Shower drain blocked - out of ideas

Discussion in 'Plumbers' Talk' started by Albs123, Jan 12, 2021.

  1. Albs123

    Albs123 New Member

    Hi All,

    After some advice regarding my shower drain. It's draining extremely slowly, to the point where if I don't turn it off mid shower it will overflow from the tray. I've tried over the counter drain unblocker, baking soda, plumber's snake, plunger and it's had a whole bottle of one shot (sulphuric acid).

    It's a strange one, if I give it a good plunging then it'll clear and drain perfectly for as long as I leave it on. But then if I turn the shower off and come back to it later once it's all settled, say 30 minutes or so, the clog is back and it stops draining.

    Does anybody have any other suggestions for me? Running out of ideas now!

  2. Teki

    Teki Screwfix Select

    Is there a sink in the bathroom and does that drain Ok?
  3. Albs123

    Albs123 New Member

    Yes there is a sink and it's draining OK.
  4. Teki

    Teki Screwfix Select

    Probably the layout of the shower drain pipework causing a blockage. You've already tried some aggressive chemicals and methods for unblocking!

    You could try removing the plughole and using an borescope to inspect down the pipework.

    Smartphone borescopes are fairly cheap.
  5. Wayners

    Wayners Screwfix Select

    Run water and plunge at same time. Really enthusiastically. Tend to bring up black gunk and hopefully balls of hair to pull out. Plan B.
    Drag the hose pipe in. Wrap a sponge around the end of hose and (get tap operator and shout on) turn on blasting in plug hole while sealing with sponge forcing water through..

    Water should run through from hose at some rate.. You know its good then.

    Once a year I do all the plug holes in house with plunger masking up overflow hole then get the hose pipe in. Summer job really

    Buy a good large end plunger..

    I've never got on well with those pipe cleaners
  6. terrymac

    terrymac Screwfix Select

    Did it ever drain properly ?
    Can you get access to the shower trap from below ?
  7. goldwise

    goldwise Active Member

    Try a 'Sink & Bath Unblocker' from Screwfix. Item 13894 / £2.99. Unlodged a hairball the size of a golf ball from my shower drain a couple of years ago after all other methods failed.
    Kingscurate likes this.
  8. Severntrent

    Severntrent Screwfix Select

    Sounds as if the outlet pipe has a slight rise and fall in it somewhere along its length which causes a a bubble of air to be stuck in the upper section of pipe thus reducing the effective diameter of the pipe and restricting the flow. When you plunge it the bubble is forced out and the pipework acts as a syphon pipe which increases the capacity of the pipe so it is able to cope with the incoming shower flow. When you stop showering the pipe eventually empties to its initial state of play and air is able to return to the highpoint and the process repeats itself when you next shower. I attach a Micky mouse diagram to clarify (hopefully) IMG_20210112_230347172.jpg
    Last edited: Jan 12, 2021
    kiaora, Deleted member 25896 and Teki like this.
  9. Wayners

    Wayners Screwfix Select

    I took ceiling out to fix the waste pipe rise on one job. Plumber never turned up to fix so I did so won't forget that..
  10. I'd put my money on Severntrent's answer, seen exacts same problem a few times. Fabulous sketch btw, you're wasted as a plumber!
    Severntrent likes this.
  11. Severntrent

    Severntrent Screwfix Select

    Oh if only I was that rich
  12. DamoHutchinson

    DamoHutchinson New Member

    I experienced a similar problem a few years ago. Turned out to be a frozen downpipe slowing down the water flow. That's always worth checking too with the recent cold days we've had

    As for the hair in the plughole, after my partners been in it's like pulling an animal out every few months
  13. Severntrent

    Severntrent Screwfix Select

    But on plunging things run ok and ice soon melts if warm water is running through it?
  14. kiaora

    kiaora Screwfix Select


    As severntrent’s magnificent drawing shows, if you have two traps on a waste pipe,

    it will simulate a blockage and when plunged it will act as a syphon.

    Good luck

    Albs123 likes this.
  15. Severntrent

    Severntrent Screwfix Select

    Amended diagram to reflect kiaoras comment re 2 waste traps which I think is a more likely scenario as it is more probable that a run of pipe has dropped/ drooped over time due to poor installation than somehow developing an upward kink. OP doesn't say if things use to work ok and problem developed over time or its always been that way?
    Albs123 and kiaora like this.

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