Painting the barrel black is a solid move—blocking sunlight is key. I did something similar, but instead of paint, I wrapped mine in reflective insulation. It kept algae down and didn't heat the water nearly as much as I thought it would. Might be worth a shot if you're worried about overheating. Either way, good call tackling algae head-on...it's a pain once it gets established.
I've thought about reflective insulation too, but wasn't sure if the cost justified it for me. Instead, I ended up using some leftover landscaping fabric around mine—kept algae manageable, but probably not as effective for temperature control. Curious though, has anyone compared algae growth between greywater systems and rain barrels? Wondering if the nutrient levels in greywater make algae worse or better...might influence which system I expand with next year.
I've noticed my greywater barrels definitely get algae quicker than my rain barrels. Probably the soap residues feeding it... Rainwater stays clearer longer, at least for me. Not a huge difference, but noticeable enough to factor into planning next year's setup.
Interesting observation about the algae issue. I've actually found the opposite in my setup—my greywater barrels tend to stay clearer longer, surprisingly enough. Could be because I use soaps specifically labeled as biodegradable and low-phosphate, which might limit algae growth. Also, my rain barrels are exposed to more direct sunlight, which definitely encourages algae blooms.
Have you considered the placement of your barrels? Even a bit of shade can drastically reduce algae growth. Another thing worth checking is whether your greywater system has enough filtration before it hits the barrel—sometimes even a simple mesh or gravel filter can make a noticeable difference in water clarity.
Not saying your experience isn't valid, just that there might be other factors at play besides soap residue alone...
"Even a bit of shade can drastically reduce algae growth."
Good point about shade—I noticed something similar when I moved my rain barrels under a tree. Algae growth dropped noticeably, but then I had to deal with leaves and debris clogging things up. Have you had any issues with debris buildup in your greywater filters? I'm thinking of adding a gravel filter myself, but I'm curious if maintenance becomes a hassle over time...
