Isolating hot water supply.

[amfisted]

Spoon feeding time again.

In our previous house we had a combi, and turning off both hot and cold supplies was a doddle. Here we have a gravity fed hot water supply, and the gate valve from the loft storage tank to the hot water cylinder is stuck fast. The only other time I needed to work on the hot water system, I went for the option of a pipe freezing kit, but it only last a few minutes and barely gave me time to get the job of fitting new bathroom taps done.

This time I'm replacing a monobloc kitchen tap and the 300mm tails are far too long for the existing pipework, so I need to shut off both hot and cold and shorten the supply pipes. Am I correct in thinking that if I turn off mains water and run the hot tap to empty the loft storage tank, then eventually the hot taps will lose all pressure? Is there any safety aspect to be observed when doing this?

Many thanks.

 

[wundaboy]

That all sounds fine. Just make sure the boiler/immersion heater or whatever heats the hot water cylinder is turned off before you start work.
If your current gate valve is seized, take the opportunity to fit one of these in its place for ease of future maintenance.

Also, seeing as you're cutting the pipework, you could fit isolating valves on the feeds to the kitchen sink also for future maintenance.

 

[bernardgreen]

Alternatively you might be able to plug the end of the pipe in the cold water tank with a mushroom.

Wooden dowel that is a loose fit in the pipe and a disc of soft rubber or flexible plastic. When the tap is turned on the water pressure will press the disc against the wall of the tank.

 

[amfisted]

Many thanks for the replies. I might replace the gate valve in the future, but my current focus is to get the kitchen taps working before 'er indoors gets sick of washing dishes in the bath and goes for my throat. So I'll concentrate on that for now via the quickest route. I read somewhere else about bunging the cold water tank, but it sounds potentially fiddly so I'll go for emptying the tank via the hot taps. Its a 20 gal tank so I suppose will take about 15/20 minutes to empty.

I will fit isolators, because although there is already one on the hot kitchen supply, as I said earlier the pipes are too long for the tap tails so everything needs to be moved down six inches. There doesn't appear to be an available tap tail length of less than 300mm, otherwise I'd simply change the tails.

Thanks again.

 

[Madrab]

Careful, if you empty the cold water cistern in the loft trying to drain the hot water cylinder you could introduce air locks into the pipework.

Ideally you do want to bung the outlet in the cistern and open the hot water taps till it stops running. Change the red wheeled gate vale for a lever ball valve, you know you want too

You don't need anything smaller re the tap tail, just pig tail the pipe. Not too tight a circle

 

[amfisted]

Thanks for the warning. I think I’ve got away with emptying the tank without creating airlocks, but obviously the best long term solution is to replace that valve,and I’ll be sure to do it soon rather than waste another 20 gals next time I need to shut off the hot water. Isolators are fitted on both hot and cold now, but the sink waste has defeated me till tomorrow because some fool has angled the outflow pipe upwards. Off to Sfix again in the morning.