Hello,

It is generally accepted that grey water must be used within 24 hours of catchment due to the buildup of bacteria. So, in theory, this timeframe could be extended if the grey water was diluted with fresh water until use. The question is at what ratio and for how long? Has anyone ever considered this approach? I can find no mention of this in my research.

I have an idea that could automatically add harvested rainwater to my grey water at a 1:1 or whatever ration. The goal would be to extend storage time to about three days for my particular irrigation schedule, not to mention ease the concentration of particulates that the filters would have to deal with at one time.


Peace,
Dr. Z.

I'm not sure about the effects of diluting the greywater, but I have an alternative idea. You could build a gravel reed bed in a sealed container, big enough to store 3 days of grey water use. The biology around the roots of the reeds should help eliminate any pathogen problems in the stored greywater, and even if there are pathogens, they would be safely beneath the gravel. You could set up a pump that would empty, or mostly empty the reed bed into your filter and irrigation system, every 3 days or whatever your irrigation cycle is. Better yet, if the elevation makes it possible, set up a siphon so that once the reed bed fills to a certain level it activates the siphon and empties the reed bed without a thought from you. You could adjust the height of this siphon to your greywater output so that the siphon activates every three days.

Zeigh Owensby wrote:Hello,

It is generally accepted that grey water must be used within 24 hours of catchment due to the buildup of bacteria. So, in theory, this timeframe could be extended if the grey water was diluted with fresh water until use. The question is at what ratio and for how long? Has anyone ever considered this approach? I can find no mention of this in my research.

I have an idea that could automatically add harvested rainwater to my grey water at a 1:1 or whatever ration. The goal would be to extend storage time to about three days for my particular irrigation schedule, not to mention ease the concentration of particulates that the filters would have to deal with at one time.


Peace,
Dr. Z.

It seems a poor option to turn high quality drinking water into low grade grey water merely to extend the grey water storage, and I'm not even sure it will have the effect you desire. Grey water doesn't just get a bit nasty, it turns positively toxic as bacteria take over in the tank. You might need as much as 100:1 ratio of clean water to stored grey water.

Better would be to design your system to cope with batch usage of grey water... infiltration pits filled with wood mulch can sink reasonable amounts of grey water quite quickly and make it available for the roots of nearby plants.