There are several ways to heat your pool and spa but the determining factor on which ones to choose depends on your intended use! Your pool will always be close to ocean temperatures without heating it due to ambient temperature and ground temperature.
Ocean Temperatures Melbourne: average in feb 17deg c -23deg c, average in jul, 10deg c – 14deg c.
Typical temperatures at a public swimming pool.
Lap swimming pool 25-28deg c
Recreational pool 28-32deg c
Kiddies play pool 32-35deg c
Spa 38-40deg c
Heating your spa:
Most people make the decision to have a spa at the spare of the moment. No body wants to wait hours for their spa to get to 38deg c. They will end up losing interest. So, the only way to heat your spa fast is with a large volume gas heater. A 400mj gas heater will take a approx. 15-20mins to heat a 2000litre spa from 15deg c to 38deg c without a cover on it. You could use a large electric element heater, but this would take a lot longer i.e.: 24kw heater approximately 1.5 hours.
Heating your pool:
Solar heating: This is the most cost-efficient way of heating your pool during the summer months, oct -april. You only have the running cost of a 3-4amp pump circulating the water through matting or panels on top of your roof. However, it is dependent on your roof temperatures from the direct sunlight.
Gas Heating: If you have a spa, you will most likely have a large gas heater which is also connected to your pool through 3-way valves. So, it’s possible to heat your pool and spa together. Obviously, you would be heating around 42,000litres of water on an 7×4 average pool. and this would take approx 8hrs for a 15deg c temperature rise without a cover. You are now required by the Victorian Building Authority to have a pool cover if you intend to heat your pool with gas.
Invertor Heat Pump: Invertor heat pumps are becoming increasingly popular. However, they are just an electrical element like a kettle but with an invertor part that also generates heat with a reverse refrigeration process using gas refrigerant. They are most efficient in hi humidity environments. But!
if you are intending on having solar collectors and electricity battery storage and have no roof space for solar matting, they are a great option. However, it is now a Victorian Building Authority requirement you must have a pool cover if you intend to use one. Without a cover most units are too slow and wont be able to maintain and build on the heat lost with cooler ambient temperatures.
Heat Exchanger: Commercial pools often use large gas boilers with separate heat exchangers which keeps the pool water separate to the boiler water. This same method can be used with insulated storage tanks with heat exchanger coils within or separate exchanger with circulation pump. Utilising your house hydronic heating or solar hot water heating. The pool water can’t be mixed with these systems due to the salt content and corrosive properties so a stainless or titanium heat exchanger is a great option.
Geothermal: A hi end heating solution is utilising the ground beneath natural constant temperatures. Around 100metres below there is a constant 25deg c that can be utilised by drilling down and circulating water through a heat conductive pipe, this is extremely efficient but a big initial outlay.
Heat Loss: As heat rises and exits your pool water, outside ambient temperatures play a big part in heating. Overnight heat loss is a major factor in maintaining a comfortable swimming temperature in your pool. Having a cover on your pool and spa is the best running cost investment you could choose no matter what heater you choose to use. This will not only minimise heat loss but can actually accelerate solar heat with some covers. Check out our Pool cover section for more info!