1705]

Thank you!!!

[@michaelcastillo3231]

*damn

[@bluecollar58]

What he said

[@integr8er66]

The reason is spreading false information is damaging to those trying to learn. Some of use care to teach the next generation properly.

[@ScienceBitch123]

But you came on here to complain about peoples complaints 🤔

[@denniscorson8997]

A A V made life so much fun...

[@MS-le1ye]

I had a problem in my house, when I renovated the house, bathroom and toilet, the pluming system didn't have ventilation what happened was a disaster. So the first tiles of the walls were are pushed inward and some of them got broken. Although I put silicon glue under the toilet, the glue became brown and dirty very soon. that was a disaster.

[@KnuckleBallz]

Wife: Honey, why does our bed smells like sewage?

[@jasonbourne3255]

Husband: Did you forget to shower, dear? 😜

[@friggerx3150]

Ahahah

[@egolono10]

Ugh, close your legs, dear

[@stevehairston9940]

Wife : what did I tell you about farting under the covers? 😁

[@oreokookie1000]

because i'm ed norton.

[@user-op8bl5xz8g]

Hello !! I 'am french, i like your channel, but i don' t understand english... 🤔 But your quality work help me and i go understand (sorry translation my mind😂) Thank you very very very much, the France it's a little country, so it's very hard find good channel plumbing ( i am hotman gas, fuel, speciality, i havn't got a good level in plumbing.

[@quintonmorris11]

Your English is good!

[@DOODOOMAN118]

My bathroom sink takes almost a day to drain completely. I removed the pipes but its not plugged so I don’t know what to do.

[@JorgePerez-vi7op]

That's a W trap😄

[@bkilpatr100]

Is plumber's putty ok to use on plastic sink parts? I just did the same thing with my bathroom sink last weekend. The instructions called for silicone on the faucet parts, but I opted to use putty instead. Then I found out it could be bad for the plastic?

[@JoeMNPT]

I just installed a new vanity and faucet last weekend and used silicone because of this very concern.

[@stratorunner1]

Personally i have nothing agains the siclone effects. The first installation works suprisingly good , because the pipe increase in size in the vertical side. Btw ? This is the first time i saw two S-trap intalled for a single unit. Wha ahah ! :)

[@stratorunner1]

​@Doge Hardon Sorry ''c''yclone it produce like a vacuum sound.

[@andysierra5657]

Why was there water in the ptrap where he said there wouldn’t be none.?

[@danielmartinez-zn3jx]

Is that thin wall pvc?

[@panchito1993eljc]

Richie is the goat

[@JTech625]

What kind of person roughs in the supply and drain lines a foot from the wall.

[@erictold]

Bonding P-trap without clean out plug will become a nightmare for homeowner. Why don’t you use either slip connection or install clean out?

[@cescobar5258]

Exactly my point all those wannabe plumbers never ever install a clean out.

[@chefjamesmacinnis]

So you didn't notice that the actual trap is threaded on?

[@basthan1]

So in this video we start with an interior view of the bathroom. Look at the door, absolutely "custom" along with the carpet work. Richard then goes onto tell us that a double trap system won't hold any water then in the next scene we see him empty both traps that are completely full of water into a kitchen pot. A little later we see Richard lay out the old and new plumbing on the bedspread. My wife would be LIVID lol

[@stephensnell1379]

That's because Richard showed what happens to a Sink that's not vented From this Video an unvented Sink sounds TERRIBLE

[@vincentlee2460]

Why is the mechanical vent placed lower than the basin?

[@bradenwelch1967]

I thought he said that both traps wouldn't have water and yet when he took them apart, both traps had water lol

[@stephensnell1379]

That's because he filled up the Sink to show what an sink without a vent will sound like before he got rid of the illegal S trap and then as you saw in the video he replaced it with a P trap

[@EyeintheSky999]

Is there a rule for how high above the drain the vent part has to be?

[@truth6600]

That trap was too high the tailpipe off the sink is always full,not good.

[@ncooty]

Code requires an AAV or vent tie-in to be at least 6 inches above the overflow level of the highest serviced fixture. Everything below that point is considered part of the drain/ waste system, because water/ effluent can back-up into it. I'm pretty sure the way Rich installed that AAV was illegal. EDIT: Code adoption differs by state, so maybe that's legal where that guy lives. The same risk/ rationale applies, though, and it's unfortunate that TOH doesn't mention such things.