DIY Solar Pool Heater

Updated February 21, 2017

Summer brings great pleasures: barbecues, family gatherings, outdoor sports and swimming. Families with swimming pools can enjoy a mini-vacation in their own backyard. In many parts of the country, however, the summer is a rather short season, and while the air temperature in the early spring and the late fall can be mild, pool water can be chilly. Extend your swimming season with a do-it-yourself solar pool heater.

The Basic Flow

Since you already have a pump for your pool, make a break in the return line from the filter to the pool (not BEFORE the filter so that warm water directly from the collector does not circulate through the filter). Insert two "T" joints in the line, with a valve in between. A pipe from the first "T" joint will send water to a solar collector. The second "T" joint will be the return from the collector. A valve inserted between the two "Ts" is used to control how much water will be diverted to the solar collector. During the evening when there is no sun, you do not want to send any water through the solar collectors, nor do you want to circulate water through them when the pool reaches the temperature you want.

The Collector

The heart of the system is one or more solar collector units. In its simplest form, it is a large box painted black in which black PVC pipe is "snaked" back and forth for maximum exposure to the sun. A glass cover keeps the air temperature warm inside the box. You can do it yourself and build your own solar collector box. Use black PVC pipe with the same diameter as existing pump lines. Connecting collars and couplings can be secured with either glue (allow a 24-hour drying time) or with stainless steel clamps. Purchase a commercial collector and install it yourself. Commercial units are designed to be very efficient and will hold up to the rigours of weather. In either case, basic plumbing skills and the proper tools are required.

Mounting the Collector

Solar pool collectors can be mounted on the roof of a house, on the roof of a tool shed or building that houses the pool pump and filter, or even flat on the ground. Ground installations that are close to the pool usually require the least amount of work to construct. Do not install collectors on roofs unless you are capable of working on roofs and take all safety precautions. Roof collectors must be securely attached to withstand strong winds. The larger you build the collector, the more heat it will produce, but you must have the available roof or ground space. Collectors should be installed facing south; make sure the collector is not ever shaded by trees or buildings while the sun is out. East and west orientations are usually acceptable, but north-facing panels are too inefficient to use.

Safety Valves and Drainage Openings

It is advisable to also install manual valves on both the send and return lines to the collector to be able to disconnect it for service. Also, be sure to have a way to drain the water from a collector for winter preparation. This can be done simply by using couplings with removable clamps so you can access the pipe.

Pool Covers Retain Heat

Pool covers are not very expensive and can be placed over the pool at night to help keep the heat, which the collector has produced during the day, in the water. Consider the pool water itself as a giant solar heat storage tank!

Automated Controls

If you want to build a more sophisticated and automated system, consider companies such as Solar Direct (, which sells pool heater controls, sensors and motorised valves. Some electrical knowledge is also needed for installation, but such a system automates the flow water to the solar collector. If the temperature in the pool is warm enough, the system can automatically bypass the solar collector. When the temperature in the solar collector is cool, as it would be at night, the system can automatically bypass the collectors.

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About the Author

Dan Keen is the publisher and editor of a county newspaper in New Jersey. For over 30 years he has written books and magazine articles for such publishers as McGraw-Hill. Keen holds a degree in electronics, was chief engineer for two radio stations and taught computer science at Stockton State College.