Pool Temp Comparision - Can't Figure it out.


Active member
Jun 3, 2020
Fargo, ND
Ok - Trying to figure something out here - Need some input. Both my neighbor and I have 18' above ground pools. Mine is a 52", his is a 48" - so we're talking what - like 600 gallons difference between the two. Today - which was a 92ish degree day, my neighbors pool was about 87 degrees. Mine, by comparision was 81. We both have almost identical blue solar covers. Our pools are located not even 100 feet away from each other. I even have a 4x4 solar heater running all day long.

I cannot for the life of me figure out why this temperature difference exists. His pool has no heater at all - it's one of the wicker liner frame coleman pools. I have an Intex XTR frame pool. He bought a hayward pump / sand filter, I have the intex crystal clear sand filter / pump.

Now - I'm not upset about this difference at all - my 81 degree pool was wonderful today. But I cannot figure this out! I know there could be a ton of variables, I just want to know!

Here is what might be more relevant information to help:
My pool is just about 1/2 setup next to the deck. The part that's open to the yard is West / North West.
I excavated the ground to make the top of the pool line up with the deck. My neighbors sits on the lawn as is.
Both our pools receive the same amount of full sun all day long.
I've also included a bunch of pictures that might spark something.

Our current leading theory is that because my neighbor runs his pump each hour for a certain amount of time, we think that might be stirring up the pool allowing the water to warm more evenly where as the top 3-5 inches of mine is VERY warm all day, but colder below that? I run my pump from about 9pm - 2am. Idk - help lol!

Neighbors pool on the left, mine below right (image from last week) My property line bordering the walkling path is facing west.

Better shot of my pool / deck - facing north.

Neighbors pool closer up
123456.jpgMy solar 4x4 solar heater (1" poly, taco pump, clear twinwall polycarbonate)



Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
You measuring the temperature of both pools with the same thermometer?

Your neighbors pool is shielded by the fence and gets less wind and evaporation. Evaporation is what causes most of the temperature loss. I think your pool is more exposed to winds.

There is enough thermal load in the amount of water that once the temperature diverges between the pools the cooler one is not going to catch up without a heater.



Well-known member
Jun 16, 2019
For starters the cheapo pool thermometers are +/- a few degrees. His is +2 and yours is -2 and you’ll barely ever tell the difference between 83/85 on the thermometer. Even with a digital meat thermometer or equivalent, different spots of the pool can be a bit off.

then factor in the above points (both spot on) and the reflection from his PVC fence. When the sun hits fencing or vinyl siding the right way it can be 10 degrees warmer in the area nearby.


TFP Guide
I know you said you run the pump 9p-2a but do you run it during the day as well? Running some during the day will help mix hot and cooler water and not have a super hot layer on top.
You mentioned a solar panel and solar heating doesn’t work at night. It actually becomes a cooling radiator at night if you’re pumping water through the solar panel.
More ground contact would help keep the pool cooler.
Do you leave the cover on at different times?


Bronze Supporter
Sep 19, 2019
Phoenix Arizona
Your solar panel is doing more cooling than anything if you’re running water through it at night. You need to run the pump during the day for any chance at warming the water.


Active member
Jun 3, 2020
Fargo, ND
Ok - replying to everyone:

Yes, temps were checked with the same thermometer.

I should mention my solar heater runs on a separate loop, a taco floor heat pump hooked up to a timer running 11am to 6pm.

I also thought about the ground contact / cooler air under the deck thing - as of now and until I get a steel sided pool the sides do not actually come in contact with the ground.

Interesting ideas about the fence / wind / reflection stuff though.

We do keep our covers on mostly the same times as well.