How to insulate pool at night

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LaugherNYC

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Sep 25, 2016
3
Bedford/NY
I want to squeeze a couple more weeks of pool use out of the Fall, with below-average temps. Unfortunately, I was not advised to install a retractable cover when they built the pool 20 years ago, and the cost to rip up the coping, install guides and a well, and put in the cover is ridiculous.

However, to keep the pool warm enough to do my PT (88-90 degrees) in it every day for an hour, I could easily burn through 400 gallons of propane a week!

I tried a solar cover, but the thing required four men to put on and off - the pool is 18x54, and if water gets on top of the cover, forget it. I returned it. So, I just bought a couple of 20x30 4 mil waterproof silver and black tarps, and laid the across the pool. I have no idea if that's going to provide any insulation and prevent heat loss at night. Any opinions??

I guess I could just leave the heat off one night and see what temp the pool drops to, but I have noticed that it's a bad idea to let the gunite cool down once it's up to temperature in the summer -- it's better to keep the pool warm, and if it drops to 75 overnight, I'm gonna have to heat the concrete back up to 88 along with the water!

Does anyone think a 4 mil plastic tarp like that will be helpful? It seems to me it has to reduce evaporation. I don't see any steam coming off of it in the morning!
 
The water temperature is going to mainly be affected by evaporative heat loss as that carries away the largest amount of heat energy (latent heat of vaporization for water is huge). So, I think your covers will help a lot as long as they are kept in place. Keep the pool covered until you use it and then cover it up right away afterwards. Unfortunately you're battling mother nature and the laws of physics so you will eventually lose. But you might get a few more weeks out of it as long as you wallet can handle the propane expense....
 
Solar cover with reel is the best answer. If the pool is 18x54 rectangular then I would suggest one reel at each end with a 18x27 cover. One person can reel up both of the covers in a few minutes with no strain. Replacing them takes a bit longer. If two people are available it's easiest with one in the pool and the other at the reel. To keep a pool heated as the weather cools requires either keeping it covered at all times (when not in use) or a lot of energy (AKA $$$).

BTW It seems to make little difference if the solar cover is the lightest, cheapest one available or a thicker more expensive one.
 
With two people (my wife and I) working, I anchor one end of the first tarp to the corners of the pool and walk it down towards the middle, holding the leading edge up. Since it overlaps the coping, no water gets on top. I then anchor the leading edges at the corners. We then open up and slide the second tarp over the first, and overlay it over the coping at the far end. No problem, no sinking, and with just six ground spikes, it stays in place, with the tarps lying on the surface of the pool, and the edges overlapping the coping. As long as the edges in the middle are pulled tight so they don't slump into the water, they stay up no problem. It's a good, tight seal, and the skimmers even work fine because the tarps angle up off the water leaving a space for the water to flow into them.
 
LaugherNYC said:
With two people (my wife and I) working, I anchor one end of the first tarp to the corners of the pool and walk it down towards the middle, holding the leading edge up. Since it overlaps the coping, no water gets on top. I then anchor the leading edges at the corners. We then open up and slide the second tarp over the first, and overlay it over the coping at the far end. No problem, no sinking, and with just six ground spikes, it stays in place, with the tarps lying on the surface of the pool, and the edges overlapping the coping. As long as the edges in the middle are pulled tight so they don't slump into the water, they stay up no problem. It's a good, tight seal, and the skimmers even work fine because the tarps angle up off the water leaving a space for the water to flow into them.
Click to expand...
That sounds clever. As long as your attachment system works, and as long as wind and/or rain don't cause you grief (I'd have some worries about that, with only six ground spikes), you seem to be achieving the main goal of preventing evaporative cooling. Having an approach that works fairly easily for you means that you are more likely to actually cover the pool whenever you are done using it.

Please keep us updated as to how well this works out for you over the next several weeks.
 
WOW!! I was thinking about the burner all night, as it got down to 44 degrees here last night. When I got down to look at the pool (It's blocked from the house by a row of evergreens), I was annoyed to see one corner had slipped off, and maybe 30 sq feet of the surface was exposed. Well, at 5:45, I went down to do my swim and PT, got the covers off myself in less than 5 minutes (I didn't bother folding them, since I knew they were going back on), and had a wonderful swim in 91 degree water BEFORE I went to look a the gauge of the tank -- I didn't want to spoil my swim with the thoughts of $100 bills incinerated in the chilly air. Well, from 9 AM Sunday to 6:45 PM Monday, I burned less than 5% of the tank, which is 400 gallons. That means about 20 gallons, at $2.45 or so, or around $50 for 36 hours! That's a HUGE savings over the normal burn last year when I shut the heater off after it went through 400 gallons in under 3 days, and it wasn't this cold, in mid-Sept. I will happily spend $50 a day to get my hour and my wife's 30 minutes of swimming in on these beautiful fall afternoons in our yard. I would happily waste $100 a day for three weeks of swimming here, rather than going to pay for a therapist for an hour 3 or 4x a week, $450-600 a week to do bands and resistance PT in a gym, and always ache afterwards instead of almost pain-free swimming.

I would say the savings is 80-90%. At the 36 hour burn rate, a tank will last me 30 days or more, while it would last 2-3 days uncovered. That's PHENOMENAL.

The tarps cost me a total of $150, and the ground pegs $15, and the rope to use to pull the tarps from the other side of the pool $8. All in $173. And I can use the tarps to cover a bunch of stuff in my garage over the winter:).

I compare that to the $1500 for a thermal blanket, plus a reel or such, and I'm happy. The solar covers might be a good investment, but only if I did two, as suggested, because they are absolutely impossible to manage in one piece - they sink and weigh a ton!
 
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