Prevent Outside Tap Feed Freezing

[Rtplumb]

Thanks for the reply. I contacted the Plummer and the tap does include a check valve. I have asked him to come back and fit a drain valve at the lowest point in the pipework.

The justification for leaving the tap open in winter is odd. The amount of expansion (10%) when water freezes would surely make little difference to air pressure in the empty section of the pipe - although a little of course provided the tap provides an effective air seal (which I doubt).

Getting a drain off fitted to the external tap pipework is a good idea.

When an outside tap is closed the water in the pipe is still there, all the way to the tap washer (if not drained) leaving no room for expansion. As you know, water doesn’t compress, so something will have give if water in a sealed pipe freezes.

Now, I don’t know everything there is to know about plumbing and heating as I’ve only been doing domestic, commercial and industrial plumbing, unvented systems and heating for fifty years, but I do know the physics behind water expansion in a sealed system, be it frozen through to steam.

Hope you find this useful.

 

[SimonG]

Thanks for the reply. I contacted the Plummer and the tap does include a check valve. I have asked him to come back and fit a drain valve at the lowest point in the pipework.

The justification for leaving the tap open in winter is odd. The amount of expansion (10%) when water freezes would surely make little difference to air pressure in the empty section of the pipe - although a little of course provided the tap provides an effective air seal (which I doubt).

For new installations tap with built in check valves is non compliant. Only to be used in like for like replacements.

 

[Traveller 47]

For new installations tap with built in check valves is non compliant. Only to be used in like for like replacements.

Thanks, I didn’t know that - and presumably my plumber doesn’t either!

My point about the expansion of water with freezing was that, in my case, about 12 inches of the pipe was drained and about 24 inches was not. I consequently though there would be plenty of room for expansion even though the tap was closed. Obviously I was wrong because the pipe shifted a little in the compression joint on the downstream end of the isolation valve.

 

[Traveller 47]

Thanks, I didn’t know that - and presumably my plumber doesn’t either!

My point about the expansion of water with freezing was that, in my case, about 12 inches of the pipe was drained and about 24 inches was not. I consequently though there would be plenty of room for expansion even though the tap was closed. Obviously I was wrong because the pipe shifted a little in the compression joint on the downstream end of the isolation valve.

I am interested in the comment above that outside taps incorporating check valves are now non-compliant in new installations. Where can I find the regs stating this? I want to show my plumber.

 

[ShaunCorbs]

https://www.hurlstoneassociates.co.uk/files/HA%20Arrow%20Valves%20Tutorial%202.pdf

 

[Traveller 47]

https://www.hurlstoneassociates.co.uk/files/HA%20Arrow%20Valves%20Tutorial%202.pdf

Thank you!