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Thread: Offset Sink Drains Slow

  1. #1
    DIY Junior Member k-auss's Avatar
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    Default Offset Sink Drains Slow

    Hello,

    I've just replaced a kitchen sink but it seems to be draining very slow now. Also, after reading some threads I think I might need to re-do the offset trap. The old setup was a two bowl sink plus disposal. My questions are;

    1 - Could this setup be the reason for a slow drain? All parts are new or have been cleaned, and it seemed to be fine before. This is also a new strainer basket, but with the strainer removed it is still pretty slow to drain.

    2 - Should I re-do the offset, so that it is tail-with-dishwasher/p-trap/horizontal/long bend/wye?

    Thanks for reading!

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  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    What you have looks fine.
    It may be that the second sink allowed more air, but there are plenty of singles plumbed that way.
    Normally you would have the p-trap under the basket, but in a two bowl sink, it looks more like how yours is.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    One possibility, unless the drain is actually partially plugged, is that that long pipe has a lot of trapped air that cannot escape if water covers the bottom of the drain fitting too quickly. It is exactly the same as a vessel sink without an overflow. With two sinks the second one acts as vent to evacuate the air.
    Licensed residential and commercial plumber

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    DIY Senior Member bluebinky's Avatar
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    Did you leave a rag inside the drain stub-out when you hooked everything back up?

  5. #5
    DIY Junior Member k-auss's Avatar
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    no I did not.. wait a minute, where's my other sock?

  6. #6
    DIY Junior Member k-auss's Avatar
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    Quote Originally Posted by hj View Post
    One possibility, unless the drain is actually partially plugged, is that that long pipe has a lot of trapped air that cannot escape if water covers the bottom of the drain fitting too quickly. It is exactly the same as a vessel sink without an overflow. With two sinks the second one acts as vent to evacuate the air.
    Ok, so based on your and Terry's response at least I don't have anything major to worry about like an S-trap situation. I guess if the drain-speed continues to bother after a while it isn't that difficult to try it as tail/trap/horizontal/bend.

    Thanks!

  7. #7
    Moderator & Master Plumber hj's Avatar
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    Stick a straw down the drain before you put water in the sink. if it still drains slow it is a clog problem, if it drains good it is a trapped air problem.l
    Licensed residential and commercial plumber

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    Can't tell from the photo...does that horizontal trap arm slope down some?
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #9
    DIY Senior Member Hairyhosebib's Avatar
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    Quote Originally Posted by jadnashua View Post
    Can't tell from the photo...does that horizontal trap arm slope down some?
    I agree with this question. Perhaps if the pipe had a bit more fall it might drain better.

  10. #10
    Moderator & Master Plumber hj's Avatar
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    That would have absolutely NO EFFECT on the drainage, unless it had so much back pitch that it created a double trap, which is not the case here.
    Licensed residential and commercial plumber

  11. #11
    DIY Senior Member Hairyhosebib's Avatar
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    Quote Originally Posted by hj View Post
    One possibility, unless the drain is actually partially plugged, is that that long pipe has a lot of trapped air that cannot escape if water covers the bottom of the drain fitting too quickly. It is exactly the same as a vessel sink without an overflow. With two sinks the second one acts as vent to evacuate the air.
    You already pointed out an obvious problem!! "THAT LONG PIPE HAS A LOT OF TRAPPED AIR" Flat pipes don't drain well. On the other hand I have seen some severely back pitched drains drain pretty good too. They just get plugged by all the stuff that gets put in the sink to drain out with the water. I have seen drains that seem mostly plugged do to the fact the water streaming out of the aerator on the spout was dead center to the center of the strainer basket. Once the spout was moved off center of the drain, the water could form that swirl and the water would then sound like it was getting sucked out of the sink. The guy might have a vent problem too. I personally think it will drain better if the trap is hooked up to a longer tailpiece and ran with a bit of fall to the wall connection.
    Last edited by Hairyhosebib; 07-30-2012 at 01:13 AM.

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