My kitchen sink has a slow drain. So much so that the dishwasher backs up into the sink basin.

I have narrowed the problem down to a vent problem. The pipe the enters the floor doesn't appear to have a vent. I know the drain is not clogged because I can insert a garden hose into the stub and it will never back up. At least not for 10 to 15 minutes. Also, I have installed a tee after the trap figuring the dishwasher would not back up into the sink if it is the last inline. If I hook the dishwasher drain up, fill the sink and drain it it is slow. Once I remove the dishwasher drain the drain runs fast.

I have also tried a inline vent. This didn't work. While draining if I have the vent installed the drain is slow. As soon as the vent is removed the drain is fast.

Before calling a plumber or tearing up the kichen to install a vent to the roof I would like to know if there is another way to solve this problem?

if allowed by your local code, one of these will work.
[www.mobilehomerepair.com]
the actual name is a studor vent
[www.studor.com]

Oh my God...I never would of thought Packy would........not a Pro-vent...

Yes, unplug the main line that the sink is connected to. Your problem is caused by a poor vent, which an inline vent does not cure, and causes your symptoms.

Doesn't matter, it still won't drain. In fact when he refers to an "inline vent" I will bet that he is referring to an AAV.

Yes an inline vent will not work with a forced main, aka your dishwasher. Is there an air gap installed on your dishwasher?

It will until something happens in the downstream side of the line, such as an obstruction which makes the line fill with liquid, and creates a positive pressure air bubble in the line.

Once again although the line is not vented properly, the line has a clog or, a belly! It is as HJ said held back by a positive air pressure in the line which is caused by a clog or, belly

- - - - - - - - - - - - - - - - - - - -

Since 1995 (3 years before Google started) PlumbingSupply.com has been THE best plumbing supplier on the web. Please visit our sponsor [www.PlumbingSupply.com]

OK there is a lot of responces here. Thanks for all.

Packy I have tried the Oatey version of your suggestion. hj is right I have an AAV installed. It did not work.

Krazyfx when I installed an air gap the dishwasher drained through it into the sink, then slowly down the drain. If I take the AAV out letting air into the drain line under the sink. The sink and dishwasher drains fast.

That is what confuses me. When you all say there is a clog. The drain runs fast and does not back up if I introduce a vent into the drain under the sink. Also the line doesnt backup if I insert a garden hose into the stub without the sink/dishwasher drain connected. Thus introduceing air. How would the drain line heading down to the basement concrete floor vent if it connects to the main stack under the basement floor? Unless the obsruction is between the pipe heading down to the concrete floor and the main under the floor in the basement. But, why won't water back up and come out between the space between the hose and the stub if clogged? Am I over thinking here?

Redwood mentioned a belly. I don't know what a belly is. Could you please explain?

we did not say you had a clog we said you had a restriction which can cause your symptoms. when you are inserting the hose you are most likely putting it on the other side of the restriction.

a belly will only be in a horizontal pipe and is where the pipe sags down

- - - - - - -

PLUMBERS "Protecting The Health Of The Nation"



Edited 1 times.

I can't be putting the hose on the other side of the resriction cause there is only one pipe under my kitchen sink. It leads down the wall and through the concrete. I am assuming then to the main drain which has the vent out the roof attached.

The belly makes sense. I would need to have someone with a drain camera take a look. Correct? I don't what to tear up the concrete in the basement without knowing for sure that a belly in the horizontal pipe is in fact the problem.

take the AAV out letting air into the drain line under the sink. The sink and dishwasher drains fast.

You are confused. When you remove the AAV you are letting air OUT of the drain and then the water can enter the pipe and flow. The air is caught between whatever is clogging the main line and your sink trap.

Unless this has always been a problem, it is not a belly in the pipe.