I replaced my old bathroom sink with a new pedistool sink and I used the old PVC drain conections. The new sink fills up and will not drain properly. When I loosen one of the nuts, air releases and the sink drains. There are no clogs and/or pipe blockages. What is causing the sink to backup and only drain if one of the pipes is loosened, which then leaks? I have taken it apart four times and it happens every time I put it back together.

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Originally Posted by PhilPA123

I replaced my old bathroom sink with a new pedistool sink and I used the old PVC drain conections. The new sink fills up and will not drain properly. When I loosen one of the nuts, air releases and the sink drains. There are no clogs and/or pipe blockages. What is causing the sink to backup and only drain if one of the pipes is loosened, which then leaks? I have taken it apart four times and it happens every time I put it back together.

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... have an overflow where air could have vented into allowing it to drain properly and the new sink not have an overflow?
If this is true, then something is amiss in your plumbing drain/vent system that is not allowing air into the bathroom sink drain thus preventing it from draining.

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Originally Posted by PhilPA123

I replaced my old bathroom sink with a new pedistool sink and I used the old PVC drain conections. The new sink fills up and will not drain properly. When I loosen one of the nuts, air releases and the sink drains. There are no clogs and/or pipe blockages. What is causing the sink to backup and only drain if one of the pipes is loosened, which then leaks? I have taken it apart four times and it happens every time I put it back together.

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You could check the lavatory vent to make sure it's not blocked but it sounds more like a blockage to me. Have you ran a snake through the lateral drain, ( the horzontal line in the wall) to make sure it's clear? Unless there's something blocking the flow, gravity alone should force the water in the lavatory past the trap and into the lateral drain even if the vent's blocked. It's weird but I keep thinking "vent problem" because when you open up the trap you're venting the discharge. Snake out the lateral and get back to me. Regards, Tom

I did run a snake into the wall and down. Nothing seems to be causing the back up. I messed with it again last night. If I loosen the PVC nut that is attached to the pipe from the wall, I hear air escaping and the sink will drain down. It will drain very slowly when everything is attached but I filled the sink and it took about a half an hour to drain. Could the run from the wall and the PVC extension to the trap be to long? It is only about an inch longer than what was on the old sink.

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Originally Posted by PhilPA123

I did run a snake into the wall and down. Nothing seems to be causing the back up. I messed with it again last night. If I loosen the PVC nut that is attached to the pipe from the wall, I hear air escaping and the sink will drain down. It will drain very slowly when everything is attached but I filled the sink and it took about a half an hour to drain. Could the run from the wall and the PVC extention to the the trap be to long? It is only about an inch longer than what was on the old sink.

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Code maximum is 5' but this shouldn't have a great influence on it draining unless it is very long and is not sloped to allow gravity to govern the drainage.

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Originally Posted by PhilPA123

I did run a snake into the wall and down. Nothing seems to be causing the back up. I messed with it again last night. If I loosen the PVC nut that is attached to the pipe from the wall, I hear air escaping and the sink will drain down. It will drain very slowly when everything is attached but I filled the sink and it took about a half an hour to drain. Could the run from the wall and the PVC extention to the the trap be to long? It is only about an inch longer than what was on the old sink.

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The lavatory isn't venting. You're venting it by hand when you loosen the compression nut. Check the vent to the fixture to make sure it's clear. Little by little you're eliminating the causes one by one. Keep on checking and you're bound to run into it. My bet's on the vent. Regards, Tom

If you changed the trap all the way to the wall when you chnaged sinks... did you leave the pipe that goes into the wall too long... thus cutting off the vent line when its pushed all the way into the fitting...


You may have to trim that pipe back a little so as not to cut off the vent... just a thought

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Originally Posted by PTflyer

if you changed the trap all the way to the wall when you chnaged sinks........did you leave the pipe that goes into the wall too long....thus cutting off the vent line when its pushed all the way into the fitting.......


you may have to trim that pipe back alittle so as not to cut off the vent.......just a thought

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This would choke off the vent assuming it is where it should be, 90 up from the drain.