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DIYer, changing two TRVs on rads, is too risky for someone with little experience

Discussion in 'Plumbing and Central Heating' started by robpeake, 22 Sep 2021.

  1. robpeake

    robpeake

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    evening all i have conventional vented boiler system with header tank in the loft.
    Last winter i had two TRV's which are leaking quite badly and i tried using some ptfe tape and no luck.

    So i've done a fair bit of diy around the house, such as fitting new doors, staircase and i've done some work on car interiors and electrics

    three methods i've seen to do this, i've been watching a few videos and I really want to be able to do this but i'm now finding myself bottling it thinking i can get myself in a right state.

    three methods i've watched

    freezing the pipe with a spray can kit and swapping the valve out - doesn't seem popular or it doesn't seem to work very often and when it does it lasts about 5mins and i will need longer

    using the rubber bungs on the vent and cold feed in the header tank and then swapping out the valves, saves draining down the whole system- bungs sometimes fail and i read somewhere depending on the cold feed outlet some of the bungs don't seal completely do to the outlet

    and lastly a complete drain of the system, i have a drain valve near the backdoor on the little rad and i have a couple more bottles of brand new inhibitor but im worried after reading a few stories that you can get air locks and its sometimes really difficult to clear them from the system so its kind of putting me off

    The draining the system seems the most sensible but i really worried about causing myself some real problems that i then cant fix, the bungs i wont know if they worked (will I) until they are in and the valve im changing is leaking.


    what you recommended method the diyer attempts to do this?

    thanks
     
  2. oldbuffer

    oldbuffer

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    1. You could hire an electric freezer. Provided you don't get a power cut these will freeze for as long as you want. If you go this route:
    1a. Freeze the pipe as far from the valve as you can.
    1b. Once frozen and you have undone the joint, clear water from the freeze head to the open end of the pipe. Otherwise that water will freeze and make it difficult to get the valve on.
    1c. Wear good gloves while handling the frozen freeze heads. I didn't on one occasion, and got (very mild) frost bite.

    2. I personally don't think the bung method is suitable unless you have the experience to deal with a sudden release of water in the event the bung fails.

    3. Draining down is the safest and cheapest option. But if you are going that way:
    3a. Empty the Feed and Expansion (F&E) by bucket. Don't drain it down via the system, or you will wash any muck in it into your pipes, radiators and boiler.
    3b. When you have it empty, give the F&E a good clean.
    3c. See how quickly it drains. If it is very slow / only dribbles out, you may have a blocked feed. If so, sort it out while the system is empty. A decent feed also reduces the chance of airlocks.
    3d. Re-fill with water only and run the system. That way, if you have leaks you can drain again and fix them without wasting £15 worth of inhibitor.
    3e. If, when you have finished, you are going to add inhibitor via the F&E, drain down enough to empty the F&E plus a bucket of water. That way, you can pour the inhibitor into the F&E tank and it will get washed straight into the system when you refill. If you add it to a full F&E it may never get into the system.
     
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  4. Lower

    Lower

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    Close off all the valves on the radiators (making a note of how many turns it takes to close the lockshield valves) and then drain the whole system.

    Airlocks are rarely difficult to clear on a heating system in my experience.
     
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  5. jeff the gasman

    jeff the gasman

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    Give yourself a break and get someone to do it for you.
    It’ll cost 10 times more if it all goes wrong.
    You need a good basic knowledge of how to get out of any problems as and when they occur.
    Ask @Harry Bloomfield ! He’s had a first hand experience recently.
     
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