Given the recent extreme weather in Britain, you may be wondering if this can affect a rainwater harvesting system. The answer is no, providing you take a few simple precautions. This article will guide you through.
Let’s look at the components involved, and any possible problems.
Rainwater Storage Tank
If you have an underground tank for storing rainwater, the water inside will rarely freeze, except in the most extreme circumstances, and then only the top surface. This is because it is insulated by the backfilling material and the earth surrounding it. In fact, the water will be kept at a fairly constant temperature.
However, if your system uses an above-ground tank, you will certainly need to take extra measures to protect the pump. Ideally the tank should be a pre-insulated model, otherwise it is possible that in periods of prolonged cold weather, the water in the tank could begin to freeze. This in turn could damage the pump within the tank. There are two options to avoid this, depending on the type of system you have. If you have a simple garden system that is only used in the growing season, you can drain the tank and remove the pump each winter. If your system needs to operate all year round, and your tank is not pre-insulated you can insulate the tank to prevent freezing. This can be something as simple as bags stuffed with straw, or surrounding with rigid insulation sheets, or perhaps a proprietary ‘jacket’. It is important to insulate all exposed pipe work as well.
All rainwater system has a filter collector unit, this will usually be located below ground, though sometimes will be fitted into the rainwater downpipe above ground level. The filter will not be affected by severe cold weather; if the water passing through it freezes, the filter will simply stop collecting water. When the ice melts, the filter will begin to work once again. Of course, snow on the roof will not pass through to the filter, but once the thaw begins, then it will melt and enter the system in the normal way.
The Control Unit
This should always be installed in a dry, frost-free environment. It is not designed to be installed outside, but if is installed in a garage or outbuilding, make sure it is well insulated. Ideally, place it inside in a utility room or kitchen cupboard, along with the mains water top-up unit.
If your system is an indirect system, it will have a header tank, probably in the loft. This must be insulated, both against freezing in winter, but also against the heat of summer. Water that is allowed to get too warm is more likely to permit the growth of undesirable organisms. Insulation jackets are widely available and are easy to install.
If your system also includes UV equipment, this must be protected against frost. Freezing water can easily damage lamps and the housings of the pre-filters.
Are High Temperatures A Problem?
Not so much in this country! Again, water in an underground storage tank will stay at a relatively constant temperature. Water in above ground uninsulated tanks may rise in temperature during hot weather, particularly if exposed directly to the sun, but this will generally not be detrimental for garden water systems. However, if you have an above ground tank that is supplying water for the house, then the tank should definitely be insulated or shielded from the sun.
To conclude, the common sense approach is to insulate tanks that are above ground, whilst underground tanks rarely need it, if ever. The most important thing though is to ensure that any pipework is adequately protected.
More information about rainwater harvesting systems, including design considerations, capacity and cost, can be found in our guide Everything You Need To Know About Choosing A Rainwater Harvesting System. Access a free download today by clicking here.