Reverse Osmosis waste water recycling

June 10, 2019 8:16 AM

We have a reverse osmosis (RO) system in our house. RO systems waste a lot of water—I think I’ve read it’s 2 or even 3 gallons of waste for every gallon of filtered water. Our waste water just goes into a sink in our basement—rather than directly into a water pipe—so we could harvest it. We’re not going to drink it—salts and solids would be off the charts. Would the plants mind? What else can we do with this water?

Our town has very mineral laden water, and in addition to tasting bad, it’s out of spec for our refrigerator ice maker and our espresso machine. We’re definitely going to continue using the RO system.

But we want to use the waste water for something. Is it safe for plants? For animals? I’d estimate that the TDS are about 160 ppm.

posted by Admiral Haddock to Home & Garden (4 answers total)

It’s not clear if you use RO for the whole house (toilets, showers, etc.) or only the taps. The RO waste water is still usable for irrigation, washing, and multiple other uses. See this brochure from the Alliance for Water Efficiency.
posted by sudogeek at 8:48 AM on June 10, 2019

We collect ours into 5 gallon buckets in the utility sink and use it to presoak laundry. This allows us to use less detergent overall.
posted by waving at 8:59 AM on June 10, 2019

You could use it to flush toilets, either by dumping it into the bowl (in most toilets that will cause the bowl to empty), or using it to fill the top tank (you will have to disable the automatic fill mechanism somehow in that case).
posted by exogenous at 2:25 PM on June 10, 2019 [1 favorite]

If it's really only 160ppm that is acceptable for many plants, just not lime haters or sensitive plants like orchids. How much does it rain where you live? Here we get more than enough rain in the non-summer months that salt accumulation in the soil is not an issue but if you live in a very dry area that might be different.
posted by atrazine at 3:38 AM on June 11, 2019