New bathroom sinks drain slow

[Gus]

I recently installed new countertops in both my upstairs bathrooms. I replaced the sinks with undermount sinks, I also replaced the faucets. The new sinks are deeper than the old sinks so I had to cut the tail pieces to get the proper slope. But the new sinks still drain slow and back up into the other bathroom. The old sinks drained fine. What am I missing? Any help would be greatly appreciated.

 

[havasu]

I can't understand how cutting a tail piece would cause the back up. Are you sure you just don't have a blockage in your drain or vent?

 

[Gus]

The only thing that I changed were the sinks and faucets. There are 3 new sinks and they all drain slow after replacing them. There could be a blockage I suppose but they all drained fine before they were replaced.

 

[havasu]

Did you get any snow recently which could have blocked your vent?

 

[Gus]

No snow, but the new sinks have an overflow hole and the old sinks did not have that. Could that have changed the way the vent works?

 

[havasu]

No, the overflow hole, if anything will allow quicker draining due to the additional venting. I'm wondering if the new sinks are just an unusual design (square perhaps?) which stops the normal vortex action? Bear with us for a bit until we get some experts on here after they get off of work. I'm sure they will be able to help you alot more than I can.

 

[Gus]

The sinks are bowl shaped, undermounted below the granite.

 

[havasu]

Please help me in here guys!

 

[Gus]

Havasu, I think you are on the right track with the vent. If I loosen a p-trap on any of the 3 sinks they all drain. I just don't know what changed or how to fix it.

 

[havasu]

If this is the case, I would be looking closely at your venting up to your roof. It is not working and clogged, or your plumbing configuration has been done incorrectly and you don't have one.

 

[phishfood]

Did you by chance remove/change any drainage piping under the sinks? Say, an air admittance valve?

 

[Gus]

Did you by chance remove/change any drainage piping under the sinks? Say, an air admittance valve?

I dont think so. All I did was disconnect the old sinks and connect the new ones with the same equipment.

There is a rubber hose running from a wye on 1 of the p-traps into the wall. Possibly to the vent? It appears to be restricted a little. As soon as I get a chance I am going to reconfigure it to where it is unrestricted.

 

[phishfood]

Is this wye between the sink basin and the Ptrap, or between the Ptrap and the wall?

If the former, that sounds like a feed for a trap primer, and shouldn't be the cause of the problem.

If the latter, that sounds like some kind of "shadetree plumber" vent, and is most likely the cause of your problem.

 

[Gus]

It is above the p-trap between the sink tailpiece and the p-trap

 

[Gus]

Maybe this will help you out.

 

[havasu]

I believe the black "dishwasher" hose is the root of your problem. I believe Phishfood is correct as it looks like an antiquated wet vent. Reposition it so it has no kinks, and give it another try. I myself would blow into the hose to see if is partially clogged and if air flows without restriction.

 

[Mr_David]

Do you have an AC unit in a closet near this sink or in the attic above?
IT is most likely a condensate drain from the AC and has nothing to do with the vent.

 

[Mr_David]

Havasu, I think you are on the right track with the vent. If I loosen a p-trap on any of the 3 sinks they all drain. I just don't know what changed or how to fix it.

That is very odd.
You loosen it where?
At the top white slip nut on tail piece extension?
What's the sink look like.

You also said that one sink backs up into other sink in other bathroom.
Have the drain snaked out and then let us know how it works.

 

[Gus]

Yes, there is an AC unit in the attic near there. I can loosen the nut that connects the p-trap to the tailpiece and they will drain into a bucket. When I turn on the water in one sink I can fill them all 3 up.

 

[Gus]

Ok fellas, here is the update. I met a plumber today and he suggested trying Drano. He said that since the sinks were disconnected for a few days while my countertops were being installed the sludge in the drain could have hardened. I put Drano in all 3 sinks and now they are draining. WooHoo. Thanks for your help.