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Basin waste pipe gradient

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Hi
Just redoing my bathroom and I notice that the basin waste pipe is actually sloping up to the join with the bath pipe.
The small piece of pipe was wedged in to hold it and I can hear water from when last used.
Only way I can get a downward slope or at least level would be to make the join lower at the bath waste pipe (pic right).
Maybe could fit a flexible solvent weld pipe.
Any help appreciated.




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Comments

  • Mickey666
    Mickey666 Posts: 2,834 Forumite
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    Hmm.  It's certainly not an ideal arrangement but I don't see how making the join to the main waste pipe at a lower level is going to help.  Water in the pipe is not going to flow uphill!  Unless I've misunderstood.

    The main wastepipe looks to be just slightly below the bottom of the floorboard.  If the sink wastepipe can be propped up to reach the bottom of the floorboard then the sink wastepipe should be almost level with the main wastepipe anyway.

    The other approach is to just leave it as it is.  Yes, water will always be present in the sink wastepipe, but it would merely act as an extended 'trap'.  As I said, not ideal, but not a major disaster.  The main issue would be the increased possibility of 'crud' settling out in the sink wastepipe, which could eventually lead to flow and/or blockage issues . . . but it would take many years and there are many solutions to clear blockages.

    How long has the pipework been like this?


  • As Mickey asks, what happens when you grab the waste as it comes up the wall and pull it gently upwards until it touches the underside of the floorboards?
    That's probably the best you can hope for. If the bath/main waste pipe is fractionally below the top-of-the-floor-joist height - as it appears to be - then having the basin waste pipe tight against the underside of the f/bs will mean it'll have a gentle slope.

    Looking at that first exposed joist - where the grey bath waste turns to white - the top of the waste pipe appears to be a half-inch or so below the top of the joist? Can you confirm this is the case? Ok, looking at the next joist down, the waste appears to be higher - is that the case? If so, the whole caboodle is just bad.

    How far does that main waste continue before it goes through the wall, and at what height (relative to a joist) does it exit the room?

    Oh, and what's coming down the wall on the RH side to join into it?


  • danrv
    danrv Posts: 1,598 Forumite
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    edited 26 April 2021 at 6:36PM
    Mickey666 said:

    How long has the pipework been like this?
    Possibly since the bathroom was extended. Not sure when that was.
    70’s ex rental property so may have been done on the cheap.
  • danrv
    danrv Posts: 1,598 Forumite
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    edited 26 April 2021 at 6:46PM
    As Mickey asks, what happens when you grab the waste as it comes up the wall and pull it gently upwards until it touches the underside of the floorboards?
    That's probably the best you can hope for. If the bath/main waste pipe is fractionally below the top-of-the-floor-joist height - as it appears to be - then having the basin waste pipe tight against the underside of the f/bs will mean it'll have a gentle slope.

    Looking at that first exposed joist - where the grey bath waste turns to white - the top of the waste pipe appears to be a half-inch or so below the top of the joist? Can you confirm this is the case? Ok, looking at the next joist down, the waste appears to be higher - is that the case? If so, the whole caboodle is just bad.

    How far does that main waste continue before it goes through the wall, and at what height (relative to a joist) does it exit the room?

    Oh, and what's coming down the wall on the RH side to join into it?


    Main waste pipe is about 1cm below the floor level. The basin pipe is just loose since I disconnected it and is almost level if I it pull it up to the floor.
    The vertical pipe is surplus to requirements so will take that out and cut and cap the hot pipe 
    as that’s no longer needed.


  • knightstyle
    knightstyle Posts: 7,219 Forumite
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    If that is upstairs I would br worried about how much those joists have had cut out!  Would be worth having someone who knows about these things having a look.
  • danrv
    danrv Posts: 1,598 Forumite
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    edited 26 April 2021 at 9:36PM
    If that is upstairs I would br worried about how much those joists have had cut out!  Would be worth having someone who knows about these things having a look.
    Yes, someone else mentioned that.
    I could glue and screw some 18mm ply to strengthen the ones that need it.

  • Apodemus
    Apodemus Posts: 3,410 Forumite
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    Could you re-route the sink waste to run along the wall, then along behind the bath panel to angle down into the waste near where the bath waste pipe joins it?  Again not ideal, but the only way I can see to give you a consistent fall.

    I'm guessing the surplus vertical waste pipe and the capped water pipes indicate that the sink was originally on that wall - relocating it back there might be the best option.
  • grumbler
    grumbler Posts: 58,629 Forumite
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    edited 27 April 2021 at 10:02AM
    Apodemus said:
    Could you re-route the sink waste to run along the wall, then along behind the bath panel to angle down into the waste near where the bath waste pipe joins it?  Again not ideal, but the only way I can see to give you a consistent fall.

    This makes no sense as the as the pipe goes from the bath down ( top to bottom the 1st photo; letf to right the 2nd). The pipe near the bath can be only higher and the route to this point is longer.

    I didn't read all the comments, but I don't understand why the basin grey waste pipe (1st photo on the left) can't be lifted up to make the white pipe at least horizontal.


  • Apodemus
    Apodemus Posts: 3,410 Forumite
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    grumbler said:
    Apodemus said:
    Could you re-route the sink waste to run along the wall, then along behind the bath panel to angle down into the waste near where the bath waste pipe joins it?  Again not ideal, but the only way I can see to give you a consistent fall.

    This makes no sense as the as the pipe goes from the bath down ( top to bottom the 1st photo; letf to right the 2nd). The pipe near the bath can be only higher and the route to this point is longer.

    I didn't read all the comments, but I don't understand why the basin grey waste pipe (1st photo on the left) can't be lifted up to make the white pipe at least horizontal.


    I agree its not elegant, but despite the length of pipe-run you have sufficient height for a constant drop if you start at sink-trap level and work along the wall and down behind the bath panel to join the bath waste rather than going vertically down below the floor, then up to join the waste pipe.

    But unless there is a very good reason why the sink needs to be on that wall, I'd put it back across the room where it belongs!
  • danrv
    danrv Posts: 1,598 Forumite
    Seventh Anniversary 1,000 Posts Name Dropper
    edited 27 April 2021 at 6:23PM
    grumbler said:

    I didn't read all the comments, but I don't understand why the basin grey waste pipe (1st photo on the left) can't be lifted up to make the white pipe at least horizontal.

    Yes. That’s what I was going to do. I can put a wooden support between the joists to hold the pipe as high as possible.
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