Draining down outside tap for winter?

AjayK44 · 23 Nov 2020

The outside tap at my property (1st floor maisonette) is supplied by a pipe going down the outside from loft height. The external pipework is lagged but I want to drain it down for the winter. I have turned off the isolating valve in the loft and opened up the external tap but was surprised when no water remnants from the outside pipe drop came out by virtue of gravity. I'm guessing I need to let air into that pipe in the loft but don't really want to start undoing connections in the loft to enable this. Is there any alternative way to drain it down please?

Apologies if this is a very basic question but any help appreciated.

Thank you.

sircerebus666 · 23 Nov 2020

AjayK44 said:
The outside tap at my property (1st floor maisonette) is supplied by a pipe going down the outside from loft height. The external pipework is lagged but I want to drain it down for the winter. I have turned off the isolating valve in the loft and opened up the external tap but was surprised when no water remnants from the outside pipe drop came out by virtue of gravity. I'm guessing I need to let air into that pipe in the loft but don't really want to start undoing connections in the loft to enable this. Is there any alternative way to drain it down please?

Apologies if this is a very basic question but any help appreciated.

Thank you.

Why were you surprised?

It's basic science , it's due to air pressure, you have created the same effect as dunking a straw into water putting your finger over the end of it and removing the straw , the air pressure holds the water inside the straw because air pressure is stronger than gravity

You need to leave the tap open , close the isolation valve and undo the nut connecting the isolation valve to the external pipework , that will put air in which will release the water, just put a cloth underneath the nut to catch the drips

JimCrow · 23 Nov 2020

Your tap may have a double check valve fitted, it's a two minute job to remove the tap from the wall elbow and refit it in the spring.

AjayK44 · 24 Nov 2020

sircerebus666 said:
Why were you surprised?

It's basic science , it's due to air pressure, you have created the same effect as dunking a straw into water putting your finger over the end of it and removing the straw , the air pressure holds the water inside the straw because air pressure is stronger than gravity

You need to leave the tap open , close the isolation valve and undo the nut connecting the isolation valve to the external pipework , that will put air in which will release the water, just put a cloth underneath the nut to catch the drips

Thank you - I appreciate it was a basic science question. Could I install some form of open/close valve on the out side of the isolation valve in the loft so on future occasions it's just a matter of briefly opening a valve to let air into the pipe rather than disconnecting plumbing?

Hugh Jaleak · 24 Nov 2020

AjayK44 said:
Could I install some form of open/close valve on the out side of the isolation valve in the loft so on future occasions it's just a matter of briefly opening a valve to let air into the pipe rather than disconnecting plumbing?

Yes, just install any suitable fitting that can be used to let air into the pipework. Don't forget to close it again afterwards, and ensure all pipework in the loft is suitably lagged.

AjayK44 · 25 Nov 2020

Hugh Jaleak said:
Yes, just install any suitable fitting that can be used to let air into the pipework. Don't forget to close it again afterwards, and ensure all pipework in the loft is suitably lagged.

Thank you - Any suggestions as to what would be an appropriate fitting to achieve this please?

Hugh Jaleak · 25 Nov 2020

Any valve suitable for mains pressure, probably a lever valve. Seems a bit overkill bit overkill but easier than undoing joints.

Madrab · 26 Nov 2020

The reason water burst pipes as it's freezes is that it expands and has no where to go if the tap is closed. Just leave the tap open and the water will exit out the tap if it does freeze.

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Draining down outside tap for winter?

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