Hot water not hot enough? Boost it!

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If your solar water heater doesn’t get enough sunlight, it can have trouble heating your water to the required temperature. This can cause problems in winter, when sunlight is generally weaker and available for fewer hours per day. Generally speaking, a 2-panel 300W solar water heater will heat water to around double the top temperature for the day – so if the maximum temperature is 20°C, water will be heated to around 40°C.

If not addressed, this under-heating can turn into a serious problem: water is heated enough to make it the perfect breeding ground for bacteria that thrive in the human body, but not hot enough to kill the offending bacteria. For example, there have been instances over the last few years of people contracting Legionnaire’s disease from their under-heated water systems.

How hot does my hot water need to be?

Water needs to be heated to at least 60 degrees Celsius to kill the bacteria responsible for Legionnaire’s disease. At that temperature, most other bacteria that can cause harm to humans will also be killed. On cold days, a solar water heater could fall short of that mark by 20-30°C.

Closeup Worker fixing solar water heater on roof

How can I fix this problem?

We recommend a simple system known as a booster. The booster is connected to your water heater and mains electricity or gas supply. It monitors the temperature of the water in your water heater. If the water temperature drops below 60°C, the booster draws from mains power or gas to heat the top 2/3 of the water to the correct temperature.

Won’t that use a lot of electricity or gas?

Not really – the booster only kicks in and uses mains power or gas if the temperature in your water tank goes below 60°. You can turn it on and off as required, so that you’re in control of how often it’s used. In order to minimise the use of the booster system as much as possible, try to schedule any heavy uses of the hot water – for example, laundry and long showers – for the middle of the day, when the solar system is at its peak efficiency. This ensures that you’re using as much of your water heater’s solar capacity as possible.

How can I make sure that the water system is safe?

To help you protect against Legionnaire’s disease and other bacteria thriving in your solar hot water system, we recommend the following:

  • Boost at least once in every 24-hour period. This ensures that bacteria are killed off before they have a chance to reach dangerous levels in the system.
  • Leave the booster system turned on over the colder months – from Mother’s Day to Father’s Day, as a rough guide. Keep in mind that this will not mean that the booster system is constantly heating your water – just that it’s available as needed to boost the solar heating already in place.

Where can I find out more?

Easy – just contact SolaPlumb for a chat with one of our friendly staff members. We can talk you through the options that will suit your particular circumstances.

We are family owned and locally operated plumbing company who specialize in the installation & maintenance of Solar Hot Water Systems on Gold Coast.

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