Vented Cylinder, no Tap Isolation Valves

[RealPolitik]

I need to change an upstairs bathroom tap which doesn’t have any isolation valves at the moment. The cold supply is direct from the mains, for which there is an electric cut-off valve - if I can turn off the fill valve from the cold water feed tank to vented tank, will the lack of flow mean that I won’t need to empty the entire contents of the hot water tank, but just drain the pipework?

 

[gas112]

Nope you will still have the head of water just turn cold off and run the water till taps stop running

 

[RealPolitik]

Thanks, as I thought

 

[Madrab]

You would normally have an isolation valve on the cold feed pipe in between the Cold Water Cistern (CWSC) and the hot water cylinder, usually in the same cupboard where the HW cylinder is located on the pipe and runs into the bottom of the cylinder, may have a red handle and looks similar to this.

 

[Harry Bloomfield]

If you can reach down into the loft tank, and fit a bung, into the top of the pipe which goes down to feed into the cylinder, it should stop the flow. Run a hot tap in the kitchen, to drain the pipes, down, leaving it open, to cope with any leakage past the bung.

Alternatively - tie up the float valve, to stop the tank refilling, then turn hot taps on, until the stop running, but it will waste any hot water you have stored.

 

[gas112]

You would normally have an isolation valve on the cold feed pipe in between the Cold Water Cistern (CWSC) and the hot water cylinder, usually in the same cupboard where the HW cylinder is located on the pipe and runs into the bottom of the cylinder, may have a red handle and looks similar to this.

View attachment 407299

which as all pro`s know have a habit of snapping in the off position causing the diyer more problems and for the sake of a few pennies worth of pre heated water not worth any possible hassle

 

[RealPolitik]

The usual red tap does feel very like it’s about to shear off. To clarify - if I turn off the red valve between cold cistern tank and hot cylinder, will the full contents of the hot cylinder drain when a hot tap is left open (both tanks are at attic level)?

 

[gas112]

The usual red tap does feel very like it’s about to shear off. To clarify - if I turn off the red valve between cold cistern tank and hot cylinder, will the full contents of the hot cylinder drain when a hot tap is left open (both tanks are at attic level)?

no it will just empty the pipework but if it snaps in off the position you then have 25 + gallons of water stuck above it with the additional hassle of changing that valve which in some instances is not straight forward

 

[denso13]

To clarify - if I turn off the red valve between cold cistern tank and hot cylinder, will the full contents of the hot cylinder drain when a hot tap is left open (both tanks are at attic level)?

Nothing should come out of the taps, maybe a dribble. It is the loft cistern that would empty though, not the cylinder.

 

[Harry Bloomfield]

The usual red tap does feel very like it’s about to shear off. To clarify - if I turn off the red valve between cold cistern tank and hot cylinder, will the full contents of the hot cylinder drain when a hot tap is left open (both tanks are at attic level)?

No. The water will only flow out, until it reaches the top of the cylinder, then stop.

 

[Madrab]

If the red gate valve has been tried and it feels tight or isn't running smoothly then it's probably time to replace it as there should always be a functioning method to isolate the cistern from the cylinder so the amount of wasted water hot or cold is minimised.

If the valve is dodgy then you can bung the cistern and both the tap feed could get an ISO valve fitted and the gate valve replaced to a lever valve for all future HW work requirement, draining down anything up to 50gals (cistern size dependent), is just a complete waste of water IMO.

 

[Madrab]

Of course, how straightforward it will be depends on how handy a DIY'er you are but it is very doable if you're handy.