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Discuss Ballcock now driving me nuts in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. DripsnDropsBognor

    DripsnDropsBognor Member

    So i fitted new combi cylinder last year
    and replaced ballcock in tiny cold water storage tank at same time.
    Bank holiday weekend went over and changed both ballcocks both tanks share 1 overflow.
    Both shut off happy days.
    Phone call day to say water is ****ing out of overflow...
    Been over tested both ballCocks all seem fine bent them a tiny bit more just to make sure they shut off hard.
    Just had another call to say dripping again outside.
    Also noticed today top tank in combi was warm water to touch... think this is just conduction or thermostat failed?
    Any ideas?
     
  2. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    combi boiler on a non pressurised heating system ?

    or do you mean a cylinder
     
  3. DripsnDropsBognor

    DripsnDropsBognor Member

    Combi Cylinder economy 7
    Cold water tank in top cylinder in bottom part
     
  4. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    right its a fortec cylinder

    any outlets that have hot on mains ?

    eg mixer taps showers etc
     
  5. DripsnDropsBognor

    DripsnDropsBognor Member

    Hot on mains? Hot and mains would only be kitchen sink... everything else runs off c/w tank and cylinder boosted my shower pump
     
  6. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    boosted both hot and cold if so put some check valves on the kitchen sink
     
  7. DripsnDropsBognor

    DripsnDropsBognor Member

    You think mains is back filling cylinder from kitchen tap?
    Hadn't thought about that...
    More likely with showers tho no?
    Failed stat not more likely and backfilling that way?
    I need to go back and check...
     
  8. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    yea

    if there pumped equal pressures so not likely

    not after a year but worth checking but top tank would be warm
     
  9. DripsnDropsBognor

    DripsnDropsBognor Member

    Thank you very much definitely food for thought I will investigate both. I have had a few dodgy backer elements around the same time I fitted cylinder so need to triple check it's not backers I fitted
     
  10. Chuck

    Chuck Top Contributor!!

    Assuming you mean a 'Fortic' type combined cylinder...

    If the hot tank starts filled with cold water at, say 10°C and heats up to 60°C the water will expand by about 1% by volume. This amount of water will be driven up into the header tank and there needs to be space to accommodate it without the overflow running.

    If there is not enough expansion space the process will continue until the cylinder is full of hot water, a couple of litres will overflow in the process, and the header tank may have got somewhat warmer than normal as well.

    For a combination tank, normal expansion [0.02%/°C for the bulk expansion coefficient] is only going to raise the level in the cold tank by 15 mm or so. If the thermostat has failed (and there is no other cutout) the expansion will be proportionately more up to the point the temperature in the cylinder reaches boiling at which point a lot of steam will start being transferred up the vent and then out of overflow, with the rate limited by the heater power.

    So, if your top level is at least 15 mm + plus a bit for luck below the overflow and the ball-valve seems to be working well I'd suspect the thermostat.

    If it reached the point the cylinder was boiling I think it could be pretty noisy, dramatic and dangerous. I've never witnessed it myself. I have seen the aftermath of such an incident (in the 1970s) when a boiler hadn't cut out, the overflow hadn't coped, and there was a *lot* of damage to the house. There would have been a lot more power than an electric immersion heater but I've erred on the side of caution with thermostats ever since.
     
    • Like Like x 1
    Last edited: May 6, 2017
  11. DripsnDropsBognor

    DripsnDropsBognor Member

    Yes fortic cylinder type...
    Thank you I will investigate in the morning as I am paranoid about cylinders causing damage.
     
  12. Gasinspect

    Gasinspect Member

    I was always taught that Fortic needed copper float, not plastic. But kitchen tap if it is not divided flow in the spout could cause problem of backfilling. doubt it is a failed stat, you would soon know if that was the case!
     
    • Like Like x 1
  13. DripsnDropsBognor

    DripsnDropsBognor Member

    So no problem with fortic tank. Ball valve in there is fine.
    My problem now is with ball valve is tiny cold water storage tank.
    I have put 3 fudging ballcocks in it now and when left to its own devices it over flows. There is only 6 inches of water in it when I have fitted I wait for it to fill and stop which it does perfectly. However after 24hrs the overflow is dripping again...
    I know what I'm doing with ballcocks I have probably fitted 300+ but what is going on with this one?
    Can it be that I have fitted 3 faulty ones.
    1st one from my local regularly use and 2 from different suppliers but nothing solving so far. What else could it be?
     
  14. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    Are you sure it's the ball cock and not rising through the feed or vent
     
  15. DripsnDropsBognor

    DripsnDropsBognor Member

    Customer can hear constant dripping in cupboard and it is supplying cold water to toilet basin and shower. no vent pipes going into it... it has fortic cylinder next to it.
    I don't think it can be back filling from anywhere as all seems equal pressure.
    I have noticed mains pressure is only around 1.5 bar is this high enough pressure for high pressure seat?
    Could it be that part 2 ball valve is just too long and can't be adjusted enough to turn itself off and I need to fit a part 1?
     
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