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Open loop system or closed solar pool water heaters

Open loop system or closed solar pool water heaters? What does this mean and how do I know which is best suited for my set up?

When it comes to using the solar to heat your pool there are two types of systems that will work to get the job done but each are specific to the individual needs of the customer. Not only will they save you money with electricity bills, but these systems help reduce our carbon footprint. With the era of constant progressing technology, we are finding new more efficient ways to utilize the natural resources available to us. Take advantage of the industries best systems in solar pool heating so you can turn the massive heat energy from the sun into something useful for you and your family.

With that comes the important question:

What are the differences between the two systems and how do I know which will work best for me?


An open loop solar pool system heats the water directly from your pool being added to the current loop system. During normal pool operation the water will circulate through the solar collectors in the existing filter and heating loop. When energy is being demanded to heat the pool, the water will flow into the filter and existing heater, then top up what is needed to heat the water to your desired set temperature. In turn, if the solar is supplying the needed temperature the now secondary backup heater will not have to be used. When your pool is at the required temp the system simply bypasses the solar loop to prevent overheating.

Open Loop



Lower setup costs

Less reliable and accurate

More energy consumed by pool pump

Don’t work in cloud or cold weather

Chemicals/salt water can damage equipment

Frequently leaks can damage roof


A closed loop solar pool system is a pressurized system separate from the pool loop. Instead of using water, the fluid used in the collectors is an environmentally friendly antifreeze solution containing water, propylene, and glycol. This mixture circulates through the collectors then transfers the heat energy to the pool water via a stainless steel or titanium heat exchanger. The pool circuits meet up in parallel through the heat exchanger where solar energy is transferred to the pool water through the collector system. Any additional energy required is supplied by the existing heater before returning to the pool. To protect the system from overheating, the circulating pump is turned off putting the system into a “Stagnation” state. The fluid in the collectors turns to steam which is then absorbed by the added expansion tank in the loop. This system is more commonly used in colder climates, year-round pools as well as indoor solar pool heating setups.

Close Loop



More reliable/accurate

Higher initial cost

Smaller circulating pump using less energy

Can be used year-round indoor or outdoor

Can easily be integrated into multiple systems (in floor radiant DHW)

Long life expectancy – no interaction with pool chemicals

In conclusion, when you are deciding which solar pool heater is best for you it all bottoms down to the factor’s dependent on what’s best for your setup.

Although if you had to pick the system that is the most reliable and uses the most advanced solar technology, then the closed loop system would be the choice. It’s no mystery that solar heat energy is the most modern, efficient way of heating a pool so it makes sense that you would want the most profitable system to optimize your return.


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