IS MY HOT WATER SUPPLY AIRLOCKED

[RASH]

I turned off mains water while I was away over the weekend due to a leaky hot water tap. On my return I find there is no hot water coming through although cold water supply is normal.The cold water tank is in the loft and hot water cylinder (with lots of hot water) is on the ground floor.
Is there an airlock somewhere if so how do I resolve it.

 

[croydoncorgi]

Assuming you have a conventional system, with a cold water tank in the loft (ie. NOT an unvented hot water system), you could easily have airlocked the thing by turning off the mains water supply.

You say you turned it off because of a leaking hot tap: was the leak bad enough so that over the weekend the cold tank would have emptied via the leak? Is the leak now fixed?

If yes to both, proceed as follows:
- check that there's water in the cold tank. If not, check that the float arm (the thing with the ball on the end) is not stuck in the up position. If no water flows into the tank, ther's a problem on the 'rising main', where the mains water comes in. It's quite unlikely that the rising main is airlocked (although not impossible), so are you sure you turned on the water fully?

- if there is water in the cold tank, do the COLD taps fed by it (eg. the cold tap on the bath) work properly? Probabably yes, otherwise come back here!

- so, having proved that ONLY the hot taps are not working.....
if you have a hand-shower attached to the bath taps, unscrew the handset from the end of the hose (do not lose the rubber washer), put your thumb over the end, turn on BOTH hot and cold taps and operate the shower button / handle. Wait for 30 seconds of so, then turn OFF the COLD tap and remove your thumb. With luck, hot water will now run out of the end of the hose. If so, reassemble the shower handset and problem solved.

- If not, try the same trick with the mixer tap on the kitchen sink. This is trickier, because you've got to arrange things so that water flows out of the cold and back into the hot side of the spout (there are usually TWO separate pipes inside the spout. I usually use an old rubber glove or similar doubled over the end of the spout so that there's enough room left for water to circulate. Be CAREFUL. At the kitchen sink you will be putting cold water at mains pressure straight into the hot supply. It will flow back into the loft tank and if you leave it running for too long the cold tank will overflow.

 

[Gary_M]

I have heard of one way of resolving an airlock - but have never tried it, so not sure how effective it is - basically, you connect a hose from the cold tap to the hot one, open the hot tap first, then the cold - the pressure from the cold tap is supposed to push the airlock up the hot water pipe.

My thoughts are: be careful not to put too much cold water up there in case it goes in faster than your overfolw can get rid off


PS I must have been writing this at the same time as croydoncorgi Didn't mean to steal your limelight

 

[RASH]

Thanks for the advice it's done the trick. Not sure whether the airlock was unlocked or the ice was deiced. Now we don't need the kettle as much!