Hot water doesn't drain.

Maine · Nov 27, 2009

I have a problem I can't figure out. My sink doesn't not drain when I'm using the hot water (or it drains very, very slowly), but it drains perfectly when I'm using the cold water. There is no mechanical drain stopper on this model faucet (Grohe Tenso 32425 Deck Mount Vessel Faucet). Anyone have any ideas.

Doherty Plumbing · Nov 27, 2009

maine said:
I have a problem I can't figure out. My sink doesn't not drain when I'm using the hot water (or it drains very, very slowly), but it drains perfectly when I'm using the cold water. There is no mechanical drain stopper on this model faucet (Grohe Tenso 32425 Deck Mount Vessel Faucet). Anyone have any ideas.

Without meaning to sound rude but.... it's impossible the sink will drain cold water but not hot water. How would the sink know what's being dumped into it?

Unless your hot and cold are seperated through the drainage some how?????

Sponsor · 2022-01-29T12:20:58-0800

Maine · Nov 27, 2009

Doherty Plumbing said:
Without meaning to sound rude but.... it's impossible the sink will drain cold water but not hot water. How would the sink know what's being dumped into it?

Unless your hot and cold are seperated through the drainage some how?????

Thanks for the reply. I know. It seems crazy. The only thing I can think of is that perhaps there is something in the drain or a pipe connection that is expanding in the heat of the hot water. I was hoping to find someone who has had a similar situation. I guess you have not.

BurleyMike · Nov 27, 2009

Perhaps something is restricting the flow on the cold side so you have less volume of cold water entering the sink?

How about dumping a pot of cold water in the sink and timing how long it takes to go down. Then use the hot tap to fill the same pot and time it. I bet it is the same.

ChuckS · Nov 27, 2009

I had this same problem some years ago. I gave up drugs and it went away.

Maine · Nov 28, 2009

ChuckS said:
I had this same problem some years ago. I gave up drugs and it went away.

Oh, Chuck... LOL. You're so funny. "Gave up drugs"... you kill me. You should give up trying to be funny.

hj · Nov 28, 2009

drain

Almost ALL vessel sinks have drainage problems because of the lack of an overflow opening to vent trapped air. IF your hot water flows faster than the cold, it will "cover" the drain openings and cause the problem. Next time, take a straw and stick it through the water and down the drain to see if that hastens the drain process. You may have to hold your finger over the end of the straw until you get it into position to keep water out of the straw, which could prevent it from doing its job.

williab · Aug 5, 2010

Hi, I have exactly the same problem. fill the kitchen sink with cold water and it drains perfectly. Fill it with hot water and it gets stuck. I've had a plumber check all the pipes are not blocked. I'm figuring its something to do with an air lock of some sort but I really have no idea - did you ever resove your issue and are you able to help! Cheers

hj · Aug 5, 2010

Hot water is lighter than cold water, but I doubt that it is light enough to "float" in the air and not go down the drain. A good plumber should be able to diagnose it if he sees it happening, but a plane ticket to Birmingham, plus my fees, would be too expensive to do it.

tlarson · Aug 7, 2010

I have exactly the same problem iin a kitchen sink n a 3 year old house that I built on the Washington coast. I did all the plumbing and have measured the hot and cold flow separately and they are exactly the same. The drain rate difference is not too great so we just live with it. I posted about this a year or so ago with similar responses. There is a logical explanation, but I have no idea what it is.

flukmanji · Mar 25, 2013

Urghh! i am having the same problem....and it has only been two days since a complete new sink has been installed in my new bathroom. so definitely the pipes are not Clogged. Has anyone been able to resolve this issue? it is definitely something to do with the trapped air or....Please advise how to solve this issue. any suggestions will be appreciated. thanks.

Jadnashua · Mar 25, 2013

The size of the holes in the grid drain can make a difference...larger holes and it will likely drain better.
Hot water tends to get stripped of any trapped gasses. No idea if this might make a difference.

Mrsheagy6 · Jun 6, 2013

I have this same issue with my new kitchen sink. No one really believes me until they see it . There has to be a reason. I sure would like to know what it is.

crazyquestion · Jan 25, 2017

I have the same issue with a newly installed vessel sink in the basement. Think it was OK until shower was connected . Doesn't make ant sense. Have tried many things to correct it with pressure, clean out etc. but no improvement. Glad to hear I'm not completely crazy. Cold water goes down immediately. Can't even fill the sink but hot water collects and slowly drains. If I fill the sink with hot water from the kettle up past the spot where tap water stops collecting, the added pressure makes the hot water drain quickly. There is only a grid on the drain no stopper. Could there be something hot water is reacting with to close off the vent? Seems to be air block but why?

AlanTech · Nov 3, 2018

I am concerned about the rude remarks. The writers must have been on drugs. Yes this is an actual problem and I had an old plumber fix it after the drain was cleaned and several other plumbers failed to find a problem. I am not on a sewer system but an old septic system. The kitchen drain narrows underground to just a 1 inch pipe entering the grease trap. Somehow hot water forms an equivalent to a vapor lock. The old guy drilled a hole near the top of the grease trap and installed a small vent pipe above ground. Even if you are on a sewer system, ask an old plumber about venting problems.

Kreemoweet · Nov 3, 2018

Heat will cause air to expand, and if there's some sort of air pocket trapped in the drainway, it will exert
increased pressure as it expands. Drains with poor venting (and that includes any drain "vented" only
with an air admittance valve) could be affected.

It's a real shame that some folks are unable to distinguish between rudeness and (attempts at) humor.

seann · Nov 3, 2018

I have been a service plumber for about 20 years and I have encountered vapor locks before, but to be honest I have never ran into a sink that only drains cold water, but not hot. I also thought this thread was a joke also at first. With the other people chiming in with the same problem I guess it's a real issue. If we are honest, we all run into things once in a while as plumbers that we have never seen before and we are always learning. I'd love to hear the remedy for this problem in case I ever run into it at some point in the field. My guess is some sort of vapor lock issue, poor venting, or a blockage in the drain. Is there an air admittance valve or auto vent serving this fixture? I would start by cabling this drain out and see where your at after that. Next, if you have an air admittance vavle, auto vent, or similar I would try unscrewing it or removing it and see if it drains ok after that. In case for some wierd reason it was causing the issue. Or do these in reverse order. After that I honestly don't know what to tell you. It's a puzzling situation having never ran into the issue before and without actually seeing the sink in question. I hope someone has an answer for you as I would love to learn from this myself. Good luck!

Plumber69 · Nov 3, 2018

maine said:
I have a problem I can't figure out. My sink doesn't not drain when I'm using the hot water (or it drains very, very slowly), but it drains perfectly when I'm using the cold water. There is no mechanical drain stopper on this model faucet (Grohe Tenso 32425 Deck Mount Vessel Faucet). Anyone have any ideas.

Drill the holes in the strainer bigger

LePetitPrince · Feb 3, 2019

I found the answer somewhere else. I was having this same issue and it was driving me nuts. Why the hell would it matter if the water was hot or cold? The pipes wouldn’t shrink or expand fast enough for that to make a difference, even if that effect was great enough to cause the problem (which it shouldn’t be).

Turns out, my sink’s drainage holes were too small and we don’t have a vent anywhere. The water tension was forming a membrane under the drain opening. It didn’t matter when the water was cold, but when it was hot, it heated up the air pocket and created an area of high(er) pressure. This pushed back against the water trying to drain and slowed it down.

I poked a short piece of straw through the drain, and now it drains just fine. I’m going to talk to my landlord about a more permanent option - I’m moving out soon, but it’d be good for him to fix it for the next people anyways.

Terry · Feb 3, 2019

Hot water doesn't drain.

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