Wisdom after the fact – burst pipes

The cold snap that affected us in these parts seems to be on its way out, but it certainly made its presence felt. I must have taken nearly twenty calls over the worst three days of the weather from people with frozen condensate pipes. This will be an issue I will return to in the future.

I also had three calls from people with burst pipes relating to outside taps. The most spectacular was this particular example on a section of 15mm pipe.

burst pipe

This burst is slightly unusual in that they normally split along the length of the pipe, possibly along the seam, for about 10-15 mm. The cause is simple – the mains pressure water in the pipe freezes in the cold, the volume of ice is greater than water, the pressure rises to above the pressure rating of copper pipe according to the source I found.  https://www.engineeringtoolbox.com/copper-tubes-dimensions-pressure-d_84.html. This is in the region of 841 psi or 58 bar – and the pipe splits or bursts. My guess is that the pipe in the picture above is less than 0.7 mm thick.

In this case, the customer hadn’t turned off the internal stop tap. She realised she had a problem when she saw the doormat outside her back door threatening to float away.

So here’s the thing – an outdoor tap should always be fitted with a proper stop tap inside the house so that it can be switched off for the winter months. The best thing to do is to close the stop tap and then open the outdoor tap. This will reduce the pressure in the external pipework so that if it should freeze, it has more chance of having somewhere to go to release the pressure. If it should still burst, you’ll know about it in the spring rather than panicking about water loss in the winter, especially if you are on a meter.


However, what I do find more often than I would like, is that someone has taken a short cut and not fitted the internal stop tap. This means that if the outdoor pipework bursts, you’ll have no option but to turn off the mains water and call an emergency plumber, who are in the habit of charging like wounded rhino’s, unless you are lucky enough to get your regular plumber with a bit of spare time and in a good mood enough to rally to your cause and carry out a mercy mission on your behalf.

Retro fitting a stop tap for an outdoor tap can be problematic, usually because of a lack of space with the existing pipework. Sometimes a compromise solution can be found using a short lever ball valve, but this isn’t ideal.

If you are thinking of having an outdoor tap retro fitted, make sure that you are also getting the all important internal stop tap fitted as part of the job. You are paying good money to have the job done properly, so it’s important that the job is done properly! If you already have an outdoor tap fitted, have a look to see if you also have a stop tap. If you don’t have one, I would urge you to take steps to get something done about it. It’ll be one less worry next time it gets cold.


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