Using grey water to flush toilet

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Using grey water to flush toilet

January 25, 2019, 02:29:06 am

I wanted to pick brains on anyone who has done this or has links to videos/writeups of people who have done this.

Larry, if I remember right you had set this up on one of your rigs.

I am wanting to use grey water to flush the toilet.
I am imaging a "wye" in the water supply,
likely needing check valves (I think that is what they are called - so nothing goes backwards the wrong direction),
a diverter (or something similar) to choose where the toilet water supply is coming from (grey water tank or fresh water tank),
and a pump (to get the water from the grey water into the line and the toilet).

I really want to add an extra grey water tank because we have such a little one in our 89 TK. I figure one for shower to dump into (we use biodegradable soap) and that could be reused for the toilet. The other grey water tank can be used for kitchen sink (and maybe bathroom sink because toothpaste goes down that one).
I am planning on redoing all the plumbing with pex at the same time (just because that is so easy to do in this rig).

Anyone set up their rig to use grey water for toilet flushing?

Any ideas I am missing or any tips to share?

Thanks,
Jane

Re: Using grey water to flush toilet

Reply #1 – January 25, 2019, 02:54:37 am

Ooooo--I like this idea...don't know that I'd tackle it myself, but might ask my guy who repaired my dump valve, if there's a consensus this is doable.

Lynne

Re: Using grey water to flush toilet

Reply #2 – January 25, 2019, 09:41:55 am

This was covered extensively a few years ago on other sites. Most were developed for the users individual operating history. They used an extra water filter and pump to remove gray water and supply the toilet. A back flow preventer would be needed in the fresh water line to prevent fresh water contamination, else the toilet has to be isolated from the fresh water system some how. It all adds weight to the RV, I am pretty limited with a 350 or 35 chassis.

The Red Rover(1990's Class B Roadtrek) owners buried a remote thermometer sensor in the hot water insulation next to the metal heater tank. When the temperature reached 95F or so the turned the hot water heater off and ran only hot water at the faucet, hence no temperature mixing was needed. You will have to change your "turn it off" point based on trial and error. The shower is over when the hot water turns cold(6 or 10 gallons)! I used a inexpensive battery powered thermometer.

We also save water by wiping dirty cookware and dishware with paper towel. We also use three spray bottles of different colors. One with dish detergent and water, one with bleach and water, and one with fresh water. Spray detergent and wipe with a paper towel, then Spray with fresh water and dry.

As far as sterilization, we are sterile to our self to speak.

Re: Using grey water to flush toilet

Reply #3 – January 25, 2019, 06:35:39 pm

Rodney's suggestions are all good ones. I do much the same when showering: an aquarium thermometer with a remote temperature probe inside the water heater's insulating jacket beeps when it reaches a preset temperature (102° F. in my case). I then shut off the water heater and shower using only hot water, which is at the perfect temperature for me. Of course I have to run the water for awhile to get the hot water to the showerhead, but I spray that water into a one-quart Rubbermaid bottle and save it to use when washing dishes, so none is wasted. If you don't count that quart, my shower takes about a gallon of water and about 15-20 minutes of propane use.

Re: Using grey water to flush toilet

Reply #4 – January 26, 2019, 08:00:43 am

Best way to save water while boondocking is don't shower. We bring a supply of baby wipes and you can really get pretty clean by stripping down and wiping up. Once you get somewhere with water though that first real shower really feels good!

Re: Using grey water to flush toilet

Reply #5 – January 26, 2019, 11:42:55 am

Hi Jane; I'm confused about the motivation for using gray water to flush with. In my experience with friends who do that with their home built motorhomes, They do it to preserve fresh water, so as to stay out in the boonies longer. If you use gray water to flush, then you fill up the black water tank faster, and dump frequency is no better. It sounds to me that adding another gray tank would be the solution. Good is that you can pump gray water around into a new tank easily (no 'chunks).
Maybe those 'composting toilet' solutions of venting the moisture outside, could be done with less deleterious effects, using gray water in the extension tank. Or better yet, in the main gray tank; that is already vented to the roof. I could see a fan in the vent on the roof, lil stanker fan - Penelusuran Google
and some type of bubbler providing air into the tank. This would help reduce the liquid volume, and if some form of odor control was used, hopefully not irritate the neighbors. A small amount of biodegradeable tank treatment would help that. A good amount of solar power could provide power for the air supply and vapor exit at the roof. I can just see now a bunch of soap bubbles cascading down the side! Low bubble soap might be necessary. (I remember the mess when a friend put dish soap in a dishwasher!) Hope this helped. RonB

Re: Using grey water to flush toilet

Reply #6 – January 26, 2019, 07:56:32 pm

Ron, yes we are looking to stay out in the boonies longer. We fill our grey tank twice as fast as our black tank - but then our black tank is roughly twice the size of the grey water. Seems a waste of unused space in the black while running out quicker in grey.
Having a second grey tank to bring that from 17 to 30+ gals, combined with our 25 gal black gets us closer to space to put the 50 gal of used fresh water. Being able to use relatively clean shower water for the toilet would make that fresh water last longer.
Jane

Re: Using grey water to flush toilet

Reply #7 – January 26, 2019, 08:13:01 pm

We do water saving methods and do pretty well but I would like to go 2-3 weeks between tank dumps /refills and our tiny grey tank that holds 1/4 of the fresh water tank is our bottle neck.

More extreme measures like no showers is not an option for us - we are talking fulltiming. Creative dishwashing and military showers work well but again our bottleneck is the small grey tank. If I am putting in a second grey tank - makes sense to at the same time. Set it up to reuse some fairly clean grey tank water from the shower to flush the toilet - to make the fresh water last longer.

Re: Using grey water to flush toilet

Reply #8 – January 26, 2019, 08:45:17 pm

Hi Jane, I have a TK also but on a Ford chassis, so maybe they changed the tank sizes. Mine is 18 Gal for black and 24 Gal for gray. Easiest and safest is to just re-plumb the toilet for a pump like this: Camplux 12V Water Pump 35PSI DC 1.2GPM 4.3LPM Diaphragm for Caravan RV... with a screened pick up in the gray tank, electric switch in the bathroom. A tee with shut off would allow you to pump into an extra gray tank, when the main gray tank was getting full.

The drawback is you would need some water in the main gray tank to start with, to flush the toilet, until you built up some gray water reserve. You could use a cup from the bathroom sink (fresh water) to flush the toilet right after dumping. Tank treatments in the gray tank would control smells. I also have 44 gallons of fresh along with the 6 gallons in the water heater. RonB
(edit) Another potential pump, other one a bit too inexpensive..Amazon.com: New RV / Marine 12 Volt DC / 12 V DEMAND Fresh Water Diaphragm...

And a strainer Amazon.com: SHURFLO (255-313) 1/2" Twist-On Pipe Strainer: SHURFLO: Automotive

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Re: Using grey water to flush toilet

Reply #9 – January 27, 2019, 01:14:31 pm

No, I have never suggested or tried to use gray water for flushing.
We do have a transfer pump to move gray water to the black tank, since we always fill the gray tank first.
I see too many potential problems plus having another project to plumb in a secondary pump, more tubing and a new connection to the gray tank.
The water flow holes, around the perimeter of the toilet bowl, are small and could easily plug up with the solids in gray water. Yes, a filter could be installed but it would require periods cleaning, another pleasant job..
Another issue I see is this would offend those with sensitive noses, gray water stinks. My wife would never accept this.
The interior of the rig could get a little ripe at times. No thanks.

Larry

Re: Using grey water to flush toilet

Reply #10 – January 27, 2019, 03:30:29 pm

Ron, yes they seemed to make smarter tank size choices in your TK. We did double check our size early on measuring how much it held and yup we got close to the stated amount.

Larry, I am looking at ONLY using shower water for flushing the toilet. That does not have the smells the sink water has. We use natural soaps/shampoos so they would have little effect on the black tank.
Kitchen sink & probably bathroom sink (has toothpaste, shaving whiskers, etc. in it) would go in a separate grey tank.

Ok, that is what I remembered, you pumping from grey to black tank.

Jane

Re: Using grey water to flush toilet

Reply #11 – January 27, 2019, 04:46:24 pm

Quote from: JandS2 - January 27, 2019, 03:30:29 pm

Ron, yes they seemed to make smarter tank size choices in your TK. We did double check our size early on measuring how much it held and yup we got close to the stated amount.

22' and 23.5' Twin Kings do have undersized hold tanks. There is a lot of room available in the rear, under the lounge, for a large additional holding tank.
If me. I would install the largest tank that fits, plumb it so it works with the existing gray tank and call it good. Install a transfer pump if needed.
To get the shower water from the front of the coach to the rear is going to take a lot of work running 1-1/2' ABS pipe, remembering it needs to have a downhill slope.
BTW, considering that shower water consist of everything that washes off your body, plus soap, it can get ripe too.
It's loaded with various bacteria.

Larry

Re: Using grey water to flush toilet

Reply #12 – January 27, 2019, 05:09:47 pm

Larry, I am sure we have some southern blood in us - you know the women who don't sweat (they have dew on their skin instead). And I am sure they also would never allow bacteria on their skin.

Jane

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Re: Using grey water to flush toilet

Reply #13 – January 27, 2019, 05:33:13 pm

"...we have some southern blood in us - you know the women who don't sweat (they have dew on their skin instead)."
---
"Horses sweat, men perspire, and women glow." Uh huh.

Re: Using grey water to flush toilet

Reply #14 – January 28, 2019, 11:06:29 pm

Joan thanks - Glow was that word I was looking for.
Jane

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Re: Using grey water to flush toilet

Reply #15 – January 29, 2019, 11:49:08 am

I know it seems obvious but sometimes the obvious is overlooked in the quest for complex solutions to a simple problem. We have always carried a collapsible bucket and when boondocking are often able to fill it with water from a nearby stream or even rain water off the roof at times and use that for flushing the toilet.

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