Pool Cooling Strategies with Tracking - Fountain, Evening, etc.

DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
Update: As expected, overnight air temp lows were lower this morning, hitting a low of 69F at 6am. It's still 69F at 7:45am. Yesterday evening, around 6pm, the pool water hit 91F, but as the sun began to set it went back to 90F, probably helpful was a very mild breeze that formed. The pool remained 90F when I went to bed.

Upon waking up at 6am, the water temp was at 84, so that was a pretty substantial jump from previous recordings (7 degrees). I ran just the single return fountain for 6 hours and my bowl fountain for 2 hours from 6am and later when temps reached max. Please see the next post for my watering strategy which may lower us some more.

Log (note, I reversed the order from newest to oldest):
06/10 (Previous Day's Air Temps: 100 high, 69 overnight low), Fountain 1230am-730am = Water Temp Differential: 91->84 = 7 degree differential
06/09 (Previous Day's Air Temps: 100 high, 77 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/08 ( Previous Day's Air Temps: 95 high, 74 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/07 (Previous Day's Air Temps: 95 high, 74 overnight low), Daytime pump run, no fountain = Water Temp Differential: 89->86 = 3 degree differential
 
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DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
As my pool is a bit low, I planned to add some water. Following Texas Splash's idea, here's my setup. I measured my water temp (from my kitchen faucet) at 81F, so I assume that's roughly what the water going into the pool is. Possibly it's cooler since the pipes in my home walls are probably warmer than the slab the hose is running through, but who knows.

I have a Flume water meter so I can track how much water I added and will advise the temperature after if it changes. It's supposed to cool to 68 between 8-9am and then raise back up to 72 between 9-10am, charging to 93'ish degrees today. So a couple hours of water at ideal times hopefully helps:

2020-06-10_07-31-44.jpg2020-06-10_07-32-34.jpg2020-06-10_07-33-34.jpg2020-06-10_07-33-52.jpg2020-06-10_07-34-05.jpg
 
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DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
You are beating me to this whole thing. I planned on doing this exact experiment over the summer. I am just about a week or so behind you. So I am watching this intently to see what your results are. Although mine may differ since my pool is about half the volume of yours.

--Jeff
The more the merrier, hopefully we can learn more and track data. If this goes on longer, I may move to a spreadsheet tracking system.
 

DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
Water has been running for 45 minutes, fountains going as well and ran spa spillover to get that cycled in. We're now down to 83 for water temp, outside air temp is 70F and still in the morning shade. Hard to tell which factored into the 1 degree water drop the most, but I'll say the water add probably was the most, but now at 83, or 8 degrees lower than last night's high!

Update 1 at 9am: Shutdown water at 9am, so ran it for 90 minutes. Probably 625-650 gallons put in. Still at 83F water temp. Will monitor today and run again overnight.

Update 2 at 1130am: Didn't take long before it water temp got back to 84F. I'm guessing we'll hit water temps of 88 or 89 by end of day based on previous differential rises. Overnight's forecast shows for a 66F air temp low which is lower temps than last night, so in spirit I can get this thing down even more. The 15 day forecast shows consistent weather and overnight lows in the 60s through this weekend and then staying at 73-74 lows through next weekend. I feel like I can keep this pool under 90 with these measures with the weather we have in June. July and August are going to be a more difficult proposition.
 
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see_feel

Silver Supporter
May 31, 2018
60
Arlington, Texas
If you can get two fountains to run for 8 hours per day, from 12 pm - 8 pm when humidity levels are lower, and spray the water 8-10 ft in the air then you will see a dramatic difference. You are essentially aerating your pool right now. What you need is evaporative cooling. The only way that occurs is by getting the water up into the air and misting. The heat is exchanged in the air and the water that falls back down is much cooler. Because of the volume of water in your pool, this will take around 4-5 days. Once this occurs and you continue this process your pool water reaches equilibrium and the temp will be maintained. Water features do not work for evaporative cooling but they are excellent for aeration. Aeration however does not cool a pool. If you look at your first post in this thread, the fountain you show running is not evaporative cooling, it is aerating. The spray needs to be much higher and misting.
 

DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
If you can get two fountains to run for 8 hours per day, from 12 pm - 8 pm when humidity levels are lower, and spray the water 8-10 ft in the air then you will see a dramatic difference. You are essentially aerating your pool right now. What you need is evaporative cooling. The only way that occurs is by getting the water up into the air and misting. The heat is exchanged in the air and the water that falls back down is much cooler. Because of the volume of water in your pool, this will take around 4-5 days. Once this occurs and you continue this process your pool water reaches equilibrium and the temp will be maintained. Water features do not work for evaporative cooling but they are excellent for aeration. Aeration however does not cool a pool. If you look at your first post in this thread, the fountain you show running is not evaporative cooling, it is aerating. The spray needs to be much higher and misting.
Thanks, yes in my second post you can see a bit more pressure. I'm going to shut off a return and add another one of these gismos which should result in an even higher spray.

I understand the humidity, but I've yet to see a quorum agreement on whether it's better to run these at peak day with in most cases lower humidity and get the evaporative effect or to run them at night and get some evaporative and more actual differential cooling. I agree on the fountain bowls, I've tried them on/off, too early to tell, but I didn't think they'd make a meaningful difference and since they're on a single-speed pump, it's not as cost effective either.

Also, if I cap a return and add another one, I'll be down to one running in-water return. Any issue with me chlorinating through that. Will the chlorinate burn up in this misting evaporation?
 

kazamali

Active member
May 28, 2020
42
Austin, TX
I posted this on another cooling thread, but if you have a high pressure (1000psi) misting system installed, the evaporative cooling effects of that near/over your pool are dramatic (it won't cool the pool, itself, but it creates the "effect"). For anyone building a pool in hot areas, I HIGHLY recommend pre-running conduit/sleeves to various areas of your project so you can later add electrical, plumbing, WHATEVER. At the early stage, it's super cheap and will make incremental updates (like adding a misting system) to your site that much easier.
 

see_feel

Silver Supporter
May 31, 2018
60
Arlington, Texas
Thanks, yes in my second post you can see a bit more pressure. I'm going to shut off a return and add another one of these gismos which should result in an even higher spray.

I understand the humidity, but I've yet to see a quorum agreement on whether it's better to run these at peak day with in most cases lower humidity and get the evaporative effect or to run them at night and get some evaporative and more actual differential cooling. I agree on the fountain bowls, I've tried them on/off, too early to tell, but I didn't think they'd make a meaningful difference and since they're on a single-speed pump, it's not as cost effective either.

Also, if I cap a return and add another one, I'll be down to one running in-water return. Any issue with me chlorinating through that. Will the chlorinate burn up in this misting evaporation?
If you run your pump and thus your evaporative cooling fountains during the day you get the benefit of lower humidity and your cleaning the pool so if guests come over or you want to swim the water is clean. If you run at night only then you will find during the day your surface water is dusty and has junk floating in it. Ask me how I know. :)
 

DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
If you run your pump and thus your evaporative cooling fountains during the day you get the benefit of lower humidity and your cleaning the pool so if guests come over or you want to swim the water is clean. If you run at night only then you will find during the day your surface water is dusty and has junk floating in it. Ask me how I know. :)
Yeah in the new mode, I’m still running 4 hours during the day, typically in the afternoon/evening before and during when we swim. My pool is above trees so it stays relatively clean.
 

DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
Update: It's currently 63F at 7am which is the overnight low. Yesterday, the pool reach a maximum temperature of only 86F. So progress is being made. I was surprised it only got to 86, considering we had 100% sun and still warm weather, only seeing a 2 degree increase was probably a first time for this pool. With the lower starting point and the 63F morning, I saw another 5 degree reduction. It just hit 81, and we have about another 1-2 hours of cool weather pump run time planned. It was 82 at 6am, so I figure 81 will be today's low. We're expecting 94-95 degree weather today and tomorrow mornings lows will rise slightly to 66-67, so today may be the lowest we hit for the season. Not much more to add. It seems the combination of running stuff at night in addition to cooler overnight lows is helping, however, it's hard to not dismiss the significance of the latter.

Average highs in July and August in Austin are 96 and 97 and average lows are 74 and 75 respectively. Without intervention it seems the 86->89 range would be typical based on those averages as seen from the beginning of this exercise. I can live with that, but intervention particularly on evenings with lower overnight lows is going to be a key strategy here.

Log:
06/11 (Previous Day's Air Temps: 93 high, 63 overnight low), Fountain 1230am-730am = Water Temp Differential: 86->81 = 5 degree differential
06/10 (Previous Day's Air Temps: 100 high, 69 overnight low), Fountain 1230am-730am = Water Temp Differential: 91->84 = 7 degree differential
06/09 (Previous Day's Air Temps: 100 high, 77 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/08 ( Previous Day's Air Temps: 95 high, 74 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/07 (Previous Day's Air Temps: 95 high, 74 overnight low), Daytime pump run, no fountain = Water Temp Differential: 89->86 = 3 degree differential
 
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DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
Update: I had a real rough day yesterday. I had a guy tiling my bathroom and then had several loose coping pieces addressed. The latter of which required the team to sand and grind concrete/gunite down to make a smoother area to mortar it back in place. It was a war zone there, plumes of concrete dust ended up in the pool and especially the spa. I had to drain the spa (into the pool), shopvac it and redrain it. Now my Prowler is working overtime on the pool. As a result, I ran pumps all day yesterday. I wasn't getting much success getting the cloudy concrete out. This was a combination of the spring filters in the Prowler (replaced with Ultra Fine) and that pump circulation was working against me. I ran the Prowler over night with no pumps and it was much better, letting the concrete dust collect at the bottom. The pool is looking better, should be perfect in a day. Major filter clean next week is planned. Anyways, as a result, I ran pumps yesterday but not over night. It was 86 degrees in the evening and 81 in the morning with no pumps. I suspect I could've got that extra degree with my strategy. pH has been going like crazy as well (due to concrete), been on top of it, but long story short, it's put a little wrinkle in my testing, so the most recent entry does not include evening pump run time.

Log:
06/12 (Previous Day's Air Temps: 95 high, 64 overnight low), Daytime pump run, no fountain = Water Temp Differential: 86->81 = 5 degree differential
06/11 (Previous Day's Air Temps: 93 high, 63 overnight low), Fountain 1230am-730am = Water Temp Differential: 86->81 = 5 degree differential
06/10 (Previous Day's Air Temps: 100 high, 69 overnight low), Fountain 1230am-730am = Water Temp Differential: 91->84 = 7 degree differential
06/09 (Previous Day's Air Temps: 100 high, 77 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/08 ( Previous Day's Air Temps: 95 high, 74 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/07 (Previous Day's Air Temps: 95 high, 74 overnight low), Daytime pump run, no fountain = Water Temp Differential: 89->86 = 3 degree differential

Images of the pool situation, this is after I made substantial progress yesterday:
Screen Shot 2020-06-12 at 8.20.31 AM.pngScreen Shot 2020-06-12 at 8.20.21 AM.png

and this was after I drained the spa:
Screen Shot 2020-06-12 at 8.22.04 AM.png
 

DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
Update: I spent a lot of time cleaning the pool up, I'm basically done and can resume normalcy. Last night I ran at very low pump speeds as I wanted the robot to do more work on the bottom, so I had only minor fountain action. Also, last evening we went into the pool, water temp only hit 86 and cooled to 85 around sunset. My wife actually felt it too cold. As air temps went from the low 90s into the high 80s, the wife bolted. I'd say 88 is the perfect temperature, but I enjoyed the cool down effects of 86. I'm also adding a few hundred gallons now.

With the consistency of weather now, I may go back to my old daytime schedule and see if I maintain 5 degree differentials or if it goes back to 3-4 just in the effort of science.

Log:
06/13 (Previous Day's Air Temps: 93 high, 68 overnight low), Fountain 8pm-730am (Low Speed) = Water Temp Differential: 86->81 = 5 degree differential
06/12 (Previous Day's Air Temps: 95 high, 64 overnight low), Daytime pump run, no fountain = Water Temp Differential: 86->81 = 5 degree differential
06/11 (Previous Day's Air Temps: 93 high, 63 overnight low), Fountain 1230am-730am = Water Temp Differential: 86->81 = 5 degree differential
06/10 (Previous Day's Air Temps: 100 high, 69 overnight low), Fountain 1230am-730am = Water Temp Differential: 91->84 = 7 degree differential
06/09 (Previous Day's Air Temps: 100 high, 77 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/08 ( Previous Day's Air Temps: 95 high, 74 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/07 (Previous Day's Air Temps: 95 high, 74 overnight low), Daytime pump run, no fountain = Water Temp Differential: 89->86 = 3 degree differential
 

JamesR

Gold Supporter
May 18, 2015
127
Nazareth/PA
Cracks me up that you folks think 86 degrees water temp is cool. 😀. Mine hit 84 yesterday and we call that warm!! I went in the ocean last week on the jersey shore with my grandson and it was 62 degrees. Now THAT is cold.
.....still admiring the pool build you have there. That was one heck of a creative project!!! I would have looked at that sloping back yard and said: “ Nope, sorry honey no pool in this yard”. You really pulled it off.
 

DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
Update: Given my wife saying it was too cold last night, I opted to not run anything overnight. When I first turned the pumps on, it reported 82, but after about 30 minutes of morning pump time it fell to 81. I do think I can get an extra degree of cooling if I run overnight versus daytime.

Log:
06/14 (Previous Day's Air Temps: 94 high, 67 overnight low), Daytime pump run, no fountain = Water Temp Differential: 86->81 = 5 degree differential
06/13 (Previous Day's Air Temps: 93 high, 68 overnight low), Fountain 8pm-730am (Low Speed) = Water Temp Differential: 86->81 = 5 degree differential
06/12 (Previous Day's Air Temps: 95 high, 64 overnight low), Daytime pump run, no fountain = Water Temp Differential: 86->81 = 5 degree differential
06/11 (Previous Day's Air Temps: 93 high, 63 overnight low), Fountain 1230am-730am = Water Temp Differential: 86->81 = 5 degree differential
06/10 (Previous Day's Air Temps: 100 high, 69 overnight low), Fountain 1230am-730am = Water Temp Differential: 91->84 = 7 degree differential
06/09 (Previous Day's Air Temps: 100 high, 77 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/08 ( Previous Day's Air Temps: 95 high, 74 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/07 (Previous Day's Air Temps: 95 high, 74 overnight low), Daytime pump run, no fountain = Water Temp Differential: 89->86 = 3 degree differential
 
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DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
Sorry, no update today. Regrettably, I had an incident with a skunk in close range and that has really messed my day up. By time I got to the pool, it was quite warm. I hit 86F water temp yesterday, and it's not 3pm and already back to 86F. It's not as hot today as yesterday, but again not running overnight is showing a trend of warming the pool. I'll continue the log tomorrow.
 

DB-Cooper

Well-known member
Jun 18, 2019
303
Austin, TX
Update: 06/15 was a loss due to the aforementioned skunk attack. Water temp got to 86F yesterday evening. By nightfall, water temp was down to 85F. We also had a small storm roll through providing some evening cooling. However, it brought significant humidity, and overnight lows were fairly high. We only got down to 75F briefly, but most of the evening it hovered around 77F with higher than normal humidity. Despite running the pumps and fountain overnight, starting with 85F water temp, I only was at 84F by morning. However, after running through the morning, by 8am I had hit 83F. It didn't take long for it to get right back to 84F.

So what this shows is that getting into the 60s or even low 70s has a high cooling effect. Additionally, it seems the humidity also hurt a bit, but I need a larger sample. Previous nights that had 77F overnight lows were also starting with higher water temps. Needless to say, I only got barely a 3F water drop overnight.

Log:
06/16(Previous Day's Air Temps: 94 high, 76 overnight low), Fountain 8pm-730am (Low Speed) = Water Temp Differential: 86->83 = 3 degree differential
06/15 (Previous Day's Air Temps: 94 high, 69 overnight low), Didn't measure due to skunk incident
06/14 (Previous Day's Air Temps: 94 high, 67 overnight low), Daytime pump run, no fountain = Water Temp Differential: 86->81 = 5 degree differential
06/13 (Previous Day's Air Temps: 93 high, 68 overnight low), Fountain 8pm-730am (Low Speed) = Water Temp Differential: 86->81 = 5 degree differential
06/12 (Previous Day's Air Temps: 95 high, 64 overnight low), Daytime pump run, no fountain = Water Temp Differential: 86->81 = 5 degree differential
06/11 (Previous Day's Air Temps: 93 high, 63 overnight low), Fountain 1230am-730am = Water Temp Differential: 86->81 = 5 degree differential
06/10 (Previous Day's Air Temps: 100 high, 69 overnight low), Fountain 1230am-730am = Water Temp Differential: 91->84 = 7 degree differential
06/09 (Previous Day's Air Temps: 100 high, 77 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/08 ( Previous Day's Air Temps: 95 high, 74 overnight low), Fountain 1230am-730am = Water Temp Differential: 90->86 = 4 degree differential
06/07 (Previous Day's Air Temps: 95 high, 74 overnight low), Daytime pump run, no fountain = Water Temp Differential: 89->86 = 3 degree differential