possible air lock?

Last week I turned off the water to upstairs taps as I wanted to replace bathroom handbasin taps. When I turned off the water I think that the toilet had been flushed and was only half filled up. When I turned the water bk on everything seemed grand until someone flushed the toilet. Now when the toilet is flushed there is a small thud in the attic the cistern fills up to half full then it slows to a trickle theres a 'water hammer' sound then the water comes bk stronger and the cistern fills up. The noise was extremely loud the first day but doesnt seem as loud now. Still very annoying when people come in late at nite I have tried ..................

1. Squeeze the single mixer tap outlet so that the palm of your hand covers it firmly
2. Turn on the hot, then the cold, (this order is important to prevent confined mains pressure from forcing your hand away from the tap outlet). The cold supply, now unable to exit from the hand blocked tap outlet, will instead flow across to the hot water pipe causing a backflow in the hot water system, clearing the airlock

Note: If you have a similarly non-mains pressured COLD supply i.e. also fed from a header tank and which also has an airlock: Same as just described but this time you need to use the mains pressured water to purge the non-mains pressured COLD
supply, which, unlike the hot supply, is probably inaccessible from downstairs and therefore nowhere near any mains pressured water.

1. Unscrew the showerhead from the pipe
2. Place 2 or 3 layers of plastic bag over the end of the pipe to form a strong membrane
3. Re-screw the shower head with the membrane still in place
4. Go to the header tank and turn ONLY the hot outlet OFF. Leave the cold one ON
5. Go back to the shower taps and turn both hot and cold ON, with the diverter in the SHOWER position
6. Go back downstairs and carry out the procedure initially described i.e. using hand pressure over the mixer taps

The mains pressured water will now back flow up into the hot water system but then; flow across to the non-mains pressured cold water system via plastic bag blocked; mixer in the bathroom thus clearing any air locks in the non-mains pressured cold supply.....................................



which i found on this site. Only tried it for few mins as i was afraid i might do more damage. Any help please

It sounds like your problem may be with a non-mains supplied cold-water supply to your toilet. A simpler procedure if you've got a length of hose and the right adapters for the taps is to connect the kitchen cold tap to another tap off the same feed as the toilet and then blow out the airlock.

I don't see what damage you could do. Try it again.

Water hammer happens on high pressure supply only.

Does hammer only occur with toilet?

Is your toilet supply mains fed? If so, rip ballcock and clean nossle as it may be partially blocked.

When you turned off water, are you sure you opened mains fed completely?

If water hammer is occuring at storage tank in attic, it may be time to change ballcock. Is DIYer doable.

If the water hammer is from the cistern, then change the ballcock.
I only changed one recently where the shut off pin in the ballcock was moving freely causing the hammer noise.

Ballcock in cistern was only replaced 9months ago and prob only started when i turned off water so im assuming there is a connection. As far as i can c there doesnt seem 2b a problem with ballcock in attic. General Zod .........im no plumber as u hv probably gathered wd u mean connect cold tap in kitchen 2 cold tap in bathroom? Will hv 2 get longer hose but i'll try that. tnks

If that doesn't work just try knocking water off at mains again and emptying the whole system.
Before re-filling, leave all taps open a small bit so any air in the system can be expelled...always worked for me if there was an airlock.

Tnks Bren. When I turned off water originally it was in hot press so I wd need to turn it off at kitchen sink? Sounds like it wd be easier than joining hoses. Will try that tnks again

many months later and nearly demented with the noise thought id let u know the problem is solved. maybe not very technical but i turned down the water pressure in the hot press and the noise stopped. we dont hv great pressure out of the cold taps now but god its good to be rid of the knocking sound. Jus u are probably right but i didnt really understand at the time. we had only recently replaced the ballcock so i thought it shd be fine. it was difficult to get at the time as it needs 2b at an angle because of the shape of the syphon..........I need a new bathroom!!!!!!!!!!