I know they make solar covers for pools, but I that is a bit of a pain to put on and take off all the time and my cover (from a well known manufacturer) from last year was easy to rip and became brittle and fell apart in a few thousand pieces at the end of the summer.

I was thinking about taking milk jugs, pouring a bit of black paint in them to coat the inside, letting them dry, and then submerging them in the pool. This sounds like it would be more effort than the solar cover, but I don't think I would need to remove them every time. Also, they could double as weights to keep the normal cover on when it storms.

Are there any DIY solutions that work well to really warm up a pool?

I live in Ohio, USA if that matters/helps.

  • With your current requirment need to find out how big is the pool and how many jugs you are planning to use. You many required 1/3rd the area size with respect to pool area. Than there may be a chance under good sun light. May 29, 2013 at 8:28
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    If you put actively decaying nuclear waste in those jugs your pool would warm up. May 29, 2013 at 16:05

5 Answers 5


As others have said milk jugs are too small and much of your heat loss is due to evaporation.

An alternative would be to build these "lily-pad-pool-warmers".

They are basically hoola hoops with black plastic sheeting stretched across them. You make a bunch of them and then float them on the pool. How much good they do will depend on how much of the surface they cover.

  • Accepting this answer because my question (not what the title was changed too) was for DIY ways to warm up a swimming pool. Upvoted the other answers that were helpful. Jun 3, 2013 at 11:12
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    I figured I would post back on here. I made the "lily pads". I ended up having to use a soldering iron to join the black plastic to the hoola hoops. Glue didn't work nor did a laundry iron. Jun 19, 2013 at 19:58
  • Both the black plastic and the hula hoops are probably polyethylene, a kind of greasy plastic that very few glues will stick to, but which will heat weld together quite nicely. Jul 14, 2015 at 15:24

I'm not clear on how some milk jugs are going to heat the pool. Most of the light will have scattered before it reaches the submerged jugs. Plus the surface area is going to be minuscule compared to the pool area, unless you have thousands of jugs.

Finally, I thought one of the main benefits to a pool cover was to reduce evaporative heat loss. Underwater jugs won't help you at all.


Submerging black milk jugs is not going to create any worthwhile difference. The overwhelming source of heat loss in an outdoor pool is due to evaporation. Evaporation literally draws heat out of the pool. You need a solar cover to stop the evaporation.

Compare your pool against a lake, with water stratification. From the surface, looking below it is pretty much black, indicating that all of the incoming sunlight is being absorbed. Despite that, if you dive down several feet, you'll find the water temperature gets very cold very fast, even if the upper layer of the water is warm.

If absorbing all sunlight isn't enough to warm the whole of a lake, it certainly won't be enough to heat your pool with several black milk jugs.


Nobody has discussed the displacement issue.

By filling up a pool with milk cartons (full enough to sink to the bottom) a lot of water would be pushed out when the jugs are placed in the pool, and will then require additional cold water from the water supply to be introduced to bring the water to the proper level, lowering the temperature even further.

Looks like the solar cover is the best solution, of course it depends on the depth of your pool as to the interval for placing and removing the cover.

  • That really depends on how far from the top of the pool the water level is. :) Dec 16, 2014 at 21:27
  • Not a problem, if you don't mind swimming in a pool of black jugs.
    – Tester101
    Jan 6, 2015 at 16:07

Throw black trash bags on the surface of your pool.

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