Hot water leaves the top of the tank in a copper pipe. Copper, being a metal, conducts heat along the pipe, and the heat is then lost to the environment.

The outlet pipes should be wrapped with pipe insulation as this slows the conduction as well as helping hot water inside the pipe retain its heat for longer.

The easiest insulation to use is tube-style closed cell rubber foam slit down the length. Wait for the hot-water pipes to cool down before installing. Cut the insulation tube to fit the pipe length as required, and slip it over the pipe.

Measure the pipe diameter before buying the insulation to make sure you choose the right size (12, 15 or 20mm). Use tape or nylon ties to hold the insulation in place. Insulate elbows and right up to the tank as best you can.

Ideally all exposed hot water pipes should be insulated. However the first 2 metres are the most crucial sections of the pipe, especially if the outlet pipe leaves the tank and heads upwards as the pipe works more like a chimney.

Hot water outlet pipes are typically 13mm diameter.

CLICK HERE for further information on installing pipe insulation from US Department of Energy.

Note: if foam pipe is used outside it will perish with exposure to weather and UV over several years and will requrie replacement. The insulation foam however is low cost and therefore not a big job to redo every few years. 

Available products

The most available insulation is Armaflex foam pipe. It is available in 2 m lengths and costs around $5 - 8 per length, depending on retailer and thickness. Check the diameter of your pipe first as it is available in various sizes (usual diameter is 1/2" or 13 mm). Various wall thicknesses are also available, the thicker the better.

A self sealing pipe insulation,  Amarflex self sealing insulation pipe is a newer product and becoming more available. The pipe comes pre-split with adhesive allowing ease of installation.

Armaflex DuoSolar and Armaflex Solar  is designed to insulate pipes in solar hot water systems and is UV stabilised and tolerant of high temperatures generated from solar system. While appropriate for use on standard cylinder, it is sold by the coil for installers, and therefore not so useful for the home handy use.

An alternative closed cell rubber foam available from Bunnings in 1 m lengths (~$3, K-flex or Handitube). Various diameters are available but only one 13 mmID and 9 mm OD,