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Insulate hot water systems and pipes


A common way of providing hot water to apartments is from a central hot water system. The system deliver the required hot water to each unit via pipes. Long pipes are often needed to deliver this hot water to the apartments the furthest from the system. A lot of heat can be lost from the water as it travels from the boiler to the apartments.

Insulating the pipes of your hot water distribution system can reduce heat losses by up to 70 per cent. This will save energy and stop you losing money on energy bills.

Insulating pipes

Insulate exposed hot water pipes, especially the first two metres leading out from the hot water system or storage tank. This is known as ‘lagging’.

The normal green lagging that some plumbers use is usually not enough. Pipe insulation should have an R rating of at least 0.3, which is about a 10mm thickness of foam insulation. You can buy pipe insulation from a hardware store. In colder areas a higher insulation (R) between 0.6 and 1.0 rating is desirable.

Care should be taken to ensure the insulation is continuous, covering all joints and bends. The insulation should be well taped to hold it in place so that it does not fall off over time. If located outside a protective sheathing over the insulation is recommended.

The PT (pressure/temperature) valve on the side of a storage tank will have a short pipe running to a drain that bleeds off hot water to relieve pressure. This should also be insulated as it is a direct thermal connection through the insulated wall of the tank. Contact a plumber or handyman to obtain a quote.


The cost of pipe insulation will vary based on whether the pipes are located externally or internally, and access. Basic foam insulation will cost about $3.50 a metre and can be installed by a handyman. External pipe insulation is more expensive and would require a specialised contractor to install.

Blankets for electric hot water heaters

You can reduce heat loss from electric hot water heaters by wrapping the storage tank with an insulation blanket. Insulation blankets are not suitable for gas storage systems. When insulating the storage tank make sure the insulation doesn’t restrict the flues or air vents around the hot water system. You should also check with the manufacturer to ensure the warranty won't be affected before installing extra insulation

Note that the storage tank and pipes in solar hot water systems are very likely to need protection from frost in cold and temperate climates. 

Lower the temperature

Once you have insulated your pipes and storage tank you will be able to lower the temperature of your hot water system and stop losing money on energy bills. This is because the water won’t need to be heated to such a high temperature if the heat is not being lost in the time it takes to reach each apartment.