How to Make a DIY Solar Pool Heater

Even during hotter months, stepping into a warm pool is a wonderful feeling. But powering all that heat from your gas or electric system to keep the pool at your preferred temperature can get ridiculously expensive. Luckily, you can make a solar heater for pools that will warm your water with free photons.

A solar heater for a pool can boost the temp of your swimming water all year long, and after the installation, these extra degrees won't cost you a thing. This is both an environmentally friendly and cost friendly option to heat your pool.

Do Solar Pool Heaters Really Work?

Yes, if they're getting sufficient light, solar heaters for pools can significantly increase water temperature. Left on, they can nudge things up a few degrees a day, to a maximum of around 10 to 15.

An above-ground solar pool heater can be a cheap and environmentally friendly method of heating a pool. Once the panels themselves are paid for and installed, you don't need to worry about ever-increasing fuel costs. These will use nothing other than the sun to heat your water to a lovely temperature. These systems are also suitable for heating water if required.

Solar water heaters are also very easy to install and will pay for themselves because they should last for 20 to 30 years or longer.

Is Solar Pool Heating Worth It?

A solar swimming pool heater is dependent on the sun to work. On cool or windy days, it will not give you the best results. However, a solution for this problem is to use a solar pool heater in conjunction with a gas or electric heater. This way, if you do feel like a swim on a cool, cloudy day, you can still warm up the pool.

Picking a Solar Pool Heater

You will normally need to choose a panel that is half as big as the surface of your pool. However, the size will also depend on how much you want to heat the water.

The solar panels used to heat water are normally not covered by glass; this means that you will be interested in unglazed panels. These are actually cheaper than glazed solar panels.

Building a DIY Solar Pool Heater

Step 1 - Plan

First, think about how the solar heater will connect to your pool's plumbing system. A pool without a heater will take water out of the pool and then pump it through a filter, after which it is then returned to the pool. A solar heater will connect in the middle of this system. After the filter, the water is diverted through the heating panel before entering the pool again.

You will need some consideration so you can decide where to install the solar panels. It's just not possible to stick the panels on any roof because these may not be positioned to get enough sunlight. Choosing an area of roof which receives a lot of sunlight for most of the day will provide the most efficient heater. Some roofs won't be able to get enough sunlight.

Determine which way is south, the best direction for any solar installations. If you are in the southern hemisphere, then the panels should face north. Look at the roof layout and ensure the placement will not have any obstructions that will hinder the panels from facing the right direction.

Roof-mounted heat panels that are used to heat water are typically heavy, and some areas require an inspection and permit before you can mount anything like this on your roof.

While it may not be necessary, it's not a bad idea to at least consult with someone regarding solar pool heater installation. This way you can ensure that your roof will support a solar pool heater without coming through the roof.

Step 2 - Assemble the Panels

Warming a pool with solar heat requires a few solar panels hooked up to the filtering/circulating system. These panels can be made from sheets of 3/8” (9 mm) plywood boxed-in with 2x4s around the perimeter (Fig. 1).

Drill two holes in opposite corners of the box through the sides and not too far from the corner, for the inlet and the return. A good coating of exterior black paint inside and out will help draw the heat to warm up the pipes.

The box will accommodate 400 ft (122 m) of 1/2” (12 mm) black polyethylene pipe, but before starting, some accessories should be prepared and ready for use. They can be made from 3/4” x 2 1/2” (19 mm x 64 mm) strapping. You'll need two pieces that are 48” (1220 mm) to make “spacers.”

Eight more pieces about 18” (450 mm) long, and six (or more) at 12” (300 mm) long will be used to hold down the pipe and keep it from collapsing. The two spacers will be positioned parallel to the long sides at about 16” (400 mm) from the edge and center with the ends at about 22” (570 mm) from the end walls. They should only be temporarily fastened in position so that they can be relocated later.

Step 3 - Attach the Pipe

Handling the pipe is a lot easier if the tubing is warm since a cold pipe will have a tendency to form kinks when shaping it around the corners. One end of the 1/2” (12 mm) pipe should first be inserted through one of the holes in the corner of the box, with at least 10” (254 mm) of the end sticking out.

The tubing should then be placed against the long wall first, then arcing around the corner and following the end wall into the next corner where it keeps going around, careful not to create a radius too tight as to kink the tubing.

The 18” (450 mm) strapping is required to hold down the pipe as the work progresses. This is done by “bridging” one end on the pipe and the other end on top of the 48” (1220 mm) spacers, screwing in place with one screw only in its center.

Since the pipe is very soft from the heat, care must be taken not to screw in too tight to avoid flattening and damaging the pipe. While proceeding at coiling the tubing inside the collector panel, the spacers will have to be adjusted and relocated to suit the needs, and usually, more will have to be added, including the shorter pieces, wherever the pipe tends to slide out or overlap.

They must be screwed carefully by placing the screws between two pipes, making sure to separate the two pipes so the screw doesn’t touch and damage the pipe.

The coiling of the tubing around inside the solar panel should continue winding towards the center until all the tubing fits snug and neat looking. Some permanent spacers and hold-downs can then be made more accurately to their proper size, to replace the temporary ones, and re-positioned in their most beneficial locations on the solar panel. Those permanent braces should be primed and painted black prior to installation.

Step 4 - Connect to the Filter

The completed solar panel will hook up to your pool’s filtering/circulating system. The method shown here to hook up provides the pool with hot water from the solar collector as long as the pump is running (Fig. 2).

The inlet of the solar panel takes its feed from the Tee fitting on the 1 1/2” (38 mm) return pipe from the pool filter. The outlet of the solar panel will then run back to the pool passing over its side (Fig. 3).

By installing a valve on the main return line between the Tee fitting to the solar panel and the pool’s return (Fig. 4), enough pressure can be built up by partly closing the valve, to create a flow through the solar collector installed on the roof.

The valve is adjusted by feeling the circulation in the pool return outlet. Before the initial start-up, however, the valve could briefly have to be fully closed, depending how high the solar collector panel is installed, so most or all the pressure pushes the water through to fill the 400’ of pipe with water, and at the same time clearing out the air from inside the system.

When there are multiple units installed, their inlets should all be hooked up in parallel to the same return line from the filter. As long as the return pipes of each solar panel feed directly into the pool, or into a larger pipe that runs back to the pool to avoiding creating a bottleneck restricting the flow, it will work smoothly. In the latter case, the combined surface area of all the smaller pipes should connect to a larger pipe with a surface area equal or larger surface area of all the solar panels’ return pipes.

Step 5 - Glaze the Panel

Another thing with solar panels is that they are sensitive to the ambient temperature around them. If it gets cooler out, whatever warmth was gathered in the pool all day will drop as long as the water runs through the solar panel. If there is a breeze, the wind passing over the pipes will also contribute to a significant heat loss. This can be corrected by glazing the solar panel.

This is done by covering the box with a heavy gauge clear plastic or vinyl thus creating a chamber for the pipe layout (Fig 5). A Temperature Control Switch Thermostat (Fig. 6) is then added to the solar panel to deactivate an N/C (normally closed) solenoid valve (Fig 7) installed along the line running to the solar panel cutting the water flow.

This will ensure that when the water in the solar panel cools down, the flow is stopped. This is where the benefits of solar heat panels are really appreciated.

A Word on Pool Pumps

Ensure that the pool pump you are currently using is large enough to pump water around the solar panels. You might need to upgrade the pump with a more powerful model so that it is capable of pumping water right the way to the solar panels, which are fixed to your roof.

Homemade Solar Pool Heater Kits

You can also purchase a solar heating kit to help you with the project. The main considerations when choosing a solar heating kit are the size of your pool and the power of your pool pump. Purchase a solar heater that is large enough to heat the amount of water in your pool.

Compare the specifications of the solar heater to that of your pool pump to make sure your pump is powerful enough to push water through the solar heater efficiently.

Angles

During the course of the solar pool heater installation, you may need to adjust the orientation and angle of the solar panels. Solar panels need to be pointed at an angle that captures the most sunlight. In general, the tilt of the panels should be equal to the latitude of your location, minus 15 degrees in summer or plus 15 degrees in winter.

These settings can be improved to get the optimum energy from your pool heating solar panels. It’s challenging to set the panels during winter because this is the time of the year that has the least amount of sunlight.

To make the most out of the sunlight available, the panels must be tilted at a certain angle. The best angle during winter is your latitude multiplied by 0.9 plus 29 degrees. The resulting angle is how the panels are to be tilted.

The best angle during summertime is the winter angle less 52.5 degrees. Solar panel angles during the summer are more or less 12 degrees more level than what is recommended.

At a 25 degree latitude during the summertime, solar panels are most of the time tilted slightly to the north. To calculate the angle during spring and autumn, get the latitude and subtract 2.5 degrees.

Solar Heater Maintenance

It is very important, especially if you live in a cold winter climate, to disconnect and store your solar pool heater before the temperature dips below freezing. If you allow water to freeze in the channels of the solar heater, it may cause damage to the panel.

If you own a swimming pool, a solar pool heater is a big step in the direction of energy conservation. Not only will a solar heater save you money by utilizing the earth’s largest source of renewable energy, but it may allow you to get more use out of your swimming pool.

Leaking Issues

If your collection panels are leaking water, you will first need to isolate the tube that has the leak. Cut 1 inch off both headers of the tube with a sharp utility knife. Install a #10 or #12 stainless sheet metal screw that is between ½ inch and ¾ inch long in the hole. Make sure not to over-tighten the screw. This should fix the leak.

If it does not fix it, you may need to contact a repairman. Usually, performing this operation will not interfere with or void your heater’s warranty, but you should always check to make sure before you try to fix a leak yourself.

Flow Rate Issues

The pressure on your pump and filter should increase when the system is turned on. If pressure builds up around your filter and the rate of flow seems very low, first check to make sure that the vinyl inlet and outlet caps were removed during solar heater installation.

If they've already been removed, make sure that they were not accidentally reversed. The inlet should be located at the bottom of the solar panel and the outlet at the top.

Another factor that could affect the flow is a dirty or inadequate filter. If this is the case, clean or replace the filter to eliminate the problem.

Final Thoughts

You could also consider a solar pool cover instead of a heater depending on what your needs are. If you go with the heater, be sure to take good care of it and make sure it is properly maintained, even during times of year when you are not using your pool as much.