Cooling water thoughts, Good idea or wishful thinking

[Mobile785]

We live in GA and our pool water tends to get into the low to mid 90's this time of year. I've been look all over this forum as well as other internet sites to find a way to cool the water. The best that everyone comes up with is to run the pump at night with a fountain. While that does work kinda ok, usually dropping the temp a few degrees overnight, I was talking with a friend and we came up with an idea and wanted to run it by people here and see if this would work.

Has anyone tried geothermal to cool thier pool? I have access to a ditchwitch to dig 8 or so feet down where the ground temp is in the 60's. So what we were thinking is getting 100' coil of 1 1/2" poly pipe, dig a ditch 8' deep by 20' -25' or so long and expanding the coil in there and then filling it back in. Then use a jandy valve as a bypass, in one position water would come out of the pump and straight back into the pool, when cooling is not needed. In the other it would be diverted to go through the undergound coil for geo-cooling before returning to the pool. We figure cost for the coil and PVC and joints needed to compete this project would run around $250 maybe a little higher.

I know $250+ seams a little high for cooling considering I could get a fountain for a fraction of that but by doing it this way theres no increase in evaporation like with the fountain. Its easier to start cooling, once installed, no monkeying with the returns to hook up the fountain just rotate the jandy.

So is this just wishful thinking or are we on to something?

Jimmy

 

[George N]

Interesting idea but wouldn't the water stagnate in the pipe when its not being circulated for a while?

 

[JohnT]

I'd think you are short on pipe. Household geothermal uses hundreds of feet of tubing, and the task of changing water temperature requires a lot more heat movement than changing air temperature does.

 

[Mobile785]

Interesting idea but wouldn't the water stagnate in the pipe when its not being circulated for a while?

See this is why I asked here I would think that it wouldn't as it would be underground in a closed system where no air could get to it not to mention no sun to burn off the chlorine that's in it. But I could be wrong.

If I am wrong and I most likely am, I guess I could always move the Jandy a tiny bit to allow bare very minimal flow through the pipe to avoid stagnation.

 

[anonapersona]

My pool is always cool in the deep end. The waterfall pump pulls from the deep end and although the first few minutes of waterfall run time is warm water due to the hot waterfall rocks, after a few minutes the water is cool. I do not know how long it would take to fully empty the cool waters of the deep end nor how fast that area would chill again.

I recall once locating a soil temperature vs depth chart that IIRC quoted a near constant 55 degrees in winter in central Miss. at 3' depth, I was not looking at the summer temps but it was not a whole lot warmer, guessing maybe 65, but one ought to try to locate that data. Someone has done the work on that. Anyhow the point is that you probably don't have to go too very deep to get a decent amount of cooling. However, flow rate and volume of water may be quite important. Also the act of pumping can add heat and you have frictional losses to overcome. I am too far removed from all that to be of any real help at this point, however. And I worry about leaks far underground, which could be devastating.

 

[swimcmp]

Had a customer that was going to heat and cool his pool with geothermal. After the estimates came from the heat/ac companies he decided it was to expensive. What I have been told is water is tough to heat and cool and takes a larger system than say air for a house.

 

[imrodee]

I have a house in NY that has radiant heat - The coils in the concrete slab are filled with water and sealed. Its the same water that's been in the coils since the house was built in the 50's. The gas furnace is the size of a stove. It seems that someone could figure out how to use that set up as a cooling system and build it in the gunite. hmmmm. :idea: