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 check valves in the sewer drains?
Author: sum (FL)

I was at Home Depot today shopping for some stuff and there was a plumber talking to another couple shopping there. He was advising them on how to do their project and I just happened to be near by and overheard part of the conversation.

He was telling them to install a 2" in line check valve downstream of their shower trap, the reason being the check valve will stop any sewer from backing up to the shower in case the toilet ever clogs the main drain. He stated it is a good idea to put a check valve just upstream of every branch of a Y.

I was thinking about what he said, and it sounded like a good idea. I just replumbed all four bathroom DWV and if I had known about this I might have done it.

However I started to think about it a little more and I am not sure it is really a good idea. Let's say my toilet drain and the shower drain are at the same level. If I have a clog in the line before the shower line ties in, it wouldn't really matter, it will just back up to the toilet. Now if I have a clog after the shower ties in, the water will back up to both the toilet and the shower. If the shower line check valve stops the back up to the shower, then it will back up to the toilet. The back up will probably cause a rapture in the wax ring seal and leak all over the floor, making a mess of the bottom of the vanity and the floor. If there is no shower check valve, then it will back up to the shower, but the dirty water will be contained within the shower area. Plus the check valve may fail after a while and cause the water to drain slower in the shower.

Am I making sense or there is indeed a clear advantage to having a check valve everywhere?



Edited 2 times.

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 Re: check valves in the sewer drains?
Author: dlh (TX)

you made perfect sense and is why none of us suggested ever doing that

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 Re: check valves in the sewer drains?
Author: caja715 (Non-US)

codes in this area are designed exaclty to what you are saying. toilets need to enter in a specific order, cant see a check valve on a shower saving it. My only thought is if this guy is talking about a basement bathroom, and looking at a sewar back-up, but a normaly open backwater valve should catch that.

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 Re: check valves in the sewer drains?
Author: packy (MA)

check valve at the branch of every "Y" ????

so much for wet venting fixtures.
there needs to be a free flow of air throughout the system. when you flush a toilet, there is a positive slug of air in front of the water. that air needs to go somewhere.

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 Re: check valves in the sewer drains?
Author: hj (AZ)

Personally, I do not think there is EVER a "good" place to put a check/backwater valve in a sewer. They are ALL subject to "fouling" and once that happens they SLOW the backflow but do not stop it. In a shower, it would only take a very small accumulation of hair, and the backwater valve has many "protrusions" which would snag it, to prevent it from working. In additon, a check valve effectively PREVENTS the line from being snaked, Since the valve would "grab" the snake and keep it from being extraced, a plumber would NOT snake the line if he KNEW the valve was there. If he did NOT know of the valve's existence and got his snake trapped, YOU could have an expensive bill by the time he was finished.

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 Re: check valves in the sewer drains?
Author: RWP (SD)

It sounds to me that the ignorant "expert" at Home Depot did not know which end was up!
He needs an intensive course on plumbing codes and practices before he advises anyone else.

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Retired after 50 years of plumbing and heating.

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 Re: check valves in the sewer drains?
Author: LemonPlumber (FL)

Sum.if you want to fix a fouled dwv system .use the advised or six onces of plastic explosives as a cleaner alternative.Hope you know you over heard bowel movements as such!!!!!Way full of it.

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