Swimming Pool Solar Water Heaters 
Guide
(updated 2018)

A swimming pool solar water heater system is one of the simplest and most economical applications for free sun heat usage that does not require high initial investment, but it provides faster payback than most of the other systems.

Solar pool water heater - basics

Solar pool water heaterSolar pool water heater

The solar pool heating system is the right choice if planning to heat the swimming pool in and off the season (extended swim season), where the free solar energy is utilized to increase the pool water temperature. The system uses both direct and diffuse solar radiation, so even if you don’t live in southern parts you can still take advantage of the solar heating system.

Keep in mind that the unheated pool will have the temperature a little above the outdoor temperature (if located in the southern warmer regions).

The swimming pool solar water heater has to be properly sized and provide the desired temperature. If not, then the backup boiler has to be used.

The most popular pool solar heating system is where the solar panel is made of black polypropylene (PP) plastic, rigid or with the individual pipes and usually roof mounted. Water is inside the collectors only when it circulates through. This is why this system is called the Drainback system, as seen in domestic solar water heating. This is helpful in the winter time so chances of water freezing inside the solar panel and pipes are significantly reduced.

The system uses the water pump and filter to circulate and filter the water from impurities.

Advantages

Solar heating is the natural, environment-friendly and cost-effective way to heat the pool. It has no running costs and maintenance is very low.

Solar systems are capable of increasing the temperature of pool water up to 50 F, but it depends on many factors, such as the area where it is installed, the area size of the pool and panels, orientation, color, roof construction, climate and other.

The main advantages of the solar water heater for pools are that the required temperature is lower than for domestic hot water production, and the absence of the separate storage tank. It helps the homeowner prolong the swimming season. As there is no flame, gas and venting, solar heaters, by using the renewable free energy they are considered environment-friendly.

Here are other reasons why to buy and install a swimming pool solar water heater system:

  • Low initial cost
  • Low annual operating costs
  • Easy to install
  • Solar pool heating systems are efficient and durable
  • Maintenance-free systems
  • Faster payback
  • Long lifespan

Parts

The main components of the swimming pool solar water heater system are:

  • Solar collectors
  • Pump
  • Filter
  • Controllers (i.e. to compare incoming and outgoing water temperature).
  • Fittings
  • Valves

Solar collectors

A pool solar collector is probably the most important part of the heating system and this is the place where the sun heats the panels and water inside the tubes.

Unglazed type

If the solar panel is made of plastic and rubber and doesn’t have glass coating, it is called unglazed solar panel (soft type). It looks like a rubber mat with the tubes that carry water. It is made of the heavy-duty materials and due to its flexibility, it can be installed virtually anywhere, including uneven surfaces. These are recommended in areas with the warmer climates. In regions with the colder weather, they can also be used, but only as the Drainback system, so water is removed when it is cold.

Soft solar collectors are usually roof mounted or close to the up, and are designed to heat large amounts of water to relatively low temperatures, which is between 80 and 90 F. This is achievable due to the material used, which is polypropylene. This cheap material allows pool solar water heater to be affordable over expensive version with copper tubes. Another reason to achieve "low" water pool temperature is its unglazed setup.

This type of the collectors is also known as the low-temperature collectors and as they are simple and inexpensive, they offer a good return on investment.

The problem with the unglazed or uninsulated collectors is the incapability of the collector to produce any heat during the winter time.

Due to the limited operating temperature, which is usually between 220 F and 240 F, polypropylene solar collectors cannot be installed inside the glazed box to increase the efficiency as the manufacturer will void the warranty.

Standard sizes for pool collectors are 4 feet wide and 8, 10 and 12 feet in length. Top and bottom tubes are called header tubes with the size of 1,5" or 2" connected with the risers, 1/4" in diameter. The solar panel is through the headers connected to the PVC pipes by the rubber couplings and hose metal clamps.

The glazed type (hard type), on the other hand, comes with the iron-tempered glass coating, aluminum plate and copper tubing running through it. The typical setup includes the series of several flat black panels where more units can be added if the larger area is needed. These are more efficient than unglazed systems and the advantage is that they can be used throughout the year.

Circulation pumps

Circulation pumps are used to transfer water from the swimming pool, through the filter, to the solar collectors and back.

Filtration system

As explained, the pump is used to transfer the pool water to the solar panels where it is heated by the solar radiation and then returned to the pool. Before the water goes to the solar collector, it has to go first through the filter to remove debris and clean water. On its way back to the pool, it will usually go through the backup heater and the chlorinator if they are used.

As the mentioned heating system is the Drainback system, when the pump is turned off, water from the collectors drains down to the pool.

Automation

Some systems can be automated. They can use sensors and valves to direct water through the collectors or bypass if heating is not needed.

Popular kits

If you are handy at plumbing and electrical wiring, it is very easy to build and/or install a swimming pool solar water heater. Simply buy the solar water heater kit and the rest is like a puzzle. Use the glue and hose clamps to put the system together.

Sizing tips

How will you determine the size of the solar panel? According to the experts, the total area of the panel should cover at least 50% of the pool's surface area (for example if the pool area is 800 sq.ft., the collector should be at least 400 sq. ft). This rough calculation assumes the southern warmer regions (Florida, Texas), if the panel is properly oriented and if there are no shaded parts in the pool. Otherwise, you have to increase the exposed area of the solar panel.

Use the following formulas to calculate the area of the pool:

Rectangular shape: LxW (L-length, W-width). If the pool is 5’x10’, the pool area is 50 sq.ft.

Round shape: 3.14xRxR (R=D/2, where D is pool diameter, R-stands for radius). If the pool is 24 ft., the area is 3.14x12x12=452 sq.ft.

Other factors that should be taken into account when selecting the right panel size are the desired temperature of pool water, direct sun and wind exposure, other weather conditions, using the solar blanket, sensor, valves, and controllers. By using the electronics, the system becomes automatic which increases the performance and efficiency. For example, during the colder weather water is not heated and energy losses are prevented. 

Install the solar collectors so they will face south and tilted at an angle equal to the latitude of the pool's location minus 15 degrees (summer). Best conditions include south direction and receiving an average of 6 hours of direct sun per day. Remember that for regions with less sunny days, more panels should be added, provide the same results.

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Cost

To buy a DIY solar water heater kit, size of 300-400 sq. ft., expect to pay from $1500 to $2500 that depends on the complexity of your system and the pool size. But if you want someone else to install it for you, it will cost you double. Warranty from the manufacturer is usually 10-15 years, which depends on the quality of the UV screening materials (inhibitors) and predicted payback period is 2-7 years.

Tips to save

Most of the heat loss, which is over 70%, from a swimming pool is caused by evaporation of water from the surface. Warm water evaporates more rapidly than cool. To reduce the heat loss during the evaporation, buy a good quality pool cover and save.

The heat loss is directly proportionate to wind velocities, pool temperature, humidity and air temperature. The most important factor is to have the swimming pool installed in a sunny spot as more than 75% of the solar energy is absorbed by the pool water.

Keep in mind to properly size your swimming pool solar water heater so the heating system can have the minimum of the heat loss and maximum heat gain. Take into account the location of the swimming pool, shades, winds, and is the panel oriented to the south.

Homemade project examples

Andy made this DIY solar pool heater from 100 ft. coils of half-inch plastic pipe for the pool size 30 feet x 12 feet x 4 feet average depth and 11,000 gallons. Solar panels are installed on the roof and due to the roof layout are facing east. This panel was built 5 years ago and the cost to build was around $300 for tubing and PVC but the framing materials came from scrap... more.

Another simple homemade pool solar water heater made by Fraser located somewhere in Spain. He built the heater for 70 Euros for the pool size of 60 m3 and 1 m3 insulated hot tub while keeping the temperature of 35 C year round... more

How to build a solar pool water heater from Instructables.

Summary

Good-quality solar pool heaters are made of high-quality materials for durability, are versatile that can be installed on different objects; roof, shed, ground, rack; are easy to install and re-install; have a long warranty, have low maintenance and provide very low operational costs. 

According to many reviews, solar pool heaters are dependable, simple to install and economical. The upfront price might be higher, but the savings the system offers can compensate the cost.

The recommendation is to have the licensed professional install the solar heating system, while DIY installation kit is also available and not a big deal for a handyman.

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