When To Run The Filter For A Warm Pool

[Nolte919]

My wife and I are having a disagreement. We have a 12 foot diameter, 2.5 feet deep above ground pool with a blue solar cover. I think it will make the water warmer to run the pump during the warmest part of the day. My theory is that by circulating cooler water up to the top it will do a better job of warming up the entire pool. Once the top layer of water gets warm the sunlight hitting it will be less effective and that warm top part will radiate off more heat and the wind will do a better job of cooling it off if the top is warm.

My wife feels we should run the pump in the evening or at night so the water can be still during the hottest part of the day and get nice and warm at the top. It's hard to convince her otherwise since the water certainly feels warmer her way.

So I'd love to hear some opinions one way or the other.

Thanks.

[waterbear]

My wife and I are having a disagreement. We have a 12 foot diameter, 2.5 feet deep above ground pool with a blue solar cover. I think it will make the water warmer to run the pump during the warmest part of the day. My theory is that by circulating cooler water up to the top it will do a better job of warming up the entire pool. Once the top layer of water gets warm the sunlight hitting it will be less effective and that warm top part will radiate off more heat and the wind will do a better job of cooling it off if the top is warm.

My wife feels we should run the pump in the evening or at night so the water can be still during the hottest part of the day and get nice and warm at the top. It's hard to convince her otherwise since the water certainly feels warmer her way.

So I'd love to hear some opinions one way or the other.

Thanks.

Evaporation is the main cause of heat loss in a pool, and solar cover really work by preventing evaporation, so that being said:

1) keep the pool covered and the pump off at night when evaporation is going to have the most impact on heat loss. If you run the pump at night there will be more evaporation than if the water is still.

2) uncover the pool and run the pump during the day. an uncovered pool will heat up faster than one with a blue cover.

[chem geek]

(I wrote this as waterbear was writing so some duplicate info here.)

In terms of the overall average water temperature in the pool, she is wrong and you are right about circulating during the day and not at night. You can heat the pool even faster during the day if you remove the cover, assuming that your humidity isn't very low and that you don't have a lot of wind since those factors would increase evaporation which would cool the pool counteracting the heating by the sun. In a white plaster pool, 60% of the sun's energy is absorbed by the water; in a darker pool, it's more than 90% including that absorbed by the darker pool surfaces.

Now you need to decide which is more important to you -- marital harmony or being right.

[quantumchromodynamics]

You should consider getting a solar panel to help warm the pool if you have somewhere convenient to mount it.

[PaulR]

This spring when we started getting serious sun again, one day I noticed the temp at the surface was a very pleasant mid-80s; this is with the pump off. However, elbow deep to take a water sample, it was a different story, I forget exactly but on the order of 15 degrees cooler.

The stock advice about solar panels is you want the water coming out only 1-2 degrees warmer than it goes in, to maximize efficiency. The reasoning is similar for solar covers, circulation during sunlight hours gets you the most benefit.

--paulr