DIY Pool Heater

Simple DIY Pool Heater that Anyone Can Build (Above Ground Solar)

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After another year of not getting my pool above 73-degrees I decided to tackle a DIY pool heater. And after a few days thought on how to build one that wouldn’t ruin the lawn, maximized heat capture and used garden hoses I could re-use later I have one installed with just a few hours collecting parts and assembly.

First, my kids will swim in 70-degree water.

But I just can’t do it. 

And living in a northern climate the season is short to setup, use and then put away a pool. Which makes heating a must but I don’t want to invest in an expensive heater. And the large solar heaters* that I figured would work best take up too much space.

So, this year, I decided to put my woodworking and design skills to use and build my own. 

While I did look at buying the factory kits the reviews scared me off. And I also have a lawn I don’t want killed by black mats. 

In this article I’ll show you:

  • Supplies you’ll need
  • How to build the platform
  • What types of hoses
  • How I connected to my pool
  • Temperature results (I saw a rise of 67 to 90-degrees in my first hot afternoon test!)
And, of course, you’ll need to use a solar cover to avoid losing the heat you gained.
Best Selling Solar Covers

Last update on 2020-09-23 at 13:03 / Affiliate links / Images from Amazon Product Advertising API

Supplies Needed to Build a DIY Pool Heater

DIY Pool Heater Solar Domes
Solar Heat Domes to Retain Heat

Let’s get started!

Here’s what you’ll need to build this DIY pool heater:

  • 1- 4×8 sheet of plywood
  • 2 – 2x4x96″‘ treated or cedar boards
  • 1 – 4x4x48″ treated post
  • 1 – 1-1/2 x 1-1/2 x 96″ cedar or treated
  • Screws: 1-1/4″, 2″ and 3″
  • 2 – solar domes like these Solar Skylights* (check a local big box store – 25-1/2 square is best)
  • 3 – 100′ kink free hoses*
  • 2 cans of black semi-gloss paint
  • 10′ of 1/8″ inside diameter Pex tubing
  • A collection of pool hoses* and plumbing parts (based on your pool)

My workshop has a variety of wood, and to keep cost down I used a mixture of cedar, brown treat and OSB for my project. 

If it all goes well and I keep this 3+ years perhaps I’ll regret the OSB, but it was on-hand.

Sometimes it’s best to use what you have vs. fretting about it rotting outside!

How a Solar Pool Heater Works

Before we get building, it’s worth understanding the basics of this type of heater.

And there are dozens of options for building a DIY solar heater, but I haven’t found any that don’t involve unsightly tubes attached to raw plywood.

Or flat plastic mats that would destroy my grass (and pop if placed on my mulch).

Here’s the basics:

  1. The game is all about TEMPERATURE RISE. If water comes in at 70-degrees and goes out at 74-degrees you have achieved RISE.
  2. Circulate enough water and eventually 70-degrees in turns into 72-degrees in.
  3. Black hoses conduct heat, and running water through them converts that heat to the water

When won’t this work? Well, without the sun. But also if you can’t achieve enough flow through the hoses.

Step 1 - Building the Heater Box

After searching and searching for a factory solar heater that didn’t require killing my grass I decided on building my own. 

And using an elevated box.

In this step you’ll need to:

  • Make a 25-1/2″ x 50″ box out of the 2×4’s and plywood
  • Install four 4×4 legs
  • Drill a hole on each side for the hoses
  • Paint the box black along the way for absorbing the heat.

While I could have made this project completely from cedar, like the deck and porch I’ve built, I decided making sure this worked was job #1. 

Making Entry and Exit Holes for the Hoses

DIY Pool Heater Hose Entry and Exits

Since the top of the enclosure will have the solar heat domes you’ll need to make holes in the side for the hoses to enter and exit.

For this step I used a 1-1/2″ spade bit. And drilled a hole in the upper left and one again in the lower left.

Step #2 - Installing the Hoses in the DIY Pool Heater

I thought about how to do this a lot for my DIY pool heater to work properly.

For days, actually.

My first thought was running black pipe between the sides to suspend the hose. But, decided against that as the hoses would expand and sag. 

Plus I’d lose surface area of the hose – which is the #1 name of the game with a solar system.

So, I decided to lay the hoses flat and use a nylon bushing to hold them in place during assembly (keep reading for a trick on how I later hid these).

Weaving the Hoses

DIY Pool Heater Assembling the Hoses

So how do you keep the hoses in place? After deliberation I decided I needed to use screws but I had to protect the hoses from abrasion.

After wandering the aisles of a big box store (and deciding the ready-made nylon bushings cost too much) I ran into stiff walled Pex tubing in the plumbing aisle.


I’ll just cut them to length.

DIY Pool Heater With Pex Tubing Bushings

First, wear eye protection when doing this on the miter saw.

And second, don’t get your hands within 6″ of the blade (or wherever you feel comfortable).

DIY Pool Heater Finished Hoses

So how did I end up with 300′ of kink free hose and have it come out almost EXACTLY right?

Luck and planning. With 8′ square feet of enclosure I figured I would have 2.5sqf per hose or 7.5sqf. So I was pleased it worked out slightly better.

But I’ll take it. And, you don’t need precision as long as the 3rd hose comes out of the enclosure.

Lastly, I left the hoses very loose. They will expand later (kink free hoses do that) and my goal was not to stretch the hoses. But, you can see in the picture some of the hoses came from the factory with stretch.

Hide the Bushings and Lock-in The Hose

DIY Pool Heater Locking Stick

So I didn’t like the white Pex tubing showing, but knew that I would want to lock in the hoses.

After all, I’d have a screwed-on cover and adjusting the hoses would not be an option later.

Using a piece of 1-1/2″ x 1-1/2″ cedar I cut a stick to lay on top of the upper and lower row of bushings.

Then painted it black and using pilot holes screwed it in.

Tip: I noticed the ends so the hose wouldn’t be pinched.

DIY Pool Heater Hose Lock

Step #3 - Installing the Solar Covers on the DIY Pool HEater

DIY Pool Heater Solar Covers

Of all the steps, this is the easist.

But first, a reminder that I chose my enclosure size to fit these. And at about $60 total I wanted them to work.

So, by over-laying the inner edges I had a 25-1/2″ x 50″ wide cover.

These covers install by simply inserting screws into the pre-drilled holes. Since this material can be brittle I didn’t attempt any customization or cuts.

Step #4 - Connecting the Hoses

Intex Pool Pump to Hose Adapter

First, I grabbed three extra 1-1/4″ pool hoses that were 48″ long to allow me to connect into the existing “T”. One hose resumes the connection to the primary pump, the other two are input/output for my old pump.

Easy enough.

But then I spent a good 30 minutes in front of the plumbing bins to assemble what you see above.

A few tricks:

  • The inside diameter (ID) of pool hoses is non-standard at 1-1/4″. 
  • The connection to a garden hose is a 3/4″ male fitting (it doesn’t matter, actually, if it’s male or female fitting). 
  • No, there wasn’t a magic fitting I’ve found (even on Amazon) as this is a completely custom thing to do…post a comment if you find a better way!

With the pieces lined out I used some PVC cleaner and cement (with a screw clamp).

PVC Cement

The assembled hose adapter then looked like this:

DIY Pool Heater Intex Custom Hose Adapter

I am showing one clamp in this picture but later added another for an extra clamp. I also filed off a few ridges that were on the PVC.

Of note, this piece of PVC was made for inside connection not outside. So it was truly custom.

Going full circle, then, the plumbing works like this:

  • I used a 3-year old Intex pump as the “solar pump” to push water through the garden hoses and solar heater
  • This pump was installed at the “T” to the existing pump
  • The output of the solar pump goes through the solar heater
  • A garden hose (cheap, 25′ footer) is dropped back into the pool to close the loop

Best of all, these Intex pool pumps only use a 2-amp motor so I was able to run them side by side.

And by running two pumps I’ll pick up some extra filtration.

Step #5 - Turning on the Solar Heater and Testing it Out

DIY Pool Heater Solar Heated Water Results
Solar Heater Output Temperature

Rome wasn’t built in a day.

And a pool will not heat in a day.

This is all about giving the pool a nudge of extra heat. Due to wind and evaporation I keep a solar cover on at all times (pictured). With a steady flow of warmer water (a SLOW flow, not a gush like your pump output now) I’m hoping to hit 80-82 degrees.

So here’s the initial numbers:

  • Pool temperature: 66.8 degrees 
  • Solar heater output after 30 minutes running: 92.3 degrees (25.5 degree rise!)
  • Air temperature: 73.9 degrees
  • Temperature inside solar dome: 127 degrees 

First, the temperature rise was way beyond what I expected. But, it was the exact mid-day full sun. Later in the day as the sun shifted the output temperature shifted into the mid-80’s. 

And by 9pm it was barely gaining (so I turned it off to avoid a radiator effect of COOLING the pool if on overnight).

Pool Temperature
Pool Temperature
Air Temperature
Air Temperature
Solar Heater Dome Coverage
Dome Temperature

Wrapping it UP

I’ll keep this post updated on results and progress of my DIY pool heater. 

While I don’t expect to take a 68 degree pool to go to 80 degrees soon, I am hoping it goes past 80 over the next few weeks (I max at 78-degrees in a normal summer).

Manufacturer links: Intex

Interesting Finds

Last update on 2020-09-24 at 01:55 / Affiliate links / Images from Amazon Product Advertising API

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