Turning Your Bathroom Wastewater into Garden Gold

I set up something similar last summer and it's been working pretty well. Your sand-gravel-charcoal idea is solid, but I'd suggest adding a simple settling tank before the filter layers. It catches hair, soap scum, and other gunk that could clog things up quickly. Learned that one the hard way... Also, make sure you're using biodegradable soaps and shampoos - plants aren't fans of harsh chemicals. Overall though, totally worth it - my garden's never looked better and my water bill dropped noticeably.

Sand, gravel, and charcoal may catch some debris, but that setup doesn’t disinfect greywater or establish that it’s safe for irrigation. Requirements and suitable uses vary locally, so check your local greywater rules and use an approved system; keep irrigation practices appropriate for the water and plants rather than spraying it onto edible parts. A filter alone isn’t a safety guarantee.

What’s in the garden, and would the water be delivered at soil level or by spraying? For example, a setup aimed only at suitable ornamental plants is a different fit from one watering edible crops; the destination and delivery method matter as much as the filter choice.

If edible crops shared the garden with suitable ornamentals, I’d keep the greywater on a separate outlet to the ornamental area rather than send it to the crops; whether any edible-crop use is appropriate depends on the delivery method and local rules. A dedicated outlet or diversion could help separate those destinations; the filter choice doesn’t solve that issue.