About 30% of the energy used to heat water in a storage system is wasted due to heat loss from the tank and associated pipework. This can be reduced through careful design and installation.
Keep hot water pipes as short as possible to minimise heat loss. In new or renovated homes, locate wet areas close together with the water heater close to all points of hot water use. If this is not possible, locate it close to the kitchen where small, frequent amounts of hot water are used. Another alternative is to install a water recirculation system. These systems are generally compatible with any hot water system type. They recirculate water in the pipes until hot water is detected, to avoid wastage.
Estimate your hot water needs accurately to ensure your system is not oversized or undersized for your household. If storage system tanks are too small for the number of people in the house hot water can run out. If the tank is too large, operating costs will be excessive. Storage systems lose heat through the tank walls. Reduce heat loss from electric hot water heaters by wrapping the tank with an insulation blanket. Insulation blankets are unsuitable for gas storage systems.
Insulate hot water pipes, particularly externally exposed pipe leading from the water heater to the house and the pipe leading to the relief valve (on storage systems). Note: Standard green lagged hot water pipes are
inadequate for external protection in cold and cool temperate climates. Apply additional insulation or ‘lagging’. At least 10mm of foam insulation is needed The tempering valve, required to limit hot water to 50°C to prevent scolding, should be located as close as possible to the tank to minimise pipe heat losses. Be sure to comply with your state or territory government requirements.
For storage systems, consider installing a timer to ensure water is not heated when it’s not needed, and a switch so the system can be turned off when you go on holiday. Design new homes with a roof pitch and orientation suitable for a solar water heater. You may not want to install one now but it leaves the option open for the future. A north-facing roof with a pitch of between 22° and 40° is usually adequate.
A complete thermosiphon system, when full of water, can weigh several hundred kilograms. Most roofs can support a storage tank without reinforcement but you need to check this before installation. Talk to your builder, designer or engineer to find out.
Be sure to insulate all components, including pipes, to get the best performance from your system. This is particularly important for thermosiphon systems where there is a long distance between the tank and the hot water taps. It is critical in cold climates.
Make sure the booster control is in an accessible location and has an indicator light you can see from inside to remind you to turn it off when not required.
Operating and Maintaining Your System
- Follow the manufacturer’s maintenance recommendations.
- Set the temperature of your booster thermostat to 60°C. A lower setting may allow the growth of harmful legionella bacteria.
- In favourable climates during summer, water temperatures in a solar water heater can approach boiling point. Heat dissipation devices may be required to prevent water from boiling.
- It may also be necessary to fit a mixing valve to reduce water temperatures experienced at the tap to safe levels during summer.
- Carry out jobs that need hot water early in the day so that the water left in the tank will be reheated by the sun, ready for use at night.
- Regularly clean solar panels to remove dust. You can use a broom with some detergent to give them a scrub.
- Flush out collectors to remove sludge. Heat pump systems do not require flushing.
- Make sure you turn the booster off when going on holidays and consider turning it off during summer if conditions are favourable.