black and gray combined

[Globie64]

We're contemplating replacing our black tank, which we've been using as a gray tank with a composting toilet. We don't really have the room for a separate gray tank, and we're thinking we may go to a conventional toilet (someone else isn't entirely thrilled with the way the composter looks. sigh) Some new Airstreams combine gray and black tanks, and I thought, why not? I'm curious to get feedback from others on this. The separation made sense in the past when you could, as my owner's manual suggests, dig a hole at your campsite and put a hose into it for your gray water disposal. This isn't cool anymore, at least most places. Thanks

[RickDavis]

Worst thing you could do in my opinion. As long as black (brown?) and grey are seperate there are ways to dispose of gray water if boondocking or parked on grass. The stuff has a tendency to disappear during the hours of darkness.
That option is gone as soon as you combine tanks.

[Belegedhel]

I hadn't heard that any modern trailer is built with a combination black and grey tank. I can think of a few reasons why you would not want to combine them:

1) You are exposing all of your grey-water plumbing to the black water in the combined tank. I can easily imaging the contamination making its way back to your kitchen sink, the floor of your shower, etc., in no time at all. If you manage to overfill the tank, ie., draining your kitchen sink into a "full" tank, well now you have all of the contaminated overflow of the tank in your shower pan.

2) A grey tank is typically going to fill faster than a black tank. If you are not connected to a dump, if the two tanks are separate, you at least have the option of sneaking a hose into the bushes and releasing some grey water. You take this option completely away if the grey and black are combined.

3) When you dump your tanks the process is typically to dump the black first, then the grey. This allows you to get at least a partial rinse of the stinky slinky using your grey water. Combine the tanks, and this capability goes away.

So what do you mean that there is no room for a grey tank? Vintage Trailer Supply makes a tank that is low and flat and designed to mount below the subfloor, but above the belly pan. Yes, it is more work to plumb than having a tank inside the living compartment, but you certainly won't be the first to go through it. Right now, I am using a Thetford Curve Porta-potty as a temporary toilet (because my trailer is torn all apart and not replumbed yet). I can put ~5 gallons of water in the top of it, and the "tank" in the base holds 5 gallons. This is enough for two people for a weekend--maybe its a way to go on a temporary basis.

[Protagonist]

The main reason, in my opinion, for keeping separate black and gray tanks is capacity. You might be able to install a combined tank the size of your former gray tank, but you'll be hard-pressed to install one with the same total capacity as you would have with separate black and gray tanks.

By the way, if you have a combined tank, it's not a gray-and-black tank; it's just a black tank. Blackwater is any water containing human waste, and any tank that contains blackwater is by definition a blackwater tank, even if blackwater is only a tiny fraction of the tank's total contents.

[TBRich]

Originally Posted by Belegedhel

I hadn't heard that any modern trailer is built with a combination black and grey tank.....>snip<....

Newer 16' Bambis have a single holding tank that combines black and grey.

[mandolindave]

I don't have a grey tank, but I can configure the grey to back up into the black tank. I forget the exact method because I don't ever do it. As I am trying to remember, it occurs to me that I would get very dirty hands while dumping, because it must involve capping off the dump outlet, and opening up the black water valve. I could use a refresher course on this exercise.

An off topic word or two about grey water. Grey water is a combination of fresh water and food that you could have put in your mouth, and water and soap that was on your person. Not so bad, but leave it sit in a tank for any length of time, and whoa...it gets really nasty. A honey dipper truck had a mishap and dumped about ten gallons of grey water on my campsite. I would have bet pink slips that it was black water. I went off on the guy. He said not to worry. He splashed some fresh water on the spill, and 20 minutes later there was no evidence of the mishap. The microorganisms in the soil, made short work of neutralizing the nasties.

I know it is uncool to dump grey water in public areas. I never let food stuffs go down my drain, and when camping in my woods and meadows, I let the grey water go on the ground right away. I never notice a puddle or odor.
I let the dogs do their business an my lawn, wash my car outside, and have a composting pile. So I personally don't have a problem with grey water going on my property.

[andreasduess]

I don't have a problem with dumping grey for as long all soaps and detergents used are 100% biodegradable. We tend to use Dr. Brommers soap for everything, people, dishes, floors.

There are places I would not dump grey, like for example desert environments.

We will be combining our grey and black next year, when we'll be installing a composting toilet.

[Ramble On]

The 2004 International 28 footer has a 70 gallon combined tank. Works fine for my camping style.

[TG Twinkie]

I have a small (12 gal) grey water tank in my trailer. I did not want to tear the thing apart to install a larger tank. I was able to fit a 21 gallon tank under one of the twin beds. I tied the drain pipe from the new tank in to the galley sink drain pipe. The drain line for the new tank has a ball valve. When closed the tank will not drain. When it comes time to drain it, open the valve and the GW runs in to the original GW tank. Of course one would have drained the original tank first, then leave the dump valve open and drain the new tank. When both tanks are empty, close the dump valve (original tank) and the ball valve on the new tank.
One would ask. How do I fill the new GW tank? I have a Valtera dump valve with a cap that has a hose fitting. I put the Valtera dump valve on the sewer outlet, then attach a hose, which is connected to a pump in the trunk. The pump discharge is hard piped to the new GW tank. Turn on the pump (3gpm) it takes about 5 minutes to empty the contents of the original GW tank into the new tank.
Now I have 33 gallons of GW capacity. Dealing with the Valtera valve and hose to the pump is much easier than dealing with a portable tote.
I have a friend who used my idea on his trailer. Which had no GW tank. He simply installs an end cap on the sewer outlet. Turns on the pump when showering. The GW is pumped into the tank. When the tank is full, he switches a series of valves, then runs the pump to empty the GW tank.
These are options to consider. An alternative to tearing the coach apart.

[mandolindave]

Any castile soap for that matter. I can't always find Brommers. I will say that my favorite peppermint " flavor " can be a little bit overwhelming on certain body parts. ( did I say that out loud?)

The government did a study ( yeah I know ) because they wanted to know what happened to the rubber that wore off the millions of vehicles. They determined that the rubber didn't get much more than five feet away from the highway before microorganisms broke it down.

A university did a study on outhouses, and found that the effluent didn't get more that a few inches away from the pit before it was neutralized.

The chemical companies are saying the same about pesticides and herbicides. ( I don't take chances believing that. They also said that Agent Orange was safe if used correctly)

I don't know what to believe but that we all can make a big difference, doing our little bit.

[Globie64]

We currently use the old black water tank for gray water: but the cap on the dump outlet and open the dump valve, and the gray water backs up into the tank. We're using a composting toilet, so there is no "black" for the black tank. Our tank is already under the floor, above the belly pan, so it's not like we have an above floor tank and we can add one below floor. I was also cautioned about adding weight behind the axle. The points about not mixing are all duly noted and I totally get it. A suggestion was made about using a blue, wheeled tank. Dumping gray water isn't so cool- bathing water can have pathogens in it, and food waste etc can turn nasty pretty fast. For actual septic systems, the rule of thumb is 8' before pathogens are removed.

[Belegedhel]

"We currently use the old black water tank for gray water: but the cap on the dump outlet and open the dump valve, and the gray water backs up into the tank. We're using a composting toilet, so there is no "black" for the black tank. Our tank is already under the floor, above the belly pan, so it's not like we have an above floor tank and we can add one below floor."

Ah, perhaps the solution is becoming easier: Continue using your existing below-the-floor black tank as a grey water tank. Now, is there a way you could place a new black tank on top the subfloor, and mount a lower profile toilet on top of that? This is roughly how it was done in my '73 GT. Your challenge following this strategy would be plumbing the dump valve assembly. If you are worried about too much weight too far behind the axle, then I would suggest dropping the bellypan, installing a grey tank or two in the below-floor bays immediately behind (or even coincident with) the axle, and then you can go back to using your existing black tank where it is.

[Globie64]

I had had that thought, put a gray tank somewhere ahead of the axle, between the frame members. Since gray water shouldn't be lumpy, it could be plumbed rearward in maybe 1 1/4 ABS to a wye and some kind of valve at the dump valve- currently, ours is in the center under the rear bumper, but it could be moved. What's a reasonable gray water tank size? I do kinda like the low profile toilet with the above the floor black tank, although the toilet is at the very rear of the trailer and that puts all that extra weight out there.