Sink slow to drain

[Tel77]

I've just finished re-fitting my bathroom which included a new sink with vanity unit however the sink seems really slow to drain now.

I've fitted a new anti-vac connector to the waste incase the old one is sticking but doesn't seemed to have made too much difference.

I did move the pipework back behind the false wall so it was hidden inside the vanity unit so it now goes directly backwards from the waste trap before turning through 90 degrees and then drops approx 2 ft before turning back on itself through 90 degrees.

Is there anything I can do or am i going to have to accept that the sink is slow to drain?

 

[Tel77]

I'm convinced that it's a vacuum problem now as when I manually push the pin up on the anti vac valve to let some air in the water flows freely but struggling to know what to do next as I've tried a new valve.

 

[Charnwood]

The anti-vac valve is there to prevent the vacuum effect sucking the water out of the trap (or to prevent gurgling), which will only happen when the water has all left the basin. Manually opening it should have little bearing on the draining of the basin.

Pics would be helpful.

 

[Tel77]

Thanks for the reply. I'll try and get some pics but there's a limited amount that is visible now the wall is tiled and sink fitted.

I'm sure when I did a trial fit before tiling it was ok but for some reason it's started to do this. The old sink also didn't suffer from this and all I've done was extend the pipework slightly under the fllorboards and the bought the pipe vertically before coming back through the wall.

This really has got me puzzled

 

[Space cat]

when I manually push the pin up on the anti vac valve to let some air in the water flows freely

Are you sure you were letting air in? The valve will do that without your help. I think you have an airlock and what you're really doing is letting some of it out. All you would need to get an airlock would be a slight upward slope in the pipe.

 

[zanwan]

I went out a couple of weeks back to deal with the exact same problem. Basin was slow to drain. Checked traps etc, they were clear, looked almost new. However the pipework was a mess. went out the waste horizontally about a foot, then down, below the toilet cistern, then up again about 4 inches

yep, i said up lol, then connected onto the stack. The guy who done it was a professional carpenter But end result was water very slow to drain due to repeated air locks forming. Solution? Not worth the cost, hassle and headache.

Easiest way to get the water flowing fast is to plug the basin, fill it up, release the plug and let the water under its own weight force itself through, clearing the airlock.

You'll probably have to do this once a day but the water should drain quicker for a while, until airlock forms again.

 

[Tel77]

makes sense that it's an airlock but I was careful about trying to make sure the pipes were sloping down away from the trap and then downwards when under the floor boards.

I tried filling the sink and letting it drop on it's own but doesn't seem to have helped

 

[Tel77]

I'm really pulling my hair out now as I've even gone to the extreme of adapting the anti vac valve by extending the pipework higher and leaving it vented to allow max air escape but still the water backs up and tries to come out of the top of the temporary hose I put in.

Is there anything else I can try before I start ripping the sink back out bearing i mind the wall and floor is now tiled and pipework concealed?

 

[Nige F]

You need to find out where the waste pipe Ends and how long it is from the ending and your basin

 

[Tel77]

from what I can work out, the waste from the sink goes down under the floor and accross to join the soil stack which sits behind the shower tray in a false wall about 10ft away.

I've added some images so you can see the layout.

Untitled

• Tel77
• 10 Mar 2012
• 1

Untitled

• Tel77
• 10 Mar 2012
• 1

 

[HERTS P&D]

Clear it with: a snake, wet vac or air pressure gun.

Andy

 

[Tel77]

I don't believe the problem is with a blockage but more likely an air lock as the sink drained fine before the renovation and the waste pipe hasn't had anything down it during the work.
Also, if I gently lift the anti vac valve of it's seat to allow some air in/out then it drains fine.

 

[Space cat]

Maybe the pipe has sagged into a loop under the floor. How many supports did you put in?

 

[Nige F]

Thanks for the pics. Was a Durgo ( aav ) fitted on the soil stack behind the shower During the renovation - or does the pipe go through the roof to an open vent

 

[Tel77]

I guess the sagging may be an option but I'd be surprised as all I've done is extend the pipe by approx 1ft under the floor so that the pipe comes behind the wall rather than in front of it.

As far as the soil stack goes, I think it's vented out through the roof.

The bit that's puzzling me is that it worked fine before the renovation and I also did a trial fit of the sink before I tiled so that I could test the pipework and it seemed ok.
It's looking like I'm going to have to take the sink back of the wall I guess.