Strange Kitchen Sink Problem

Maybe your sink roof vent is clogged causing an air lock

lovetotow wrote:
Maybe your sink roof vent is clogged causing an air lock

X2.Try running some water down the roof vent to clear any clog.

Does trying everything include disassembling the drain pipe?

bren99 wrote:
I have let it sit a couple days and I look and the water is gone....The sink is either clogged or it isn't, so why does it suddenly drain all the water out?

How would you know it suddenly drains out unless you sit there and watch it? I must be missing something.

I was thinking it might have something to do with something like that- air lock but had no idea what to look for. I will try the roof vent thing. Will let you know.

2oldman- No, I didn't sit and watch it continuously. Suddenly may be a poor choice of words, but I would look at it one minute, the sink is a quarter full of water and a half an hour later I would look and the sink would be empty. And yes, I did take apart the drainpipe. Thank you for your input.

Find your mechanical plumbing vent, usually at kitchen sink or bathroom sink. $ 6 at Lowes.
Problem solved

If it's in an island there is an air vent under the sink. Remove that and see if it works. If it does go to Home Depot and purchase a new one. Good luck.

When was the last time the gray water tank was emptied?

AAV (air admittance valve) under the sink if not working sink won't drain properly

Okay, maybe a dumb question but I've seen this topic go around RV message boards too many times with people smacking their heads once they learn - you don't have a separate galley gray tank do you?

Does the sink drain ok if you try slowly running water into it when empty vs. trying to drain a full sink full of water? That might help determine if it is a vent pipe problem. You say you took apart the drain pipe but did you try running a snake through the pipe and into the holding tank to see if there is a clog in the portion you did not take apart? Usually, about all you can take apart is the trap so that leaves a lot of pipe between there and the tank that could be clogged. If it is not clogged then it has to be a vent issue.