Risk of freezing
The amount of damage that can be done when water freezes in a pipe and bursts it can be huge so insulating is essential. Pipes, fixtures and cisterns which are exposed to freezing temperatures should be protected. These include cisterns (or tanks as they are often called) in the attic, outside water pipes and taps.
Other less obvious examples such as where the water supply comes up into the house. Supply pipes rising through a solid floor normally only require insulating if they are close to an external wall. Where the pipe rises up through a void under the floor it will be insulated as there is more risk here.
Other considerations include draughts which can have an additional cooling effect, and dripping water which is more likely to freeze. A good example of the later is overflow pipes – in exposed conditions the dripping water from these can freeze and eventually block the outlet.
If you are modifying a plumbing installation, or planning a new one, there are areas which are best avoided if possible: Lofts, air bricks, basements, beneath the ground floor, and any outside locations for obvious reasons.
Water freezing and burst pipes
When water freezes and turns to ice, it expands in size by around 10%. Where this takes place within a pipe, it exerts substantial pressure on the pipe wall and eventually can split it. Water freezing within a compression fitting can exert enough force to push the joint apart. It is only when it thaws that we see the full effect. While it remains frozen, obviously the water won’t escape. However once it melts as temperatures rise, the split in the pipe, or the opened fitting, begins to leak and the amount of potential damage can be enormous.
Draining down to prevent freezing
In some situations, where a water supply is not needed during winter months, and the pipe work is outside, it may be more sensible to drain down the section. A good example of this might be a pipe running externally to supply a garden tap at the back of the house. If the tap is only used in the summer, then rather than lagging the pipe and tap, isolate the supply to the tap and drain off any water for the winter months. With the pipe empty, you’ll be certain not to have a problem.
Various materials are available for protecting pipe work, the most common of which is the ‘foam’ tube type. This comes in standard lengths which are partly pre cut along their length enabling them to be fixed easily to existing pipe work. You should check the manufacturer’s details carefully to ensure that they will give adequate protection.
Starting at one end of the pipe run, feed the insulation on. Continue feeding on subsequent lengths as you work along the pipe. Joins can be secured using insulation tape to ensure that no gaps are allowed to form. A sharp craft knife can be used to cut the insulation tube to length. At elbows and T pieces the insulation may need to be cut to suit. The easiest way is to mitre the pieces by cutting the ends to a 45 degree angle and taping the join. On sweeping bends the insulation will normally flex sufficiently not to require cutting. However small V sections can be cut across the tube to ease these if needs be. At fittings such as stop valves and the like, be sure to protect the entire body of the valve whilst leaving the head free so that it can still be used.
Trace heating pipework
Trace heating applies a low level heat source to pipe runs to prevent the risk of freezing. They are more commonly seen on commercial installations but kits for domestic applications are readily available. The wires of the heating element are laid along the length of the pipe work and are connected via a thermostat. When the temperature drops below a set level, the thermostat causes the elements to be switched on and a small amount of heat is delivered.
Insulating water cisterns
Water tanks (as they are sometimes called) in lofts should be fully insulated. Many manufacturers supply insulating kits for a range of cistern sizes. The insulation will include a top to go over the cistern. It is very important that the base of the cistern is not insulated and there is no loft lagging immediately beneath it. The reason is simple – any heat rising from the room below at this point will help reduce the risk of freezing. Insulation to water storage cisterns actually has an additional purpose. For health reasons, the Water Regulations state that water in storage cisterns should not be allowed to exceed 25 degrees centigrade. The insulation therefore has a double benefit by preventing absorption of heat as well. Be sure to also insulate overflow pipes from water storage cisterns. As mentioned earlier, dripping water from these can lead to ice blockages.