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Water Tanks Overflowing

Discussion in 'Plumbing and Central Heating' started by Y5Stu, 24 Sep 2007.

  1. Y5Stu

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    Apologies, I know similar questions have been posted before but as a non-diy person this problem is starting to get me down, here we go...

    Two water tanks in the loft, large and small, each with their own overflow pipe to the rear of the property, both the ball cock things appear to shut the water off and I have bent the arms slightly to get better closing pressure. I took several bucket loads of water out of of the small tank as it was overflowing and went away for the weekend, the central heating and hot water were on via the timer. On our return the small tank was full again, well over the ball cock and water coming out of the overflow.

    How/why is water entering the small tank, what could be causing this?

    Although it did not happen on this occasion I believe that the large tank also fills up past the ball cock and out of the overflow but this reduces when taps are opened, again why would this be?

    Central heating boiler is five years old, the rest of the system is approximately ten years old.

    Any advise would be appreciated, thank you.
     
  2. JohnD

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    You have a hot-water cylinder fed from the boiler, right? Is it fairly old and does it show any signs of leaking e.g. round the connectors?

    Looking at the water level in the small tank and the hot tank (I don't mean depth of water, I mean height of the water above ground level) is the water in the large tank higher than the small tank?

    Does the water in the small tank seem clean and clear (apart from any brown sediment in the bottom)?

    I understand you have seen the small tank overflowing; have you seen the large tank overflowing?

    how long has it been doing this?

    How many mixer taps (sink, shower, bidet) have you got, and are they fed with mains-water pressure cold supply? Do they have service valves enabling you to cut off water supply to the mixer for servicing?
     
  3. clion

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    Over flow from the boiler will cause the tank to fill. Check the pump is not over pumpimg? and/or that the thermostat is working.If the system overheats then it blows off some hot water and sucks in cold, thus relieving the temperature.
     
  4. clion

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    Sorry didn't read the whole post. The small tank is the central heating expansion tank.So if that is filling the problem is as before.
     
  5. hi-spec plumbing heating

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    check you heating f/e tank vent when boiler is running to see if it's pumping over hot water.

    1, boiler stat faulty. see if boiler shuts down when stat turned down. if so not faulty stat.

    2, pump speed not a problem as you said it's only just started doing it.

    3, most common reason blockage in pipework, check tank for sludge in bottom. most blocks will occur where tank feed joins main system pipework.
     
  6. JohnD

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    If Y5Stu ever replies with information requested (no sign yet) my money's on leaking coil.

    In Hants they like mains pressure on the cold taps even when hot is from a tank, but mixer letting buy would not affect the F&E.

    Note that he says "I took several bucket loads of water out of of the small tank as it was overflowing and went away for the weekend, the central heating and hot water were on via the timer. On our return the small tank was full again, well over the ball cock and water coming out of the overflow."

    All this water is coming from somewhere.
     
  7. gasanova

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    Hi
    Your microversion or coil inside the cylinder is perforated and the water level in the tanks (loft) is equalising and the lowest tank would then overflow. Sort it or your rads will corrode from inside (DO NOT use anti-corrosion inhibiter until its rectified).
    Hot water storage tank ball-valve, change it, the level creeps up over a long period, don't read too mutch into it.
     
  8. Softus

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    It isn't.

    It isn't.

    It isn't.

    See JohnD's post.
     
  9. Y5Stu

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    Thank you for all the replies, I'll try and answer the questions raised to help me sort this problem...

    There are no sign's of leaking around connectors etc.

    The two tanks sit on a platform in the loft with the water level in the large tank being higher than that of the small.

    Water in the small tank is clean other than sediment at the bottom.

    I believe that the large tank does overflow if we are not in the house for a couple of days.

    This has been going on for a few months.

    We have mixer taps in the kitchen (mains fed), bathroom basin (mains fed I think) gravity shower (tank fed). Only the bathroom basin and cold on the kitchen have service valves.

    Boiler starts and stops when stat is turned.

    Pump is not heard to be overrunning.

    Again, thanks for all your help, much appreciated, where do you think the problem lies?

    Cheers Y5Stu
     
  10. Y5Stu

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    Forgot to mention...This may be coincidence but a few months ago whilst showering in nice warm water we would get a few seconds of cold and then warm again. To my knowledge this has not happened for a few months.

    Could this be linked to the other problems being discussed?

    Y5Stu
     
  11. JohnD

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    Sorry to say this clinches it.

    Water is getting from the big tank into the little one

    This is because the coil in the hot-water cylinder has a leak in it.

    You will find, if you go into the loft on a day when the small tank is overflowing, that if you shut off the supply to the large tank, the small one will continue to overflow and the water level in the large tank will drop. When the height of water in the large tank drops to the height of the overflow in the small tank, it will stop overflowing.

    This means you need a new hot water cylinder.

    Once the new cylinder has been fitted you need to give the radiators and boiler a chemical clean and flush, as the flow of fresh water will have encouraged the rads to rust from the inside, and refill with inhibitor. For an extra £100 or so you can have a magnaclean fitted, which will capture the remaining sediment as it turns black over time and is a very worthwhile addition. If not cleaned out, the "rust" sediment is liable to cause blockages as it turns black, especially in your boiler, which can damage it.

    Depending on how long this has been going on for, some of the radiators are at risk of rusting through and starting to leak

    sorry.

    p.s. there might, or might not, be a separate problem with the level in the cold water tank, but this wil be masked by your (more severe) problem with the cylinder. Unless you can verify by observation that the ball cock in the big tank is not dripping, you can fit a new ball cock (this is easy and cheap) and then wait until your cylinder is replaced before investigating further. When this time comes it will be easier to investigate if you have got service valves fitted on the supply pipes to all your mixer taps, as one of them may have an internal leak.
     
  12. Y5Stu

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    Thanks JohnD, one final thing to confirm the hot-water cylinder is at fault...When the boiler is running the overflow rate of the small tank increases due to the water level rising, as it happens when the boiler is operational is this a sure sign that the cylinder is faulty?

    Any ideas on how much I can expect to pay to get a new cylinder fitted and the system cleaned?

    Cheers Y5Stu
     
  13. Softus

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    Not bad, John, but this bit isn't quite right:

    Brown rust (mainly Fe2O3) doesn't turn into black magnetite (Fe3O4) - they are formed by two different electrolytic/oxydising reactions.

    Also, radiator leaks tend to happen when the rust forms at a seam and forces it apart, not by the metal actually rusting through. ;)
     
  14. JohnD

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    :confused: that's funny - I'd heard the brown turned black over time.

    And the brown is hardly attracted to a magnet so a Magnaclean won't get it out. For some reason Brown seems to accumulate in the F&E, do you know why that is?
     
  15. JohnD

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    Y5Stu - sorry don't know current costs, I am just a householder. Best thing is to ask around local friends and neighbours to see who has had some plumbing work done in the last couple of years, and thinks their plumber does a good job, then ask him to take a look and give you a price. You do not need a Corgi boiler engineer for this.

    I think it's like a half-day's work to change the cylinder, not a half-hour job. can be more if pipework is bad or needs changing. when I had mine changed I had a bigger cylinder put in, the old one was a bit small for a big bath. the cylinder might cost about £200, and you will want a new immersion heater fitted, say £20, and various sundries, as well as the plumbers time

    Cleaning you can do yourself with chemicals, after putting it in and getting it circulating for a week, you might spend a day pottering round draining and flushing. If you pay someone they will usually use a Powerflush machine that pumps the cleaning chemical round with great force and dislodges a lot of sediment, this usually costs several hundred pounds.

    I had a powerflush done when I had my cylinder replaced, the guy came in one day to do the cylinder and another day to do the powerflush. Worked out fairly expensive but at the time business was quite good so I didn't mind (much).

    My mother's system was rather sludgy, I cleaned that out myself with chemicals and fitted a Magnaclean which I think is very worthwhile, probably cost me £100 or so in parts and a couple of Sunday afternoons. I did it during the summer, the heating has been on mornings and evenings recently and I got about a teaspoonful more black sediment off the magnet when I checked it last weekend. I previously checked it a month ago.

    I am no plumber but am reasonably sensible ;)
     

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