Isolate hot water in unvented pressurised system

[Hillabaloo]

Hi,

I need to turn off hot water in bathroom. There are no isolation valves from unvented indirect pressurised tank in loft. Turning off mains to house stops hot and cold water upstairs, but the hot in kitchen still continues to run (but at reduced pressure). But when I turn mains back on there is a lot of air in system. I thought turning mains off should stop hot as well, but it appears that it will drain hot water tank if I have kitchen tap on. Is this right? The house is three storeys, so alot of head pressure - is this the cause?

My work is on top floor,where the flow stops so seems to be OK, but as I to need to cut into the bath's 22 mm hot supply pipe I'd rather no cockup.

Be very grateful for any advice.

 

[Ben-gee]

Yes isolate mains going into cylinder, there should be a shut off valve just before or incorporated into the cold water combination valve...
If not just turn off main stopcock as you did.

Hot water will continue to flow until the pressure in the cylinder is reduced, then it will stop - could be a fair bit.

Always a good idea to have a tap open on the floor below where you are working to allow the pipe work to drain fully.

You’ll be fine.

 

[Hillabaloo]

Yes isolate mains going into cylinder, there should be a shut off valve just before or incorporated into the cold water combination valve...
If not just turn off main stopcock as you did.

Hot water will continue to flow until the pressure in the cylinder is reduced, then it will stop - could be a fair bit.

Always a good idea to have a tap open on the floor below where you are working to allow the pipe work to drain fully.

You’ll be fine.

Thanks Ben-gee. Job scheduled for Monday.

 

[ShaunCorbs]

turn the mains water off open cold tap in the kitchen then open one upstairs wait for it to stop close both

open kitchen hot tap and then open a hot tap upstairs will take around 5-10 mins to stop fully

 

[Hillabaloo]

turn the mains water off open cold tap in the kitchen then open one upstairs wait for it to stop close both

open kitchen hot tap and then open a hot tap upstairs will take around 5-10 mins to stop fully

Hi Shaun,

Thanks for that. Will this drain the hot water cylinder?

What should the sequence be when turning water on or doesnt it matter?

 

[ShaunCorbs]

Hi Shaun,

Thanks for that. Will this drain the hot water cylinder?

What should the sequence be when turning water on or doesnt it matter?

no not totally will drain prob around4-6” off the top

no but I would do the cold taps first close to stop tap then upstairs runn until it stops spluttering bath is best then repeat for hot

 

[JCplumb]

I don't have an unvented ticket, but to me that's going to be the situation that has previously seen unvented cylinders implode, or at least cave in. If it's not could someone enlighten me as to how people have managed to make these type of cylinders implode?

 

[spanner]

Brilliantly suggested as apposed to the cylinder being on upper tier of the house would open an upper tap as well as the lowest. and individual if on arrival full on hot water