I get what you mean about mesh covers—tried one on my old rain barrel and it just became a mosquito hotel after a few weeks.
Funny, I saw those shade balls at a municipal reservoir once and thought they looked ridiculous, but if it works, it works. Personally, I’m still a bit skeptical about the snap-on lids for bigger tanks—mine warped in the sun after a summer, but maybe I just went cheap. Curious if anyone’s had luck with DIY rigid covers that actually last?“For algae, I tried a floating shade ball setup—looks weird but cuts down on sunlight big time.”
Rigid covers for rainwater tanks are a bit of a rabbit hole, honestly. Here’s what I’ve seen work (and not work) over the years:
- UV-resistant polycarbonate sheets: These hold up way better than most snap-on lids, especially if you reinforce them with some aluminum angle. Downside is they’re pricier and need decent support across the span or they’ll sag.
- Marine plywood sealed with epoxy: Not the prettiest, but if you seal every edge and hit it with a good exterior paint, it’ll last several seasons. Needs re-coating every couple years though, and can get heavy on bigger tanks.
- Corrugated metal roofing panels: Surprisingly effective if you frame them out right. They reflect heat, don’t warp, and you can hinge them for access. Just watch for sharp edges and rust if you’re in a humid spot.
Snap-on plastic lids almost always warp unless they’re specifically rated for outdoor/UV exposure. Most of the cheap ones are just thin HDPE that goes soft in the sun.
One thing I’ve noticed—no matter what cover you use, if there’s even a tiny gap, mosquitoes will find it. I started using weatherstripping around the rim and that cut down on bugs big time.
Curious—has anyone tried those retractable pool covers on a rain tank? Seems like overkill but maybe there’s a scaled-down version that works for smaller setups. Or maybe I’m just overthinking it...
Also, for anyone doing greywater recycling—are you running into similar algae or mosquito issues, or is that less of a problem since the tanks are usually opaque?
Retractable pool covers on a rain tank—now there’s an idea I hadn’t even considered. I get what you mean about it maybe being overkill, but the convenience factor is tempting. I wonder if you could DIY something similar with those heavy-duty outdoor tarps and a pulley system, instead of springing for a full-on pool cover setup. Has anyone tried something like that, or would the tarp just end up sagging and collecting water on top?
On the greywater side, I’ve been curious about that too. Our greywater barrel is a solid blue plastic, so it doesn’t let in much light, and I haven’t seen any algae yet. But I’m not sure if that’s just luck or if the lack of sunlight really makes that much difference. Does anyone know if the temperature inside those opaque tanks gets high enough to cause other issues, like smells or bacteria? Or is it really just the light that’s the main problem for algae?
Tried the tarp-and-pulley trick over a rain tank once—let’s just say it turned into a backyard waterbed after the first storm. Unless you’ve got a way to keep it taut, you’ll be out there bailing puddles every time it rains.
On greywater: Light’s the main algae culprit, but heat can definitely make things funky. Opaque tanks help, but if your barrel sits in full sun all day, you might notice some smells or even a bit of slime. I’ve found parking mine in the shade keeps things pretty chill... literally and figuratively.
Title: Green Plumbing Showdown: Greywater Recycling vs Rainwater Harvesting
That tarp-and-pulley setup sounds like a classic case of “good in theory, tricky in practice.” I’ve seen a few folks try to rig something similar, and unless you’re using some serious tensioning (think ratchet straps or even a frame), it’s almost impossible to keep the water from pooling. Once that happens, you’re right—might as well call it a kiddie pool. Honestly, sometimes the simplest solution is just a solid, fitted cover.
You nailed it on the greywater too. Light’s the big algae driver, but heat’s no joke either. I’ve had tanks go from fine to funky in a single hot week. Opaque tanks are a must, but even then, if they’re baking in the sun all day, you’ll get that swampy smell creeping in. Shade makes a huge difference. I’ve even seen people build little lean-tos or toss old pallets up for shade—doesn’t have to be fancy.
One thing I’d add: if you’re stuck with a sunny spot, a bit of insulation around the tank can help keep temps down. Nothing high-tech, just some foam board or even old blankets wrapped around the sides. Not perfect, but it slows down the heat gain.
It’s easy to get discouraged when these setups don’t work out right away, but honestly, most of us have had at least one backyard experiment go sideways. Trial and error’s just part of the deal. You’re definitely on the right track thinking about light and heat—those are the big ones for keeping water clean and usable.
