Discuss Prevent Outside Tap Feed Freezing in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

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I had an outside tap fitted by a professional plumber last autumn. During the recent cold weather the feed pipe under the kitchen sink froze and the compression joint where the pipe enters an isolation valve now leaks. The outside tap was covered for the winter by an insulating blanket.

I believe the problem is that the feed pipe from the T joint with the cold water riser ((up to the cold water tap in the sink) travels horizontally for about 12 inches before turning vertically upwards for a further 12 inches and then bending 90 degrees to pass through the outside wall to the garden tap. This arrangement means that the “L”-shaped pipe (two 12-inch sections) cannot be drained despite the outside tap being opened and the isolator under the sink being turned off.

Is this an acceptable way to fit an outside tap? Also, should I solve the problem by inserting a drainage tap adjacent to the isolator? If so, what is the best 15mm drainage fitting?

Comments appreciated.
 
Any pictures of the pipework ?
 
Should have an isolation valve and an internal double check valve. Isolate I side, open tap outside, removes most of water and prevents the ice pushing off compression joints.
 
If you can post us some photos that will help our members diagnose!
 
Not the easiest to photograph, However, this shows the pipe concerned, the lowest pipe in the pic Ts off the rising cold water pipe. Disappears briefly behind a waste pipe, then rises vertically to rod left where it passes through the outer wall.
 

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Did you leave the outside tap open ?
 
No internal double check valve either. Doesn't look very plumbery.
Don’t see why there is a need to leave the tap open. Air is compressible and water is not. A double check valve isn’ listed as necessary for an ou5side tap although I suppose there would be no disadvantage.

However, to get back to my question, what should I do to prevent this happening next winter?
 
Don’t see why there is a need to leave the tap open. Air is compressible and water is not. A double check valve isn’ listed as necessary for an ou5side tap although I suppose there would be no disadvantage.

However, to get back to my question, what should I do to prevent this happening next winter?
Course you see why there's a need to leave the tap open. Your leak.

Water regs require an internal double check valve on new installations.

Go on admit it, you did it yourself.
 
Morning!

Thanks for the photos!

I just want to remind everyone to be nice and polite to each other! Happy thoughts people!
 
Could you show a picture of your outside tap. It may be the type that has a built in check valve.

The reason for the check valve is to prevent back siphonage.

If you are not using the outside tap during winter it is best to leave the tap open (after closing the iso valve) in case of freezing conditions so the water in the pipe can expand easily and not ‘blow’ a compression joint or burst the pipe.

Hope this helps.
 
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Could you show a picture of your outside tap. It may be the type that has a built in check valve.

The reason for the check valve is to prevent back siphonage.

If you are not using the outside tap during winter it is best to leave the tap open (after closing the iso valve) in case of freezing conditions so the water in the pipe can expand easily and not ‘blow’ a compression joint or burst the pipe.

Hope this helps.
Could you show a picture of your outside tap. It may be the type that has a built in check valve.

The reason for the check valve is to prevent back siphonage.

If you are not using the outside tap during winter it is best to leave the tap open (after closing the iso valve) in case of freezing conditions so the water in the pipe can expand easily and not ‘blow’ a compression joint or burst the pipe.

Hope this helps.
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).
 
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.
 
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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.
 
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.
 
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.
 

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