We have a solar cover for our pool. It’s essentially a big, plastic sheet of bubble-wrap that sits on the pool surface. To remove it, we crank it onto a big reel — it’s pretty much a necessity to have a reel for these things, particularly with a large pool like ours.

After 5 seasons of dealing with solar covers, I’ve learned quite a bit about them. Contrary to what one might initially think, they don’t increase heating during the day when the pool is exposed to sun. In fact, they actually reduce daytime heating by blocking sunlight. There’s a bit of a greenhouse effect that heats the top foot or so of water, but the rest of the water sees less sun so doesn’t heat up as much. One desirable side effect of this is that it reduces chlorine usage during the day. So.. if you’re going on vacation and want to cut down on chlorine demand, put the cover on.

The biggest benefit of a solar cover is that it reduces heat loss and evaporation at night. So for the warmest water, you want to cover the pool in the evening and uncover it during the day.

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The drawbacks of solar covers are subtle and a bit paradoxical (hence the title of this post). The biggie: You’d think that using a solar blanket to cover a pool would keep the pool cleaner, but it doesn’t. In fact, you could argue that it actually makes the pool dirtier. It’s true that when the pool is covered, stuff will fall on the cover instead of into the water. And sure, you can even use a leaf rake to clear the larger debris off the cover before you remove the cover. But when it rains, the dirty and untreated rainwater will collect around the folds and creases of the cover, and then when you remove the cover, the dirty water (along with whatever debris is still there) all falls into the pool and fouls the clean water. Then, because most of the debris is already waterlogged, it immediately sinks down to the bottom of the pool. Contrast this to when the pool is uncovered: the skimmers collect all the debris before it sinks, and the rainwater immediately mixes with the treated water rather than puddling up on the cover.

Solar covers (like any cover) also encourage neglect of the pool. When the pool is covered, I find myself more likely to skip chores like adding chemicals, brushing, emptying skimmer baskets, running the automatic cleaner, etc. When you combine this with rain and extra organic debris, it can lead to an algae bloom pretty quickly.

Conclusions: Unlike conventional covers, these things really are not meant to keep stuff out of the pool. Use them only for their thermal properties (chilly nights etc), and keep them off during the day and in particular, when it rains. If you must use the cover when it’s raining to conserve heat, uncover the pool as soon as possible after the rain stops.

I’ve often thought about getting a leaf net cover to keep out debris. I think it would complement the solar cover nicely, and in certain instances the two could be used at the same time. I hesitate because I’m not sure how much trouble it would be to put on and take off, and how I would anchor it down to keep it from blowing away, falling in the pool, etc. When you think about it, another tradeoff with covers in general is that they are an impediment to getting in the pool. It’s much easier to go swimming when the pool is uncovered and ready to go. No one wants to spend time fumbling with a big, unwieldy cover beforehand. Still, in the late summer and early fall, when we’re swimming less frequently anyhow, the leaf net may be worth the hassle.

Better late than never, we took our first swim of the season today. It’s nice to finally be using the pool, because it makes the hassle of maintaining it seem more worthwhile. It’s not quite worth all the effort and expense IMHO, but still, it is nice to be able to hop in the pool on a hot day. And when it’s not full of leaves and other assorted crap, it’s nice to look at too.

I got a pleasant surprise when I uncovered the pool this morning.. the algae clinging to the diagonal hopper walls was almost totally gone. So, it appears that repeated brushing and superchlorination is the ticket to getting rid of this stuff. Apparently I don’t need a steel-bristled brush after all (although it may hasten the process, so I may pick one up anyhow). In future years, I’ll try to be a little more faithful with the off-season chlorination so the algae won’t take hold like it did this year.

Also, I made a test cut in the pool deck with my new diamond blade. And I must say, it cuts very easily — much more easily than I expected. As I suspected, the circular saw doesn’t cut quite deep enough. However, I can now go ahead and rent a larger concrete saw with the confidence that it’ll do the job. The current plan is to take a day off this week (work schedule permitting) and do it. Still not quite sure how I’ll do the curved sections. I’ll figure something out I hope.

Yesterday we finally uncovered the big concrete hole in the backyard. The water looks pretty good, but due to my neglect over the spring, I’ve got a bigger problem with surface-clinging algae than in past years. There was the usual green stuff on the bottom which easily vacuumed out, but the steps and the diagonal hopper walls have this better-established stuff that doesn’t want to come off. However, the stuff on the steps cleared right up when I flooded it with 12.5% hypochlorite from my siphon hose, so I superchlorinated yesterday evening. This morning I noticed that the areas I had brushed yesterday were clearing up, so I went ahead and brushed the entire pool (clouding it up beautifully, of course). Cl was 8.8ppm. Tonight I’ll add more, until all the muck is gone.

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Still haven’t started the coping repair project. Today (Friday) I picked up a 7″ dry-cut diamond blade for a cool $50, and I’m going to see how it does at cutting the concrete decking. It’s not big enough to cut through the entire slab, but the hope is I can make a cut around 2″ deep and then knock the rest of the piece off with a cold chisel. If it works well, I’ll go ahead and rent a larger saw to do the complete job. Whether it works or not, I’ll still end up with a nice diamond blade I can use for future projects.

The fun never ends..

6/12: The crap clinging to the diagonal hopper walls is proving to be very tenacious. It will not brush off easily in spite of repeated superchlorination. I can’t seem to get enough force on my brush to attack it effectively. I think I’m going to need a stainless steel brush for this. Before I try that, though, I’m going to try flooding the area with chlorine. It worked with the steps, so hopefully it’ll work with the hopper walls. Only problem is, I could reach the steps easily with my siphon tube, but not so with the hopper walls. So, I’m going to try a slightly different approach. I went to Home Depot and bought 20′ of food-grade tubing (1/2″ O.D.). I’ll use wire ties to attach 4′ or 5′ of hose to the bottom of my telepole, then put the pole in the water and start a siphon. I should then be able to siphon chlorine from my jug and direct the flow wherever I want. I will probably want to do this with the pool pump off, and somehow attach the tubing to the chlorine jug so I don’t inadvertently pull it out. We’ll see how it works.

6/14: Tried the above last night. It works, but it’s a little cumbersome. Attaching the siphon tube to the chlorine jug is an absolute must. I used an Irwin Quick-Grip clamp. Still, I lost my siphon and had to re-prime several times. It would also be handy to have some way to easily interrupt the flow while I move the hose to different spots. I suppose it would work to pinch the hose, or I could use a spring-loaded clamp. Still, this whole thing seems like too much hassle compared to using a steel-bristled brush, assuming the brush will work. I’ll try to get to a pool store and pick up a brush in the next couple of days.

I’m already thinking about next year’s pool project, and I haven’t even started this year’s yet…

For next year, I’m considering adding an automatic chlorine feed using a chemical metering pump, similar to the setup described here. The main goals of the project would be:

• Save work;
• Save money on chlorine by matching the supply more closely with the demand;
• Provide a continuous feed of sanitizer, thereby eliminating the need for cyanuric acid in the pool.

If I go ahead with this, I’ll probably also move the pool’s electrical controls indoors, which I’ve always wanted to do for convenience more than anything else. I’d also need to run a dedicated 110VAC circuit to power the metering pump, so while I’m at it, I’ll install a convenience outlet near the pool equipment. Right now, I only have 220VAC there.

The metering pump can be had from Grainger for around $300, but I’m watching eBay to see if I can get a new one cheaper.

I’ll add random notes to this entry as I think about this one.

Yesterday was supposed to be the big pool-uncovering day, but it didn’t happen. The original plan was to open it early so I could get my coping project underway. But, yesterday it occurred to me that I could get started with the cover still on, and just pull the cover back to expose whatever area I happen to be working on. At that point it became a no-brainer: Leave the cover on for now and avoid the hassle of keeping the pool clean in late May when no one is using it.

I already had my help on the way over, so instead of uncovering the pool, we tackled the time-consuming job of scraping the old caulk out of the coping expansion joint. This was fairly easy to do with box-cutter type utility knives and plenty of sharp blades. However, on the decking side, it left a bit of residue because of the roughness of the concrete. I may try wirebrushing this area to get the last bit of caulk out.

Next up is to rent the big concrete saw and cut a true expansion joint (removing the caulk revealed that, as I expected, the joint is non-true around the entire perimeter of the pool). My current plan is to take a day off work and do it the week after Memorial Day. I’d like to get it done before my Vancouver trip; otherwise it’ll have to wait until June 10 at the earliest. Come to think of it, I suppose there’s nothing stopping me from doing it this week, either.. To deal with the dust, I’ll try duct-taping a tarp to the coping edge. With the cover still on, it’ll support the tarp and keep it from submerging. It might work.

I did my first water test yesterday, and surprisingly the numbers weren’t too bad: Free Cl 1.4, Combined Cl 0.2, pH 7.7, Alk 80, Hardness 170, CYA under 30. Water temperature was 63°. I’ll probably add some chlorine today.