With the kind of heating you folks are talking about, I assume you’re wanting to swim all year round.

If all you want to do is start swimming earlier in the season and stretch the season a few more weeks, do this:

Get some ¾” pvc pipe and 90deg elbows, and make as many 4’x4’ squares as the surface of your pool will take.
Cover the squares with heavy duty black landscape plastic sheeting (We found it in 4‘ wide rolls). We made 8 of them for less than $50.00
When you’re not in the pool, float the black squares in it.
If your pool gets any direct sun light, you’ll be amazed at how much these cheap (aka: Red-Neck Pool Heaters) will heat the water.

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1980 300D - Veggie Burner !