Emptying water supply after water turned off

Discussion in 'Plumbers' Talk' started by Richard Bronson, Nov 10, 2018.

  1. Richard Bronson

    Richard Bronson New Member

    Hi all

    Need to remove a radiator. Have turned off water supply outside. Water supply/pressure has dropped inside house but still water coming out. How long do I have to wait. Have waited 30 mins. Water still coming out. Any ideas? Also if there is no water coming out of taps upstairs does this mean I can remove radiators upstairs without threat of flooding upstairs I.e is upstairs effectively ‘isolated’?

    Sorry for the rambling:) Any help would be great!

  2. Dam0n

    Dam0n Active Member

    In a word no. The ch system and hot+cold water will be separate.

    Do you know if you have a pressurised or gravity central heating setup?

    To replace a radiators you need to drain down the system to the level of the radiator you want to change out. There are ways to do it without draining but probably beyond scope of this thread.

    Look for a drain cock on the bottom of the radiator this will be where you drain the system from. Open a bleed valve on the highest radiator in the house. Even with a f&e tank It'll still help. Just make sure you close it off afterwards.

    Assuming you have a gravity setup. Leave the mains tap off whilst you do this.
  3. Allsorts

    Allsorts Well-Known Member

    Hi Richard.

    I'm assuming you have a vented system, which means you have a couple of black plastic storage tanks in the loft?

    If so, the smaller of these tanks is for the radiators (and boiler) (called the F&E tank) and the larger one is your cold water storage (CWS) tank which provides cold water to most of your cold taps and hot water via your hot cylinder) to your hot taps.

    They are separate. So if you've been running a cold tap in order to drain your radiator system, you have just wasted quite a lot of water...

    You usually don't even have to turn off the whole house's mains water in order to drain a rad - which is good news as these 'simple' jobs often go pear-shaped especially at the weekend (what day is it?) and end up taking much longer than you hoped.

    Ok, if you DO have two tanks in the loft, I think it's time to familiarise yourself with them. Go upi there with a good light or torch, don't go through the roof, locate the tanks and look at them.

    ID the smaller one. Look at the copper pipe which goes in through the side near to top - inside the tank you should hopefully find that this goes to a ballcock? Ok, on the supplying pipe see if you can find an isolating valve, something that can be shut off using using either a screwdriver (quarter-turn) or even by hand. Is there one? If not, another solution is to place a stick across the top of the tank and tie the ballcock arm up securely using some string.

    Once you've shut off the supply to that SMALL tank, the rest of the house can still have water. You then drain the RAD system (and that small tank will also empty) until you are confident that the rad you wish to remove is empty (tho' it'll still contain some water, and this will likely be black and horrible and very stainy of carpets - so take care).

    To drain your rad system, see if there's a drain cock on it somewhere - it should have a nozzle to fit a hose over. If you don't have this, then I guess the best way to drain your system is to choose the rad you want to remove, FULLY shut off the valve at each end, slowly slacken off one valve-to-rad connection, and allow it to drain - controlled - in to a low pan or tray. Don't fully pull away the valve - leave it 'on' the rad so ready to redo it to stop the flow whilst the pan is emptied.

    If you undo the rad's bleed screw, this will increase the draining speed - but be in control.

    Once the rad is empty, you can then remove it and leave the closed valves in place which will prevent you having to drain down the whole system - you can even run your CH system.

    Why do you need to remove the rad? Are you planning to replace it afterwards? If it's permanent, then you will have to fully drain down your system so's you can cut and cap-off these pipes presumably under the floor.

    To fully drain the system, open a valve...

    Any other rad on the system you don't want to empty, then shut them off at BOTH ends first - they'll remain full of water. NB - on the lockshield valve, you MUST count EXACTLY how many turns and part-turns each takes to shut off, write this down and leave it near the rad. When you are done with your work, open these the EXACT same amount.
    Richard Bronson likes this.
  4. retiredsparks

    retiredsparks Well-Known Member

    Or... you could just isolate the valves both ends of the rad..bleed off the dirty water from rad(by loosening one valve) remove and ...change rad.
    No need to drain the system..or turn off anything (apart from the boiler)
  5. Allsorts

    Allsorts Well-Known Member


    And I don't mean Br**** for once... :rolleyes:
  6. DIYDave.

    DIYDave. Well-Known Member

    9” paint roller trays are great to collect water from draining down a rad in situ

    Put down old towels to collect any spillages then butt up roller tray under valves tight to skirt

    The roller trays from say 99p land aren’t too good as so flimsy, once heavy with water there’s a disaster waiting to happen when you then go to pick up tray :eek:

    Also don’t understand the detail
    of the above answers. If your simply temporarily removing rad, then refitting it say during decorating, just shut off both valves, drain and then whip off

    Can fit blanking caps to valves for extra water tight security
    retiredsparks likes this.

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