Solar Swimming Pool Heater

Last summer we installed a swimming pool in the back yard.  We love the pool but there were times when we would have liked the water to be warmer.  We live in Northern Virginia near the Blue Ridge mountains so most evenings the outdoor air temperature is comfortable enough to sit outside.  Although cool evenings are nice for sitting on the deck, the cool air can drop the temperature of your pool several degrees overnight.    One option was to use a propane heater to heat the water.  Now I like to be comfortable but I just can't bring myself to burn fossil fuels to heat 10,000 gallons of water just so I can swim in warm water. 

After a lot of reading and research I decided to use solar panels to heat our pool water.  There were two goals for the solar heating system; Give the pool water a "bump" in temperature on summer days so we can swim comfortably all day and into the evening and extend the pool season by a few weeks at each end.  I figured that since I need to run the pump/filter system for several hours a day anyway why not pick up some heat from the roof. 

I spent about 45 minutes on the phone with the knowledgeable staff at Solar Services and felt confident that solar was the way to go.  The solar panels would integrate into the existing pool plumbing and be controlled by my Aqua Logic pool controller ( .  We purchase four 4' X 8' panels made by Solar Industries from a local dealer named Solar Services in Virginia Beach, VA. 

Pool Details -

The pool is a 15' x 33' in-ground fiberglass pool with a 10,400 gallon capacity.  The pool is in full sun from 10:00 in the morning till about 4:30 in the afternoon.  Evaporation is the biggest factor in keeping a pool warm.  On warm days with low humidity the pool can loose 1/4" of water and several degrees.  We used a solar blanket for the first week to prevent evaporation but soon abandoned its use because it is such a pain to remove.  .

Performance Results

Before I get to the project details I want provide data on how the system is working.  I know when I was searching the Internet for information on solar pool heating the one thing I never found was performance data like you will see listed below.  The lack of information made it difficult to know if solar heating would work for us.

So how well does it work?  Frankly I am impressed.  We had a solar blanket (aka bubble wrap) on the pool for the last week and only picked up 1-2 degrees.  I was shocked when I went out to the pool controller Saturday morning when the air temp was 65 degrees but the solar sensor on the roof of the shed was already at 94 degrees.  I programmed the system and started it up.  The system started running Saturday morning at 10:00 am and by 3:00 on Sunday we had climbed 8 degrees (67->75)!!  We raised the water temperature of 10,400 gallons of water 8 degrees. 

The month of May (2008) has been one of the coolest on record here in northern Virginia.  We received over 8 inches of rain this month with night-time temps dropping into the 30s and 40s and only holding above 60 one night.  The data below is running the system from 9:30-3:30 each day unless it was raining.  I suspect once we get into a summer pattern where the temps stay in the 70s overnight maintaining a more constant pool temp will be easy.

The table below has the actual data I collected.  I'll be keeping this up for a few weeks until  I can get a feel how the system does under the different conditions.

Current Month

    No Data for 2009 - Review Spring 2008 Data Below

                     Air Temperature Pool Temperature  
Date Low High Low High Comments

Previous Data

  Data From Spring 2008


The following sections shows the construction details for the project.  It took two weekends to complete.  The project was a lot of fun but it took a great deal of planning.

We are fortunate because I have a good size shed (12 X 20) next to my pool equipment where I could mount the solar panels.  The panels are in direct sun from 9:30 AM until 4:00 PM each day.  The project seemed simple enough.  Order some solar panels, mount them on the shed roof, do some plumbing and swim in warm water.  Like I said, it seemed simple enough...

So the panels show up, I unpack everything, line up a neighbor's son to help.  I put the ladder up against the shed placed a foot over on the roof and WHOAAA!  No traction!  The shed does not look that steep from the ground but once up on a ladder and faced with actually working up there it may as well have been a church steeple.  I knew one thing for sure, a "full figured" guy like me would not be working on the roof.  Now what...  I called a friend of mine named Chris that has "mad roof skillz" and he said he would be glad to help.  Chris and I got the panels mounted on the roof the first day and began the plumbing.

Click for larger image       click for larger image 

The system integrates with the existing pool plumbing and uses an electric diverter valve to send water to the solar collectors when the roof is producing heat.  The pool controller has an air temperature  sensor, a pool water temperature sensor and a sensor you mount on the roof near the panels to measure the roof temperature.  The logic works like this:

If the roof is producing heat, and the pool water has not reached the desired temperature, then divert the water through the solar collectors.  Conversely, if the water has reached the desired temperature or the roof is not hot, send the water directly to the pool.  The diverter valve can be seen in the photo below.  The diverter valve is the rectangular black box, above that is a check valve and above that an isolation valve (ball valve) in case I need to service the solar collectors.  The right stack is the return from the collectors with another check valve and a clean out stub I use to pump water out the pool.


Here you can see the whole system, pump, filter, valves and controller.

The rear shed door presented a challenge.  At some point I am going to remove the door and replace it with a wall but in the mean time I had no where to mount the pipes.  So I sent them to the roof the roof at an angle to avoid the door and reduce the number of elbows (and head pressure) in the system.



The completed Project can be seen below.