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Bug512 01-07-2013 07:06 AM

Gray water to flush toilet ?
So I am looking into making a system (pump, valves and filter) to use our gray water to flush the toilet.

Anyone here know of anyone who made a system to do this?

pumper9x9 01-07-2013 07:32 AM

Interesting idea, but you may have to clean the toilet more often, it will smell like gray water, and you'll need to leave some amount of gray water in the tank or put some in it for it to work. If your intent is just to save room in your gray water tank so the black water tank is close to full when the gray water is you might try washing and rinsing dishes in a tub and then dump that down the toilet, collecting the shower water that you run to get the water hot in the same tub and use it to wash the dishes. Or install a system to transfer some gray water to the black tank. Unless you do a lot of boon docking this might not be worth the effort. Also if you do a lot of boon docking you might consider a sun shower and take your showers outside. You might also consider getting one of those portable dump tanks. The more complicated you make the systems the more stuff there is to screw up and break. There are probably a bunch of unintended consequences that will be discovered after you set the system up.
Good Luck

RickO 01-07-2013 07:47 AM

I've never heard of it being done but it sounds like a GREAT idea to me!

Good luck with it.


Ed-Sommers 01-07-2013 09:16 AM

That is not an unknown resource in the Boondocking world but I know of no "plans" for doing so but remember that a few discussions (I know not where), recommended the source of the gray water be up off the bottom, and if bleach is in the gray water, it is not appropriate for the black tank because it kills the bacterial action going on in there which is important for boondocking, and fulltime, but not a factor for weekender's.


JohnBoyToo 01-07-2013 09:26 AM

Novel idea,
would save fresh water for use elsewhere
but I wonder if there is a law against connecting black water to grey water?
(which (via piping) is connected to fresh water)

You'd have to have some valves and pumps for sure.... Have to think on this a while...

others have tried it:

Recycle Bathwater to Flush Toilet - YouTube

Bug512 01-07-2013 09:54 AM

Here is my reason. We boondock (at music festivals) or have limited hookups when we camp and conserve as mush freshwater as we can. It's painful to see nice clean freshwater being used to flush the toilet. This also give a little more room in the gray tank also.

So my idea is to draw gray water from the holding tank and use a demand water pump just like the freshwater tank uses. I think a filter before the pump would be a good idea to protect the pumps and valves on the toilet from particles that are suspended in the gray water.

I would bring the feed line into the toilet room and have a series of quick connects to "unplug" the freshwater from the toilet and then connect the gray water line. I would not rely on any three way valve as a means of isolating the gray water flush line to the fresh water system.

Or I could use a three way valve and put a check valve in the freshwater line. that would be to means of a stop.

So the process begins.

Thanks for everyones input.

Sky_Boss 01-07-2013 10:51 AM

I think it could be a good idea with a few assumptions.

1. We found that in our Winnebago with 51 gal black and 53 gal grey that we would have to dump the grey tank 2-3 times as often as the black. (We tested this out in our CG for future reference.)

2. If one chose to use CG toilet facilities to some extent then I would think one could make a significant increase of time between dump by channeling grey water to the black tank.

3. The big caution would be on having full fresh water and full waste tanks with the associated weight until dumping could be done. I once had full water and 1/2 black & grey tanks and exactly maxed out my rear axle on the gasser. :banghead:

These thoughts assume that the reason to conserve water is more based on camping without sewer hook ups or boondocking instead of hyper water conservation beliefs.

I don't know about any sidebar issues relating to the affects on grey water on black tank odors and such. That could cause other issues.

MRBB 01-07-2013 10:52 AM

If you have 2 grey tanks and use the shower tank this would work but you don't want to use the kitchen sink tank. The grease will stink more than the black tank and clog up the valves and leave a nasty ring in the toilet along with a very bad smell.

TdogKing 01-07-2013 01:10 PM

Sounds like a good idea to me . I don't think it would all that hard to do. Like you said the biggest problem is keeping gray water particles from plugging your pump. We don't and never have put grease down our kitchen sink . Even if you had to wipe down the toilet here and there its not the end of the world and paper towels are easy to dispose of. I would come up with a system that pulls grey water from a couple inches off the floor of the grey tank and most likely you might not have clogging problems. Keep us posted .

vsheetz 01-07-2013 02:14 PM

How about a rainwater collection system - use this to flush.

fastcat 01-07-2013 02:18 PM

My wife would not tolerate the smell and the extra cleaning. Maybe yours is more forgiving. :thumb:

Traps90 01-07-2013 03:34 PM


Originally Posted by fastcat (Post 1423318)
My wife would not tolerate the smell and the extra cleaning. Maybe yours is more forgiving. :thumb:

My wife would kill me if I tried that:banghead:. She's good for 2 maybe 3 nites boondocking and then back to FHU's:D

TdogKing 01-07-2013 03:38 PM

Are you telling me your grey water smells worse than what you leave in the toilet ??? There is no smell of nothing once you push the pedal and flush...At least in my Motorhome anyway .

ChooChooMan7 01-07-2013 03:47 PM

I would think about an aquarium sand filter. Just my 2 cents.

I have seen setups like this on the net. It is a great idea.

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