Posting a message to the forum will remove the above advertisement
  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Checkout our Plumbers Insurance area - heavily discounted Public Liability Insurance and Van Insurance specifically designed for plumbers.

Discuss Cistern Water Suppy Issue in the Plumbing Forum area at

  1. Plumb37

    Plumb37 New Member


    I’ve just replaced my WC cistern fill valve (bottom feed) with a brand new one from Toolstation as the cistern wasn’t filling up. The water feed to the cistern has an isolating valve which seems to be working fine.

    After fitting the new valve the cistern filled up and flushed 4/5 times as it should do but then just stopped filling up reverting back to the original problem.

    Before fitting the new fill valve I changed the washer in the original one and the same thing happened.

    This makes me think there must be an issue with the water supply coming in but I have never seen a cistern fill correctly 4/5 times and then stop filling.

    Any advice would be really appreciated.
  2. rpm

    rpm Trusted Plumber Top Contributor!!

    Check the float isn`t getting snagged on anything in the cistern.
  3. Plumb37

    Plumb37 New Member

    Thanks for the reply.

    The float is ok and there is plenty of clearance. I had the same issue with the original fill valve & float which is why I changed it. I thought this may have solved it.
    What’s confusing is it all works as it should do for 5 flushes and then the water pressure seems to drop and it trickles.
  4. rpm

    rpm Trusted Plumber Top Contributor!!

    Guess you need to trace back to where the water is supplied from.
    • Like Like x 1
  5. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Who the manufacturer of the valve ?
  6. Rob Foster

    Rob Foster Top Contributor!!

    I wonder if this cistern is tank or mains fed > if its mains fed then it should refill grand style however if its a tanky one then this might be the answer.send us some pics hey
  7. DAVE01

    DAVE01 Member

    Best thing to do is put a penny valve on cold supply to cistern close penny valve turn back on to see if there is a issue with water supply If cold to cistern and its a standard ball cock it should have a low pressure orfice if its comeing from cold mains should be high pressure orfice use a torbeck valve it comes in a kit with high and low pressure and medium pressure orfice
  8. Best

    Best Trusted Plumber Top Contributor!!

    Most plumbers now don’t use the Torbeck valves as they started to give a lot of trouble when they were redesigned.
    Fluidmaster Pro45b (brass tail) is one of the preferred valves
    • Agree Agree x 3
    • Like Like x 1
  9. Plumb37

    Plumb37 New Member

    Thank you for the responses.

    This is the valve I fitted:

  10. rpm

    rpm Trusted Plumber Top Contributor!!

    Nice valve, I'm happy to fit them
  11. Last Plumber

    Last Plumber Trusted Plumber GSR Top Contributor!!

    Perhaps there is a foreign body in the supply to the valve?
    • Agree Agree x 1
  12. Plumb37

    Plumb37 New Member

    Thanks I’ll check that.

    It’s strange how the original fill valve and float filled the cistern a couple of times and then stopped to a trickle. Then the brand new fill valve in picture above filled the cistern 5 times and then stopped working.
    Two completely different valves doing the same thing so can only be the cold water supply.

    What difference would it make if it’s mains fed or tank fed apart from pressure?

  13. Plumb37

    Plumb37 New Member

    Really good quality and easy to fit.
  14. Plumb37

    Plumb37 New Member

    Thanks for your reply.
    The cold feed has a isolating valve already fitted which I turned off to fit the new fill valve and float. When I turned it back on the cistern filled within a minute and worked for 5 fills and flushes. After that its lost pressure and now is not filling. I can’t understand how it can work and then stop with a constant supply.
  15. rpm

    rpm Trusted Plumber Top Contributor!!

    Mains fed should give a constant feed however if it is tank fed then perhaps, just perhaps the problem is there.
    Try holding the float down and keep it down and flush the cistern when the water is high enough - I expect the water to stop entering the cistern after your 5 flushes and the fault lies within the tank feeding the cistern.
Similar Threads - Cistern Water Suppy Forum Date
Concealed Grohe Cistern Leak? Plumbing Forum Mar 11, 2019
Upside down cistern fill valve.. Water Regulations Feb 26, 2019