Becorlac

Drainage in my bathroom sink has been slow to none for about 5 years. We replaced the sink and the pipes underneath, no help. The drain pipe ties into the main drain about 3 feet away and just inches above where the toilet joins. We have run a snake all the way into the main drain and found no clog. The vent has been checked and is clear. We had been using the sink with the plug in and bailing it out when it got full but anytime a sinkful was let out it initially appeared to drain then stopped. After plugging the sink again and bailing out the remaining water, pulling the plug again resulted in water raising back up. Recently we pulled the sink off again and the only evidence of water we found is in the P trap, further down was rust. What could cause the flow to stop at the trap?

BridgeMan

Sounds like there might not be adequate pitch in your drain line to empty the sink. Or possibly even a bit of reverse pitch, meaning you're asking the water to run uphill. A quarter inch per foot (minimum) is a healthy pitch to promote healthy flow in a sink drain, assuming your vent line isn't plugged. If you have the access, put a small torpedo level on the pipes to see what pitch you have.

Redwood

If you remove the trap and run water in the sink does water pour out of the sink tailpiece?

Becorlac

BridgeMan, when we tore out the wall the first thing I thought was it didn't look sloped at all. I checked the length of the drain pipe and it's 2' rather than the 3' I posted and at the same time I checked the pitch and it's 1/2" from the sink end to the drain end, 1/4" per foot, just as you said. When we replaced the sink, we only replaced the pipes underneath not behind the wall and I think those might be original to the house which was built in
1955. Because of that I pretty much dismissed the notion thinking the problem couldn't possibly have been going on that long.

Becorlac

Redwood, yes it does.

Redwood

Okay then the drain inside the wall is clogged despite your snaking efforts.
I'd venture a guess that the clog is at the tee where the drain turns to drop down and your snake bounced off the clog and went up the vent....

These can be fun even for an experienced drain cleaner....

Becorlac

Any idea why the multiple cleaners and decloggers and acid type products we've tried didn't help? And now......garden hose in the vent?

Redwood

Because they don't work and you need a drain cleaner with a snake to clean the line.