AAV or air gap

[adiner]

Hello,

I recently resolved water backing up into the dishwasher by forming a high loop with the drainage tube. Now that that's solved, I am still having a problem with drainage from the kitchen sink. I have disassembled the trap (it's a grandfathered s trap since house is a ranch built in 1953) and there aren't any clogs nor coming from the garbage disposal. When I turn on the garbage disposal, it seems to improve the drainage somewhat, though not all the time. So, my question is, should I install an air gap or just install an AAV? I don't think the main stack has any problems, though another bathroom sink (also an s trap) is slow draining. Research suggests that the air gap is strictly to improve dishwasher drainage, so I don't know whether to go with the AAV or whether there is some other issue I should consider.

Any help would be greatly appreciated.

 

[Mr tee]

The drain needs to be cleaned.

 

[Sponsor]

 

[Terry]

And S-Trap is supposed to be vented below the floor, sort of like a shower drain.
And Air-Gap is to prevent the water from the kitchen sink from winding up in the dishwasher.
A vent or AAV (Auto Air Vent) is to prevent the p-trap from siphoning dry. The trap is there to provide a water seal to prevent sewer gas from entering the home. If the drain is slow, then it may need to be snaked.

 

[Reach4]

Neither an air gap nor an AAV will make a dishwasher drain better. The air gap is there to let water out from the piping under failure conditions, and the AAV is to prevent smells from a trap siphoning dry.

Do you have a basement? Can you see the drain pipe under the kitchen sink? If so, there may be a fairly simple solution. A common place for your drain under the kitchen sink to clog is where the flow switches from vertical to horizontal, and that may be under the basement floor.