Any Hot Water Tank Experts?

Discussion in 'General Chat' started by Fatti, Sep 17, 2007.

  1. Fatti

    Fatti
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    My wife has decided that as part of some up and coming decorating tasks, we need some taps changing in our en-suite bathroom. For the hot water we have the bog standard copper cylinder up stairs fed by a tank in the loft - the indirect cylinder according to this. It would seem therefore, that to change the cold water tap is pretty straight forward - just turn off the main feed into the house. For the hot water, I've got to turn off the feed from the tank in the loft to the copper cylinder (no problem, there is a stop tap in the way), then turn on the hot taps to drain the whole tank....which seems a bit of a waste.

    From the link, why don't they put an stop tap a position 7 so the hot taps can be isolated from the tank? If ever a hot water pipe bursts, the only way to stop the water would be to turn off the cold water supply to the cylinder and wait for the copper cylinder to empty into the house.

    The article also states that the heat exchanger in the cylinder is a run from the central heating and it's water heating capabilities are a secondary function of heating the radiators. If this is the case, why, when the heating is off, and the hot water on the timer is turned on, don't the radiators heat up?
     
  2. Sporran

    Sporran
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    Most central heating systems have 2 seperate circuits, one for hot water and one for rads. They usually have a computer controlled valve system which can feed hot water to either or both circuits at the same time. This allows just radiator heating or just hot water/cylinder heating.

    As for stop cocks from the installs i have seen there end up anywhere and everywhere, we have one exactly at location 7 :) and others along the lines.

    Stick your head in the Airing Cupboard and have a good look around :)
     
  3. Fatti

    Fatti
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    Thanks Sporran, the tank sits on a shelf about 18" up and the area underneath has a screwed on cover. I will undo that tomorrow and have a look to see if there a stop cock hidden behind that.:)
     
  4. RichardK

    RichardK
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    As you say having to drain the tank is wasteful, and I believe that is why current regulations (and I think its been the case for a number of years) require individual isolation valves for each tap, so you may find one on the pipe next to the tap.
     
  5. anna the dub

    anna the dub
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    I would be very surprised if there is not a gate valve located very close to the cylinder on the hot feed to the taps. I have seen many of these type of heating systems over the years and have never seen one without an isolation gate valve somewhere between the cylinder and the taps.
     
  6. IronGiant

    IronGiant
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    The system in my house has no isolation valves between cylinder and taps :) When I put my new bathroom sink in I will remedy that, but I will need to drain the cylinder in order to do so. The system has a few even more interesting quirks as well :D

    Dave
     
  7. T0MAT01

    T0MAT01
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    The gate valve is normally on the cold supply into the hot tank, since if no water can enter the tank then no water can exit.

    If a gate valve was above the tank and turned off then the tank wouldn't be able to vent and it would build up pressure.
     
  8. Fatti

    Fatti
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    I certainly can't see a valve on the output side of ours either, and there are no isolating valves on each of the individual supplies to the taps, which I thought was surprising since the house is only eleven years old. I think I might get a handful from Screwfix and add them in as I go round. I work with someone who's husband is a gas fitter so she is going to ask him if there is any reason I can't put a valve on the boiler output.

    There is an isolating valve on the cold water supply into the cylinder from the loft tank. From the article in my first post, and what T0MAT01 has written, I would have thought the same - no water in, no water out. I've just turned this valve off and run one of the hot taps, and it's still coming out. I popped the loft hatch and I can't hear the tank filling so I assume the valve is OK. The tank is warm but as there is the vent pipe going back into the loft, I wouldn't of thought it would be coming out under pressure:confused:
     
  9. T0MAT01

    T0MAT01
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    I wouldn't do that, it'll just restrict the flow.


    If the water in the loft tank was hot then you're probably looking in the central heating feed and expansion tank rather than the (bigger) cold water storage tank.

    How much water came out of the hot tap with the gate valve turned off? (how long did you let it run?).
    There will still be water in the pipework from the top of the hot tank to the tap which needs to empty first, then it will run dry and glug - although it's not unknown for a gate valve to fail.
     
  10. Sporran

    Sporran
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    ello fatti,

    think im misreading you but if im right, even if you isolate the cold feed in to the tank, the water still still run until empty due to gravity, water weights quit a bit hence why cylinders tend to be upstairs and feed tanks above them or in the attic. This weight creates static head which forces the hot water out under its own pressure.

    If you are sure you have isolated the feed just run the tap it will take a while but will run dry, that is if, depending on your system you have isolated the feed to the hot water tank and not your central heating expansion tank. The hot water is usually the bigger of the 2, but that aint always the case.
     
  11. Sporran

    Sporran
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    lol Tomato1, just seen the post times :D
     
  12. Ruperts slippers

    Ruperts slippers
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    Usually a gate valve is placed on the cold feed from the tank if you close that ,the gravity effect of cold water filling the cylinder from the bottom and pushing the hot water out of the top cannot happen so when you open your hot tap only the water left in the pipes will drain.

    These type of systems use a port valve either a 2 port or 3 port this controls the hot water and heating ,when the heating is off the water flows from the boiler and goes thru the cylinder and back out and down a second return pipe and then back to the boiler,if they are piped up incorrectly the bathroom radiator gets warm when the hot water is switched on.
     
  13. bobsplace

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    Or piped up correctly.."old style" plumbers used to do this on purpose,normally to a towel rail so they were always warm...Just turn the rail off in the summer when its too hot...
     
  14. IronGiant

    IronGiant
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    My hot water cistern empties completely even if the cold feed is shut off if I open a hot tap and I know the gate valve on the feed works because it only empties a cistern's worth, without triggering the ballcock in the loft tank. And my cistern is six inches off the ground in a Bungalow.

    And I don't have any motorised port valves at all, but it all works perfectly; I told you it was quirky :D


    Dave
     
  15. Uridium

    Uridium
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    Turn the cold feed off to stop tank refilling, have a nice hot bath to use the hot water up. Water isn't wasted then is it :thumbsup:
     
  16. eviljohn2

    eviljohn2
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    Sorry to resurrect the thread but following a major overflow problem last week (don't ask) I'm investigating the plumbing in my (rented) flat.

    I have a valve on the mains into my flat.
    A tap out of this to the electric shower with a valve on it.
    Direct feeds to the cold water tank and the kitchen tap.

    Simple so far.

    I have a gate valve on the output from the cold water tank which feeds the toilet and bathroom taps.

    I have another feed from the cold water tank going to my boiler with a gate valve on it.
    This gate valve just seems to spin continuously in either direction unlike the other one which screws in and out to shut/open the system. Why would this valve just spin? I assume it's broken but is there any to tell without completely draining my system bit by bit to find what's going on? :)
     

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