Recurring blockage.

Discussion in 'Plumbers' Talk' started by longboat, May 13, 2019.

  1. longboat

    longboat Well-Known Member

    This is something I've never seen anywhere. The blockage only effects the hot supply to the bath/shower thermostatic mixer valve and i first noticed it about 6-7 weeks ago when the flow from the tap gradually slowed to a trickle over a few days until it became useless.
    I removed the valve to find a yellow fatty substance blocking the filter in the hot inlet to the valve.
    I thought it a bit strange at the time but just removed it and re-fitted, and all worked well.
    Thing is it happened again tonight as i noticed the bath filling up slowly when running it for the kids.
    Removed the valve and here's what i found.
    20190513_200627-1-1.jpg 20190513_200744-1-1.jpg 20190513_210359.jpg 20190513_204429-1.jpg
    The first pic shows the material as i found it on the filter and the second one after removal.
    On closer inspection it felt a bit gritty so i dried it out and it appears to be like a very fine sand, as shown in the later pics.
    It is only this tap/valve that has been affected by this blockage and as i have taken a supply (several years ago without any problems until now) from below the bath to feed an outside tap at the rear of the house i can only assume that the check valves have become knackered for some reason and no longer work as they should.
    In twenty-odd years I've never come across this problem before.
    Have any of you lot, by any chance?
  2. chippie244

    chippie244 Well-Known Member

    Is it sediment from under the bridge?
    goldenboy likes this.
  3. ecoplumbing

    ecoplumbing Active Member

    Never had that kind of sediment , found plenty of boss white where previous plumbers have been a bit generous on fittings which has worked it's way through the water supply. Is the hot water fed from a cylinder? That'd be the first place I'd investigate
  4. longboat

    longboat Well-Known Member

    No, its a combi boiler. As i said, I've never seen it before either.
    The first time it was a bit of a "WT' moment, until it happened again several weeks later.
  5. longboat

    longboat Well-Known Member

    The devil makes work for idle hands.
  6. chippie244

    chippie244 Well-Known Member

    Have you not got much on then?
  7. longboat

    longboat Well-Known Member

    You can take the man out of the theatre, but you can't take the theatre out of the man.
    Great days, eh?
    KIAB likes this.
  8. KIAB

    KIAB Well-Known Member


    Well I've never seen that before.
  9. ramseyman

    ramseyman Active Member

    The first photo definitely looks like some kind of algae which can form even in anaerobic conditions. Wonder if that is what it is, Would probably be binding itself to any sediment in the pipework which is why you get the gritty stuff on drying out.
  10. The Teach

    The Teach Well-Known Member

    Could be a few reasons but maybe consider temporarily using the bath mixer without the filter just to flush out any debris hanging around.

    which gas combination boiler do you have ?
  11. longboat

    longboat Well-Known Member

    Its certainly got me stumped.
    It has got a kind of fatty appearance when wet but after drying it looks exactly like very fine grains of building sand.
  12. chippie244

    chippie244 Well-Known Member

    Billy Goat Gruff is having a laugh with you, have you had any phantom phone calls?
  13. longboat

    longboat Well-Known Member

    The feed to the outside tap is tee'd off from below the hot supply to the mixer which is why i initially suspected a fault in the check valves. How any back flow could occur, i don't know as it's never been drained down from there.
    Its a potterton promax he. A very good boiler from my experience.
  14. Heat

    Heat Well-Known Member

    Not sure what that could be.
    I wonder is there sediment on the walls of the inside of pipes?
    Another thought, - does the bath mixer have flexi hoses connected to it? Although I would think bacteria growth would not be gritty
    longboat likes this.
  15. CGN

    CGN Well-Known Member

    Any digging up of water pipes nearby?
    longboat likes this.
  16. Pollowick

    Pollowick Well-Known Member

    Do you have a water softener - maybe something from that?
    longboat likes this.
  17. koolpc

    koolpc Well-Known Member

    Looks like elephant snot. You got an elephant in the system!!!
  18. longboat

    longboat Well-Known Member

    Its weird alright.
    If it had only occurred once i would have forgotten about it by now, but twice in as many months has certainly got me thinking.
    Its blocking the inlet to the valve so its definitely coming from the supply side.
    I did wonder about the possibility of grit/dirt entering the mains supply to the house because of external work carried out by the utility provider as CGN has suggested, although i would have thought that such a scenario would also effect the cold supply as well.
    As its only the hot, i can only think that the outside tap is somehow trickling in this sediment, or, that maybe the heat exchanger in the boiler could be causing it by slowly releasing particles of scale on the heat exchanger into the system.
  19. longboat

    longboat Well-Known Member

    Not that im aware of. There's be no interruption to the supply.
    CGN likes this.
  20. longboat

    longboat Well-Known Member

    No. We live in a soft water area so no need.

Share This Page