My wife and I recently moved into a mobile home and are loving it... most everything is working fine, but I've noticed that the kitchen sink drains very slowly, and tends to get some back-up when the dishwasher is running. 

My first guess was the catch, so I took that off and looked, but it was totally clean... then I unscrewed the air filter thingy just past the catch in the drain pipes, and tried running water... it drained very quickly with no problems. When I went to a store and bought a new air vent and installed it, the sink went back to draining slowly.  

Am I missing something? Something else I should check? Or is that just the way things are gonna be for us? Any suggestions are welcome! Thanks!

When you say catch, are you talking about the pee trap? You could have a plug or restriction somewhere beyond that. You may have to get a rooter and clean the line out from just past the pee trap to the main. Someone with more plumbing experience may have a better idea.

believe you are talking about a vacuum breaker (that gizmo) .. it's not a vent...

it does sound like you have venting issues..

snake the vent line...

When you took the air admittance valve off and you ran water did air pressure come out of it.  If so you have a partial blockage past the P trap.   Probably does not have a true vent at all that is the reason for the air admittance valve.    Roly

Edited September 30, 20169 yr by Roly

I'm with Chips on this...blocked past the trap to the main line.  Not much angle so crud builds up...cooking oils and grease builds up as it cools.  

 

Take trap off and clean the pipe going into the wall...

Edited September 30, 20169 yr by Nickp

My kitchen sink drains into the vertical vent stack and about every 10 years I have to cut the drain and clean the build up when the tee is in the stack.

if the drain has grease build up very hot water poured down the drain may help..

then again it may dislodge clumps that clog things up even more and make the problem worse..

Edited October 1, 20169 yr by Stick486

Removing the vacuum breaker one time and getting flow is not a definitive indicator. If you had done it several times and got the same results, then I would say that the vent stack system was at fault.

 

Are you draining into a septic system or are you on a city service? I agree that there is probably a partial clog in the piping system. If you are on a septic system then tree and shrubbery roots, or grease build-up are usually the culprits. If the vent stack is OK then look to cleaning out the lines. Root infiltration is generally the problem followed by a line collapse.

 

 

If this is the only drain having problems, beside the partial clog is double trapping.   See if the drain pipe from the sink has another trap or large belly in the pipe (acts as a trap ) before the main drain.   Roly

Somewhat off topic, while our kitchen was being replaced due to flooding a couple years ago, our granite counter top fabricator laid out the holes for the faucet and soap dispenser, and asked him what about the "air gap" for the dish washer, he stated no one used them anymore, I asked the plumber on the job, and he stated the same thing, "air gaps are hardly used anymore, plus they make a mess of things when clogs happen, water spills out everywhere and often time over the counter top and it's a big mess". We went with the recommendation, and have not had any issues in the last 2.5 years by not having an air gap. Plus our beautiful counter top looks less crowded too without it.

Just food for thought. Right or wrong, we have not noticed anything bad without the air gap. We have a double sink, disposal, and two year old dishwasher.

 

EDIT: By the way, plumber stated Air Gap installation not needed with newer dishwashers as the waste drains directly into the garbage disposal. Kitchen was inspected upon completion, and inspector had no issue with it.

The vent needs to be plumbed in one of these two ways.  It cannot be plumbed of the side of a horizontal pipe as the water may fill the pipe restricting air flow possibly causing the vent not to open properly.

 

 

Dan, what kind of vent is that shown in your pics?

John, what is an air-gap?

Cal

16 minutes ago, clhyer said:

John, what is an air-gap?

It's that short stack looking thing for the dishwasher that sticks out of your counter top. And sprays all over when you get a clog in your dishwasher drain line.

2 hours ago, clhyer said:

Dan, what kind of vent is that shown in your pics?

John, what is an air-gap?

Cal

The blue one is a Studor but these are images I found to depict the proper installation.

Welcome aboard Past. Hopefully these fine folks can help get your issue resolved