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slow draining bathroom sink

Discussion in 'Plumbing and Central Heating' started by danseagrave, 17 Feb 2007.

  1. danseagrave

    danseagrave

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    Location:
    Leicester
    Country:
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    Hello all,

    First a quick thanks, I've been lurking here for 6months and have learnt a lot, cheers! :)

    Now I've got one that I cant easily solve.

    We recently moved into a new (to us) house and have had a persistently slow draining bathroom sink (tried

    the usual ). Recently it has gotten really slow (half full takes > 2min). So today I took the trap off

    and, as expected, it was empty.

    I've drawn a picture to describe the setup (better than me trying to explain):

    [​IMG]


    From what I can tell the pie that goes down parallel to the wall is old - before this sink was installed.

    It may have been pushed down to fit the new compression fitting coming off the trap. Picture - the

    output of the trap joining the old downpipe:

    [​IMG]


    I've tried poking some old stiff washing line (all I had too hand) down the downpipe while I had the trap

    off. It seemed to get all of the way to the just before the 90-degree bend before getting wet.


    I've got a couple of questions:

    - do you think the slow drain could be caused by the old downpipe being pushed down to meet the new

    fitting?

    - what could I try to do to fix this?



    If there's anything you need me to do to help diagnose this I'd be grateful.

    Thanks
     
  2. Bahco

    Bahco

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    Sounds like a blockage further down the line somewhere.

    Your trap should however be full of water so it is losing its seal somehow.

    Could be the soil pipe has an aav stuck and not allowing air in to prevent negative pressures.

    Try an anti vac trap first which will prevent smells coming back into the room and investigate possible blockage :D
     
  3. TicklyT

    TicklyT

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    If the vertical pipe has been pushed down to line up with the new trap it is possible there is no longer any fall on the horizontal run, which will lead to the pipe becoming blocked, and standing water in the run may draw the trap as it flows away slowly.

    Does the pipe spring back up if you disconnect the trap?

    If it does, you could consider removing the push-fit elbow from the top of the pipe, and trimming it down to the correct height to restore the fall and re-fitting, or replacing the P-trap and elbow with an S-trap, again cutting the pipe to the correct height.

    Whilst everything is apart you may get better access to poke at any blockages under the floor

    First of all though, make a contingency plan - what would you do if the vertical pipe pulls out of a concealed push-fit elbow under the floor :eek:
     
  4. danseagrave

    danseagrave

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    Thanks guys,

    some clarification: "the trap was empty" Sorry, I meant that there was no blockage - there was water.

    The sink drain does smell, even though the trap contains water and I washed the general scum out yesterday. I assume this isn't right?


    How would I check this, where would the aav be? (and, btw, what is an aav - I assume it's some sort of "Anti-something Valve")

    Yes, it springs backup and towards the wall.

    OK, how would I go about doing this? "push-fit" suggests to me that I just need to pull hard enough :)

    Is there anything you can suggest I try to test if the problem is the angle of the horizontal run before I consider buying stuff and "hacking away at the pipe" :) ?

    I'm guessing the horizontal shouldn't have water in it?

    Thanks for the warning. fortunately the joint under the floor isn't entirely inaccessible. There is a fairly large hole bellow the pedestal and I can fit my hand around the elbow. - As an aside, when I did this I felt some pretty manky brown goop that has accumulated over the years. Running water though it now there is a slight leek - cloud this be because the push-fit joint constantly contains water?

    I have though about trying to replace the entire run, from sink the the soil stack outside. But I'm concerned that it is far bigger job than I really want to get into at the moment. The bathroom floor is lino glued onto those new style "big sheets of chipboard" floorboards. the floorboards seems solid all the way under the toilet & bath (no convenient joins).

    thanks for your help
    Dan
     
  5. Bahco

    Bahco

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    I would not mess with it personally.

    Renew the lot with an anti vac trap for about £10 and do a new run with a fall of 1 inch per metre keeping the waste pipe above the floor and out the wall to the soil stack if poss :D
     
  6. Lee-King

    Lee-King

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    Correct.

    If you undo the trap and it springs up as you have said, then don't worry about cutting it. If you have enough play on the waste pipe to pull it up further (giving you the extra fall that it sounds like you need) you won't be causing yourself any majour problem if you cut it to suit.

    Correct.

    Quite possibly. There are not designed to hold water, just to let it pass without leaking. Another possibillity is that the elbow could be not quite pushed on enough.
     
  7. danseagrave

    danseagrave

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    Thanks for the advice guys.

    I'm erring towards cutting the down pipe to height rather than replacing the entire run. The only way I could replace the run in a tidy manner (w/o going under the floor) would be to take the waste behind the (T&G) bath panelling which introduces a bunch of other, mostly time related, issues (i.e. the potential redecoration of the whole bathroom in six-months time).

    Bahco: Why do you suggest against messing with the old pipe work?

    Thanks
     
  8. Bahco

    Bahco

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    Because it is easier to renew the lot rather than faff about.

    You will know there is no blockages too.

    For the sake of a tenner, job done. :D
     
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