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Discuss Header overflow - should be so simple. in the Plumbing Forum area at

  1. Terry Godber

    Terry Godber New Member

    Header tank overflows.
    Has 4 connections
    2 x 18mm mm distribution both fitted with non return valve,
    1 x 15mm [pressure limited 4 bar] supply via ball valve,
    1 x 18mm overflow waste discharge to eaves.
    Also theres 1 x 18mm pressure releif line from cylinder cupboard which terminates over the tank. This has a jam jar suspended below it to prove its not discharging back to the tank - it's dry.
    The overflow discharges - usually overnight.
    The ball valve assembly has been replaced with new - more than once and with differing types to no avail - there are no obvious leaks at this point!
    Still there's an overnight discharge.
    HOW?? What else can possibly be wrong?
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Backing up through the cold feed check in the morning is the tank water inside the tank warm / hot
  3. Terry Godber

    Terry Godber New Member

    Hi Shaun,
    As they leave the tank the 22mm h and c distribution lines are fitted with non return valves. They serve down to a 2 bar dual pump which is off overnight to manage any noise issues.
    Water heating is controlled to times outside the overnight period so no reason for expansion issues during the night.
    System has been fine for 30 years. It is now recently causing problems but nothing has been changed for years save for the recent addition of non return valves and replacement ball valves and float assemblies.
    Heating is a sealed pressurised system and holds steady at about 1.5 bar, so no cross link leak otherwise pressure would vary.
    Aother point there's a ballofix in the 15mm supply close to the tank. If I isolate this the problem ceases. This factor points hard to the float valves but I have now fitted 5 with 4 differs and none have stopped the problem. No duffer could get all 5 installed to fail.
    One last point when installed I am setting the float arm to close off at overflow minus about 70mm so it's gaining gallons not pints to reach the overflow.
    Really, logic denies that this problem can continue but it does!!
  4. Terry Godber

    Terry Godber New Member

    Hi Shaun,
    Still in need of more help here!

    Header tank temperatures remain ambient - not warmer than surroundings.

    First fitted the non return valves on the distribution pipes just over a couple of days ago to be sure to prevent any back flow to the tank from them.

    There's still an ongoing issue except when I isolate the 15mm supply.

    Also, since installing the non return valves on the distribution lines and with the supply line ballofix open there's been about a half cup of water discharged [over 24 hours] to the container which I positioned under the distribution system overflow pipe [the one which vents and drains over the header tank and therefore one that could fill it].

    To my mind this suggests that there's minimal back pressure in the distribution side. Probably nothing more than that generated when shutting a ceramic tap off reasonably quickly against the operating 2 bar pump. Anyone disagree with this assessment?

    During this same time water levels in the header raised from minus 70mm to overflow - so again to my mind the water gain just has to be either via the non returns or via the float on the supply otherwise that small vessel [a small jam jar] would be full to overflowing and it isn't!

    Seems I may need to remove the non return valves again long term [any comments anyone?] but first I needed to confirm that there's been no significant backflow to the header via the distribution lines.
    Adding them seems to have made no obvious difference to the rate levels can build in the header tank so perhaps I just take them out again?

    HELP please!
  5. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    TBH you shouldn't need to install non return valves also best option is to get a plumber out to look at your system as its a unique
    • Agree Agree x 1
  6. Ian10261

    Ian10261 Plumber GSR

    Is there a branch between the ballofix and the ball valve?
    If so, where does it go to?
  7. Ric2013

    Ric2013 Plumber

    A distributing pipe feeds taps.
    A cold feed feeds a cylinder.
    Usine the definitions I have given, do you have 2 distributing pipes, or 1 distributing pipe and 1 cold feed, coming off that cistern?
    • Like Like x 1
  8. Terry Godber

    Terry Godber New Member

    Hi Ric2013
    There are two 22mm outlets leading from the base of the cw storage header to the cylinder cupboard at 1st floor. One serves cw feed to the hw distribution and the other is the cw distribution.
    In detail:
    From the cw storage 1 cold feed drops to the base of the coil in the immersion cylinder, then the h distribution runs from the head of the coil and connects to the h inlet of a two bar pump with the h outlet then re connected to the old distribution pipe again.
    The other cw distribution drops to the cw pump inlet and the cw outlet is reconnected to the distribution pipework.
    [Question - the pump is a dual pump h and c - is there potential for a backfeed from h to c via the pump assembly? Grasping straws - surely not as h is one end and c is the other so any transfer accross the pump motor zone blows the pump - unless you guys know otherwise!]
  9. Terry Godber

    Terry Godber New Member

    Hi Shaun
    To be honest I quite agree, but its proving to be time consuming to trap the fault and at the very least I need an engineer with the right approach, not another float valve.
  10. rpm

    rpm Trusted Plumber

    No transfer across the pump so rule that out.
  11. Terry Godber

    Terry Godber New Member

    Hi Ian,
    Why exactly do you ask? I am hoping you have a point here, in fact there is a mcw branch which tees off between the ballofix and the float.
    It tees off between and then runs over at high level before it then drops to serve a Redring Powerstream electric shower. The connection has been in place like this for a decade without issues and the Redring only has a cw supply.
  12. Terry Godber

    Terry Godber New Member

    Thought not...
  13. Ian10261

    Ian10261 Plumber GSR

    If, as you say the problem goes away when you turn off the ballofix then it follows that mains cold water entering the gravity system is the cause of the problem.
    It also follows that the problem lies downstream of the ballofix. If the ball valve is not letting by then its obviously going somewhere else.
    I was wondering if the feed to the sealed system filling loop was branched off after the ballofix, the filling loop was letting by, the gauge had stuck and the cylinder coil had failed. A long shot i know but stranger things have happened and 30 years is a good age for a cylinder. I've known them to fail well before that age.
    Problems like this can be very hard to pin down but mains water is definately getting into the gravity fed side somehow and then backfeeding into the cws. Have a good look at that branch pipe again and see if there is anything else it feeds into.
    Hope this helps.
    • Disagree Disagree x 1
  14. Terry Godber

    Terry Godber New Member

    Hi Ian,
    Testing a potential solution... years earlier the original feed to the ensuite was gravity via a line teed off the side of the 18mm cw gravity feed at 1st ceiling level.
    Later the Redring was introduced [at the time the pump was not in place] and no surprise the flow was inadequate so a separate mains feed was then introduced.
    At this stage the gravity feed and the mains cw feed were linked via a ballofix isolator before the shower unit, thinking one day I will add a pump.
    Problem may well prove to be that because the ballofix was first to isolate the gravity feed the mains pressure connection to the ballofix was then reverse flow. Over time it has been OK and unused [closed]. I did operate it a little while back [just to stop it seizing I thought] but now when I come to it today, it leaks at the slotted screw but only when its turned again.
    Right now its removed and relevant connections are terminal capped leaving the mcw feeding the shower and removing the interface.
    Hopefully, I will let you know that my issue has been fixed in a couple of days. Any way thanks for your question which may well have rattled the right chain...
  15. Ric2013

    Ric2013 Plumber

    If I understand you:

    You have a working spring loaded one way valve (a proper check valve, airtight, not a flap valve that is only ish) on the cold distributing pipe, so we can rule out problems with mixer taps backfeeding up the cold distributing pipe.

    You have a similar valve on the cold feed to DHW cylinder, then that rules out split coil and mixer taps passing water back up the cold feed.

    The water can now only get into the cylinder from the top: the vent and the fill valve. Since the vent is only allowing a few drops of water through, we can assume that is normal expansion of water and not a punctured coil or mixer issue causing backfeeding through the DHW cylinder and vent pipe.

    At this point, either you have a very leaky roof, or the water is coming in through the ballcock, impossible as it may seem.

    Do I understand correctly, Terry?

    If so, at this point, use a 15mm blanking cap on the tap connector that normally goes onto the ballcock and, if the level of the water does not rise overnight, I'm right, as by capping the ballcock, you aren't affecting anything else. If the level still rises, I'm missing something.

    Final thought: is the overflow shared with something else and the cistern is filling through the overflow?
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