grey water use

[Cary and Don]

Hi,

We are considering using water from the grey tank to flush the toilet.  It seems our grey tank always fills first and using it would make the fresh tank last longer and the grey tank fill a little slower.  We  were thinking of putting a filter and separate pump on the grey tank for the toilet.  Has anyone tried this?

Don and Cary
GMC4107
Neoplan AN340

[white-eagle]

will make the flush smell as bad or worse.  our grey water is definetely bad news, but you're right in that you will save fresh and make the grey last longer.

most folks drip a little grey out on long stays.  keeps the grass green and unless you drip too much, doesn't smell cause it sinks in.  you'd be surprised how much you can drip out each day.

be aware some places don't like drips. 

[redbus]

Re plumb A sink or two into the black tank.

[Lin]

I could see doing what you suggest.  It is true that the grey tank can have its own stench though, so you might need to be adding a bit of bleach or something to it to deal with the problem.

[johns4104]

Thats what they did on the ultra van rvs to save weight and space.

John

[WEC4104]

If it was the bathroom sink or shower only that fed the grey tank, this probably wouldn't be too much of a problem. A little soap and toothpaste mixed into mostly water doesn't seem to bad.  I think the kitchen sink and the tendancy to get residual food from washing dishes is the biggest problem. Decaying food is where you will get the most smell. 

If you add bleach or some other chemicals to the grey tank to kill the nasties, it may prevent that problem, but it will cause you issues when it gets to the black tank.  You actually WANT the stuff in the black tank to be broken down by natural decomposition.  In the black tank, as well as the in an underground septic system,  bleach is going to cause you problems by interrupting the natural breakdown of "the goods".

On many bus holding tank systems (mine included), the grey tanks drains through the black tank.   If I ever get to a point where my grey is full but the black is not, I can always open the grey valve for a few seconds and shift some grey liquid to the black tank.   

[Melbo]

I would think that the "crud" that is in the grey water tank would plug nozzles in toilet and gunk up the flush process. Wouldn't it be easier and keep your inside set up neater to just plumb a pump from the grey to the black tank.  The way mine is set up the grey can be used to flush the black. If the grey water tank level is higher than the black and the valve was opened the pressure would let the grey just flow into the black HOWEVER if the levels evened out the black could flow into the grey which would not be good. Just a thought.

Melbo

[DrivingMissLazy]

I would think that the "crud" that is in the grey water tank would plug nozzles in toilet and gunk up the flush process. Wouldn't it be easier and keep your inside set up neater to just plumb a pump from the grey to the black tank.  The way mine is set up the grey can be used to flush the black. If the grey water tank level is higher than the black and the valve was opened the pressure would let the grey just flow into the black HOWEVER if the levels evened out the black could flow into the grey which would not be good. Just a thought.

Melbo

This is exactly how I drained and flushed mine. I had three valves. One for the Gray, one for the Black and one for the Drain. First open the drain and the black to drain the black. Then close the drain and open the Grey. The black will fill till it is the same level as the Grey. Then close the gray and open the main. Keep doing this and you can get three or four flushed for the black. Finally open all three for the final drain. It works great.

Richard

[Lin]

I think the question was for a way to get double use out of the gray water aside from maximize use of the gray water tank.  I do not believe that creative ways of dumping/cleaning the tank does much to help.  The downside of using chlorine to deodorize the gray water for toilet use seems to be that it will kill the black tank bacteria that you want.  It may also be passing on the chlorine to a septic tank which is another problem.  If you could find some less destructive additive for the gray tank, it still might be doable.  Perhaps some of the RV tank additives would work, but I think the formaldehyde ones would be as bad as chlorine.

[FloridaCliff]

Re plumb A sink or two into the black tank.

Don,

My experience is just like yours, the Gray always fills first.

I have the setup Richard described with the 3 valves, this lets me drain down the Gray into the Black if needed.

Since you are thinking of redoing "something", I like Redbus's thought on the sink drain idea.

I find the Gray water to generally be the most offensive smelling, so an alternative to using it to flush appeals to me.

I guess an experiment is in order and will depend on which one is easier to accomplish and put back if it doesn't work.

Best of Luck and please let us know your results

Cliff

[Linda-XL40-FL]

Ummm... would that filter Cary mentioned be for filtering odors?  Seems to me that using stinky grey water for flushing would allow that odor to fill the coach each time the toilet was flushed.  Just a thought...

[Hartley]

Wasn't there a motorhome or campervan that had the tank drain
into the exhaust system when the engine was running?...

Saw that somewhere a while back...

I think it became illegal somewhere too...

[Nick Badame Refrig/ACC]

Hi Cary,

I like the set-up that WEC4104"Wayne" has suggested. My next bus will have that!

Another way would be to build an overflow PVC pipe from your gray tank, to your black tank.

Good Luck
Nick-

[Len Silva]

Wasn't there a motorhome or campervan that had the tank drain
into the exhaust system when the engine was running?...

Saw that somewhere a while back...

I think it became illegal somewhere too...

It was the Thermasan by Thetford in the 70's, used on GMC's and Airstreams.  Here's a little info:
http://www.gmcgreatlakers.org/GMCGreatLakers/Technical/Livingarea/Thermasan-System/Pages795-800%20from%20X7425.pdf

[JohnEd]

Thanks Len,

Stranger than fiction is fact.

John