Overflow from Expansion Tank

Discussion in 'Plumbing and Central Heating' started by DaveB511, 6 Jun 2004.

This topic originated from the How to page called Plumbing in a cistern.

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  1. DaveB511

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    Hi - the Overflow from the Expansion tank has recently started spewing hot water into the garden, at periodic intervals.
    On investigating, the vent pipe from the hot-water cylinder is the culprit, with spurts of water topping the expansion tank up.
    Any suggestions? Those that spring to my mind are:
    (a) thermostat has gone
    (b) hot water tank contains too much water initially
    (both cases on the assumption there is too much water, so the excess is being fired out through the vent pipe)
    Appreciate any advice on most likely cause, and possible solution
    Tks
     
  2. masona

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    Could be water expansion causes by overheating, I has this with mine and found the boiler stat was full of dusts, cleaned it out and now okay but turn off the mains first or could be the boiler stat setting is too high or faulty , try and turn the setting down and see what happen. You may have a sludge build-up which restricted the water flow back pressuring the F&E tank..
    See what the others think
     
  3. oilman

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    I think you should tell us something about your heating system, (see the post at the top of the forum). You haven't said what provides the heat, it could be a coal fired Parkray or an electric immersion heater, or perhaps it's not.
     
  4. DaveB511

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    Apologies for not providing enough detail (I came to the forum from a Search, so didn't see the 'advice' posts initially).

    Right - boiler is gas-fired GlowWorm (prob about 20 yrs old)
    It's a 2-circuit system (cold-water and expansion tank in the loft)

    No work has been done to it recently - only related work was earlier this year when i had thermostatic valves added to the rads.

    Problem started late Friday, and happened again last night - both times at arund 9PM

    One other thing - looking at the boiler itself this AM, the stat is set to 180, whereas I normally have it down closer to 140 - not certain when it was changed, and by whom, but shall be looking to find out
     
  5. croydoncorgi

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    Several possible causes for F&E tank overflow:

    In order of probability:

    - if it's 'spurting' from the vent, chances are boiler is boiling (!) because the thermostat's set too high and / or it's failed to cut out on overheat (given your comments, the stat's implicated but I'd check out the boiler's overheat sensor too - also possibility it hasn't got one - CORGI job);

    - if its trickling / running steadily from the vent pipe into the tank, so the tank water gets HOT AND you have a separate cold feed pipe from tank to C/H system, chances are that the cold feed is (partially) blocked. Common problem, requiring a bit of pipe replacement / rodding-out;

    - if there's NOTHING coming out of the vent pipe, the F&E overflows AND the cold water tank level is HIGHER than the normal level in the F&E, possibility that the coil in the hot water cylinder is split / corroded through.
     
  6. DaveB511

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    Thanks for the replies

    To confirm - it was 'spurting', not a steady stream/trickle

    Early indications are that it is indeed the stat on the boiler itself - have put it back down to 140 (from 180), and thus far nothing has come through the vent pipe - will keep an eye on it over the next few days, and will look to the other suggestions if it recurs.

    Thanks again

    Dave
     
  7. ChrisR

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    "Overflow from the Expansion tank has recently started spewing hot water into the garden, at periodic intervals.
    On investigating, the vent pipe from the hot-water cylinder is the culprit, "

    You didn't mean that did you?? :eek: The vent pipe from the hot-water cylinder shouldn't go to the heating f/e tank. ??
     
  8. Vostick

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    I have a similar problem with overflow from the expansion tank though it only overflows at the moment that the central heating is switched off (not the hot water).

    Any ideas?
     
  9. jackscout

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    I have a problem with the heating system .

    System
    Oil fire boiler (typical self contained insulted unit located outside) heating hot water cyclinder and 5 rads all located at ground floor-
    Feed and expansion tank located overhead in attic
    seperate cold water storage tank (both tanks located at the same level in attic)


    The system was recently drained to allow removal (temporally) of a rad (rad was located adajacent to drain valve)

    Problem

    When the heating system is on for a period 15 minutes or longer (time necessary to heat water ) the feed pipe from the supply tank (hot water) gets very hot and fills with water, which backs up into the feed tank, quickly heating all the water within the tank to boiling point and eventually overflows (I fitted an overflow pipe to prevent it overflowing onto the ceiling.) Also there's a lot of steam starting to come from the boiler.
    I have bled the pump, and rads several times and also allowed water run through the system while the drain valve was open before turning on the boiler.

    Any advice much appreciated.
     
  10. chambersn

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    I have recently started having water trickling out of the overflow from the hot water feed expansion tank. I have a 2 year old gas boiler. I originally thought the problem to be the ball valve so I replaced it (about 20 yrs old). The problem still occurred. It happens twice daily typically with the current hot water usage, and can be stopped by running the hot water tank for approx 1 minute. There is an overflow pipe feeding into the tank and I guess it is overfilling from this.

    Is this the Emersion heater tank?
    What can cause this?
    What should I check out?

    :(
     
  11. Bahco

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    Are you saying that your cold water cistern that feeds cylinder is overflowing and trickling outside your house :?: :confused:
    If so check your float valve is set properly. The water should stop refilling the cistern 25mm below the overflow pipe. Bend the metal arm up or down to achieve this (gently with both hands not putting any pressure on the valve).
    If water is entering the cistern from the vent pipe (crooked pipe bent over the cistern suspect cylinder stat is overheating and turn down or replace.
    If water is entering from cylinder feed you have a split coil and need a new cylinder. :cry:
    Attempt first one yourself but would consider calling a plumber/heating engineer for other two :)
     
  12. chambersn

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    Thanks for that! - Bahco.

    I have carried out number 1, suspect 2 or 3, as described.
    I'll let you know of outcome.
     
  13. Steve A

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    I too have water flowing from my vent pipe.

    My configuration is:

    Vented system with a gas boiler (about 15 years old). Was working fine until I fitted a new pump in the bathroom and as a result had to fit a new hot water tank with a surrey flange (to prevent air going to the pump). The expelled water and the water in the loft tank are both luke warm but there is nothing coming from the vent pipe.

    I can stop for short periods it by running off some hot water, otherwise it trickles about 1 pint every 5 10 minutes - onto my flat roofed garage!

    As the hot tank is new (4 days old now) so I do not believe it has a split coil, but I cannot fathom out what else it could be.

    But a side several other taps have started dripping - but I had put that down to the dirt in the pipes following the drain down etc.

    Any clues would be gratefully received.

    Steve A
     
  14. shadow007

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    I have a similar problem. I have an oil-fired boiler heating 5 or 6 radiators and hot water boiler. It is a very old system but I recently had installed a new burner but I think the problem of my f & e tank filling up has existed since before I changed the burner.

    Bothe the F & E tank and main cold water ctank are at same level up in the attic.

    I emptied the F & E tank to be down below the overflow outlet and have bent the ballcock way down to close off new water coming in and there don't seem to be any lvalve leakages. But still the F & E tank has filled right back up again the nex day 3-4 litres, past the overflow pipe and I get a steady drip drip down the side of the house. I notice also that my HW boiler heats only at the top and is not as hot as it should be. Can you please advise.
     
  15. pat6921r

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    OK hare goes recently changed the zone valve as it was gone then the water pump went so i changed the head on that, im still getting water overflowing from tank upstairs in loft so much that the its coming into 1of the rooms I would understand if the heating was on but only the hot water was on,

    I dnt knw wot to do could be thermostat or stat dnt knw wots the difference b4 i changed the zone valve water wld over flow into garden butknw its too much i have bleeded the system check for air etc etc n realesed air from every where

    the system i have is old its a baxi boiler in the kitchen and a cylender tank int he 1st floor plz advise
     
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