Keeping the Water Warm

[CoffeeBean]

I have a 32 x 16 AG pool and live in western PA. When we installed it the surrounding trees were much smaller than they are now. Hence, the sun no longer shines on the pool for as many hours a day to warm the water. It hovers in the 70s unless I turn the heater on which is a bit chilly for me even on hot days.

We contemplated trying solar but the only location we could use is too far away from the pool's equipment and access "eyes" and there would be a whole lot of exposed, ugly piping to get there.

We have a gas heater but at $400+ a month to maintain 82 degrees I could join the local Y and swim in their over chlorinated pool all year but would rather not.

We have an Aqua Shield safety cover on it which precludes the convenient use of bubble wrap if I turn the heater on to get it up to comfortable water temp. Can't use a roller because of the shield and there's not enough deck room to just ball it up in between uses. (I lift the panels & prop them up to use the pool if I have company. Otherwise I just open the end panels so I can get in & out, and clean the filter.)

Our pool is totally surrounded by a deck. We can crawl entirely around the pool under it. We were wondering if an application of that foamy insulation onto the outer pool wall would work to keep the water temp warmer for longer periods?

Has anyone tried something like this? OR - does someone have some other solution that might work?

All suggestions welcomed.

[PoolDoc]

I don't have a clear sense of the temperature profiles you are encountering. Are you saying it "hovers" in the 70's in July and August? or May and September? What are average highs and lows for each month?

Insulation will help . . . IF night time lows are BELOW 75 degrees or so. BUT, you have to be concerned about trapping moisture between the foam and the pool wall, or even IN the foam, and causing accelerated corrosion. Unless you keep the walls and foam DRY, even using the spray-on foam could be a problem.

On the other hand, solar may be more of an option than you think.

Say you set up a solar panel layout that can deliver a 20 degree rise (75 to 95) 80' from your pool. You could run (2) 3/4" PEX lines INSIDE a 2" S-40 PVC line, and bury it just under the surface. Careful fitting selection can keep pressure loss below 5 psi for flows of 2 GPM. 2 GPM with a 20 degree rise works out to about a 20,000 BTUH heating rate. (2gal x 60min/hr x 8.3 lbs/gal x 20 deg delta = 19,920 BTUH).

You'd need a commercial type circulator pump, like this stainless steel Taco pump, on an independent loop, NOT connected to the pool pump . . . but you might have to make sure you run BOTH the circulator AND the pool pump, so you could take off the solar loop DOWNSTREAM of the filter. Otherwise, you might end up with clogged pipes or panels.

Doing all this wouldn't be cheap; probably at least $1,000. But once it was in place, it could operate for less than $10/month.

I think you'd have to buy a single panel, first, and install it quick and dirty, so you could test your volume and temperature delta. That's the only way I know to RELIABLY verify everything will work properly BEFORE you lay out some significant dollars.

[CoffeeBean]

Wow. Thanks for the detailed reply!

Let me see if I can be more precise about the water. Since the trees are so high now (and there's no way to top all of them to let in more sunlight) the pool water rarely gets above 76 degrees F even when our ambient temps are in the 80s and 90s as they were here this summer. If I turn on the burner and set at 83 it'll get there but within a couple of days it's back down to the 70s.

I see what you're saying about getting moisture in between the foam and the pool walls. I really hadn't considered that angle. We also tossed around the idea of a wrapper, sort of like the one you put on your hot water heater but 1) I don't think one exists that large and 2) unwrapped insulation would be a nightmare when it got wet and 3) since you mentioned moisture I'm sure this idea would also result in it as well. Oh well.

As for the solar idea. There are a couple of your comments I need you to explain. Thank you by the way for assuming I'd understand it all. :-)

You said "You could run (2) 3/4" PEX lines INSIDE a 2" S-40 PVC line, and bury it just under the surface." What are PEX lines and the surface of?? The ground? If so, why do I need to bury it? To avoid heat loss?

The only place that gets enough sun would be our garage roof. The pool pump is about 40 ft from the garage edge. From the ground to the roof top is about another 50 feet. Would the commercial pump be able to move it those distances?

From everything you wrote I'm fairly sure setting this up is beyond my expertise. Would a solar installation company know how to do something like this for a pool?

Thanks again for your input.

[PoolDoc]

1. Search HomeDepot for "PEX tubing". (or Google)

2. You don't have to bury the line, but I assumed it might be running across lawn, and that you'd prefer not to leave it exposed.

3. The circulator could NOT perform the initial lift. Once the lines were FILLED, it could handle the circulation. But if an air lock occurred, you'd have to replicate the startup. To lift 40', you need 25 psi. That's a design problem what would require special consideration. Many AG pumps won't reliably generate 25 psi.

4. Could solar contractors do it? No, not as a rule. Or, yes, but only with a massively oversized and inefficient pump. I probably shouldn't have mentioned it -- I know how to do it, because (a) I was a plumber, (b) I've done controls and energy management work, (c) I have a good practical knowledge of circulatory hydraulics, (d) I have a degree in engineering management (abt 3/4 of a full engineering degree) and remember a fair bit of it. That's an uncommon combination.

'Techy' DIY types, who are willing to do a LOT of leg work, and are able to do the trial-and-error could succeed. But finding a contractor to do it? Not really.

But, you could ask. There ARE some very sharp pool guys out there; they are just the exception, rather than the rule. But you might be lucky, and find one.

Sorry for the problem.