Freezing water pipes in buildings

By The Helpful Engineer / On / In Existing Building Issues

Winter has taken hold early this year, the record for the lowest temperature ever in November has been broken in the last few days. This morning the temperature was -9 degrees Celsius. With that in mind and as this cold weather is due to last at least a week, I think its worth highlighting, and giving more prominence, to a comment about freezing pipes left on this website by Gerd, see below. Thanks again Gerd for your very useful advice.

I have seen a lot of freezing pipes in attics, particularly last winter. A lot of buildings had additional insulation fitted to the attics and walls in the last few years. Whilst this is fantastic in terms of reducing your energy bill, it prevents heat from rising into the attic.
So what can be done?
If the pipes and the tank are insulated regular movement of the water should prevent any freezing. This will happen normally in a house by turning on the taps to wash hands, have showers & baths etc. It won’t however happen in commercial buildings such as schools, offices etc. as these may not be used for 2 weeks at Christmas time. In buildings which are closed for the Christmas period it is therefore suggested to drain the tank and then leave the taps open (no water will flow). The draining can be wasteful, but if the supply to the tank is closed a couple of hours before the holiday break, most of the water will probably be used up by flushing WC’s etc. Any taps connected to mains should only be opened if the mains supply is turned off as well.
Care must be taken to ensure that the heating system has enough water in it to allow it to function, which will prevent freezing. The hot water cylinder may also run dry and it is important to ensure that the immersion is switched off and that the heating system is not trying to heat the empty cylinder.
Only follow this advice if you are sure that no damage will be done by turning off the water. I recommend to ask your plumber before turning off any valves to ensure that no damage is done to the system by draining the pipes.

3 thoughts on “Freezing water pipes in buildings

  1. Heres a thought…say you run the hot water and cold water pipes side by side? Would the heat from one prevent the other from freezing? Then maybe you could construct an insulated cover to go over the tank to stop it freezing.

    Not sure if this is kosher or practical, just a thought.

    Love the blog, keep up the good work!

    1. Thanks for your suggestion to run hot & cold water pipes beside each other. There are a small number of problems with this:
      1. In the summer the cold water may become lukewarm which is not desirable, and can be breeding grounds for legionella.
      2. If the hot water is not flowing in the pipe it will quickly cool down and may therefore not prevent freezing

      Other solutions are available as follows:
      1. A trace heating electric ‘cable’ can be installed along the pipes; controlled by a frost thermostat it will provide heat by ‘burning’ electricity. It can be costly to install, and it could also be expensive to run.
      2. Pipes in the attic could be boxed in, so that they are effectively part of the warm part of the building. The attic insulation would have be installed around the box. Similarly, no insulation should be placed under the water tank, but the tank itself may be insulated.

    2. Hi Conor and thanks for the nice words. Gerd answered your first point, thanks Gerd. With regard to providing an insulated cover to the water tank, this is required as part of the building regulations, but in reality most aren’t installed.

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