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Help needed with recycling greywater to flush the toilet! Answered

We have a small shower and toilet room and what I'd like to do is use the water from the shower and store it in a tank so that it can be used for flushing the toilet. It sounds simple enough, but I'm new to building things like this so I have a few questions to ask the forum! 1. I've read that greywater can go stagnant quite quickly. Would this matter if it was only being used to flush the toilet? If it is a problem, is there a simple/compact/cheap way of filtering the water first? 2. You'd need to make sure that there was always enough water in the tank to flush the toilet, so there would need to a minimum amount in there that if there wasn't enough greywater from the shower available, that it would get topped up from the mains water. Would you use a float valve for this or is there a better way? 3. I'm not exactly sure where I would be able to position the tank. Either way I would probably have to use a pump of some sort, either to get the greywater into the tank or to get the water from the tank to the toilet. Should I just use a submersible pump or something else? Any other ideas or small projects that people have done would be great to hear about. Thanks James


I am also involved in designing a cheap, self made and aesthetically integrated system. There is a man in Spain who did it in a very basic (but effective) way and shares his experience in the web:
Good luck!

i dont think there is problem

you need somehow to prefer the grey water over fresh water

i'd connect the fresh water thru manual valve - you ope it intentionally if there is no enough water

if you can define for a machine when the system should fill with fresh water we'll be more on the way. if its just when there is no enough greywater it'll near always be filled with fresh water

water from the shower (containing hair etc) is hard on the pump. itll clog most pumps after single or few uses. you need some filter that you'll have to maintain all the time

brutal design pumps (like archimeds screw or chain of cups) stand that much better but take lots of space

maybe its easier to move the tank manually after bathing (its not that much of water)

Thank you for your thoughts. Glad to hear you think that the stagnant water wouldn't be a problem. With your answer to 2 though, I'd really like to have the system completely automated if I can? Any ideas? Like you say I'll have to have a decent filtration system to remove all the hairs etc. ! Thank you J

ok i see how to automate its decisions in the main storage tank (~ 0.1 M3 or larger) there is red line at the bottom. the amount of water below the line is sufficient to one flush of the toilet (~ 0.005 M3) the tank fills directly with grey water and stays full above the red line all of the time the clean water supply is activated when the water level comes below the red line in this system its possible to have problems of stagnant water cause the water realy changes rarely. to avoid the problems use an tank with open top and place it outside exposed to sunlight (directly - not thru glass). sunlight cures water and can slow down to a crawl the processes that kill the water once in some time (2 weeks ?) wash the tank walls from inside with a hose the clean water supply should be placed above the max possible level of water in the tank and fill it from above. only the float itself is under the water at the bottom (connected on a long vertical stick). this way water from the tank cannot leak into the clean water system when pressure in the clean system drops connect an overfill pipe to the top of the tank. connect its other end to another reservoir of grey water. if you have so much of it you sure would wnt to use it for watering the gaden etc as well. or you can discard extra grey water you still need to get the water somehow from under the bath to over the toilet. a pump will likely clog fast. a filter will protect the pump but clog itself fast. brutal devices like arcimedes screw can withstand such water and require less fine filter only to prevent it from clogging the valves in the toilet tank

I've got a schoolbus that's been converted to a camper. I've been thinking about the greywater issue. If you could flush with grey, and replenish the bowl with a secondary spout of fresh it would be good. I want to be as conservative with my water as possible, but stagnant greywater sounds questionable.