Why not grey water into black tank?

pilgrim_still · 06-28-2003, 05:10 PM

I've been wandering in a dangerous place -- inside my head. I am repairing/remodeling a 1973, 31', SLY, rear bath. I have the rear bumper off and the underbelly skin off to fully expose the black water tank. Repairs to the supports are underway. And, I am waiting for a replacement dump valve. This vintage trailer does not have a grey water tank. All the dish/sink/bath water is directed into the dump pipe just aft of the dump valve.

Why can't I put a valve on the grey water line to divert it into the black water tank? A "Y" connector/valve would allow grey water into the black tank if, for example, we are stopped on the roadside for lunch and want to wash up. Otherwise, it seems the water goes on the ground! Untidy.

As long as all the sinks have water traps I shouldn't get any sewer gas odor. Right?

What am I missing?

**jcanavera** · 06-28-2003, 05:35 PM

Quote:

Originally posted by pilgrim_still
As long as all the sinks have water traps I shouldn't get any sewer gas odor. Right?

What am I missing?

Because you are combining the two systems into one tank, your tank will fill faster. If you overfill the tank, the backup will probably come out your shower drain. Of course you now have sewage in the shower.

Jack

overlander64 · 06-28-2003, 06:30 PM

Greetings Jim F!

What you are suggesting "backing grey water into blackwater tank" is something for which instructions exist in the owner's manual (at least for mid 1960s coaches). It does, as Jack suggests, greatly shorten the time between trips to the dump station. It is also another reason to always be sure to have a tight fitting rubber plug in the bathtub drain. The basic process suggested in the owner's manual is:

1.) Place a blank (no hose connector) termination cap on the dump valve.

2.) Open blackwater tank gate valave. (You now have the setting to back-up the gray water into the blackwater tank).

The time when it gets a bit unpleasant is when dumping:

1.) Before dumping, close the blackwater tank gate valve.

2.) Place bucket under the termination cap (Be sure to wear gloves) and remove termination valve - - be prepared because there will be sewage trapped between the termination cap and the gate valve.

3.) Attach your usual sewer hose and continue with the normal blackwater tank dump routine.

This process only works if the blackwater tank is mounted below the floor which elimates the possibility for trailer that like my Minuet have the blackwater tank mounted above the floor - - it does work with my Overlander where the tank is mounted below the floor.

Kevin

Chas · 06-28-2003, 07:58 PM

My former 2000 year model slide-in truck camper had a single waste tank which held both the black and grey water. Never had any problems with it backing up but could see that if it ever did it could get pretty nasty in the shower. I have never been so far off the path that I was able to fill up the black tank on any RV, the grey yes, but not the black. So the thought of having them both combined really makes sense to me. I guess they did it to save space and it held quite a bit, 30 gallons or so.

I can tell you that it held much more grey water than my Overlander, mine is a 74, the first year for the grey tanks and they hold barely 10 gallons of grey water, almost useless. A blue tank is a must have item!

Chas

RoadKingMoe · 06-28-2003, 08:11 PM

Why not? Simply because for the average RVer, you dump the grey tank 3 times as often as a similarly sized black tank. Get a blue tote tank the same size as your black tank and you'll dump it twice before needing to dump it and the black tank. Much better than having human stool on your feet in the bottom of your shower.

**Pick** · 06-28-2003, 08:19 PM

One more thing to consider on that '73. If it has the same black tank as my '72, the capacity is not that great. Once, when mine registered 1/2 on the control panel, I dumped it into the "blue tank". Not much went in, about 8 gallons or so. So, I estimate the black tank to only hold 18-20 gallons, allowing for the shape of the tank and accuracy of the level gauges.

DanT · 06-29-2003, 06:16 AM

All,
Being new I hesitate to post but having a plumbing background I figured I might as well. The original reason for seperate tanks was grey water was produced more and it was considered safe to dump anywhere.

It used (50s, 60s, 70s) to be ok to dump grey in ditches, storm sewers and in some desert states like Texas and New Mexico to name a few they actually encouraged folks to dump gray water around trees and shrubs at roadside rest and the like.

But along comes modern technology and research and suddenly we find out that some of the gray water contains enzymes and chemicals that can actually be more enviromentally harmful than black water.

I really think the industry just has not caught up with the idea yet of just one tank. And besides they would have to re-educate everyone so why bother. My opinion, put it all in one tank. DanT

**jcanavera** · 06-29-2003, 01:30 PM

One other nicety that a grey water tank gives. When you go to the dump station you dump black first then grey. The grey water dump flushes a lot of nastiness from the valve and hose.

Jack

RoadKingMoe · 06-29-2003, 01:58 PM

Quote:

Originally posted by DanT
I really think the industry just has not caught up with the idea yet of just one tank. And besides they would have to re-educate everyone so why bother. My opinion, put it all in one tank. DanT

That's what the folks at the Airstream factory told me they would be doing in all new trailers. One combined holding tank. Personally, I like having them separate.

pilgrim_still · 06-29-2003, 02:36 PM

Thanks, y'all, for your input.

My owner's manual says the tank is 17 gallons -- so, fill capacity would definitely be a limiting factor.

An auxiliary water tank (is this what you mean by a "blue" tank?) seems the standard solution.

...still, on the road to wash-up for lunch, is sure would be handy to divert the soapy water into the black tank.

Silvertwinkie · 06-29-2003, 02:54 PM

I like having a seperate grey and black tank. I think it would be a big mistake to make it only one big tank.

I hope that they reconsider.

Eric

Chas · 06-29-2003, 05:34 PM

I would rather have it all in one as long as it is a big tank. I always have had a tough time getting enough liquid into the black tank to get it to behave correctly. The exact problems I had due to insufficient liquid along with the solid waste is something I would rather not get into specifically, for both of our sakes.

I am sure there is a way to plumb it to keep the tank from backing up into the shower, putting the toilet lower than the shower is the first thing that comes to mind.

When it was all in one like on my truck camper I never had a problem, plenty of grey water to flush everything right out in one quick pull of the valve.

Chas

**jcanavera** · 06-29-2003, 08:45 PM

Quote:

Originally posted by RoadKingMoe

That's what the folks at the Airstream factory told me they would be doing in all new trailers. One combined holding tank. Personally, I like having them separate.

I agree. This would be a big mistake in my estimation. Those of you who would like to express their thoughts to Airstream, here is their suggestion email address. I plan on dropping them a line.

suggestions@airstream.com

Jack

Silvertwinkie · 06-30-2003, 06:05 AM

In my case, the grey fills far faster than the black tank. In a way, I can kind if see the point. Here I have a 24.5 gal fresh water tank and almost 2x that in wastewater storage....however, that only works if you are going off the pump. What if you are connected to water? I suppose in most cases if there is a water hookup, there is also a sewer hookup as well....but I still think seperate tanks is the best option. Like Jack, I pull the black tank first and then follow it with the grey tank to help purge the nasties from the hose.

Also, here is one other reason (for me) why the dual tanks are a better idea.

If you go camping and have no dump station (it does happen), I can safely dump the grey water (at most places I go) and loose that weight rather than haul it until I can get to a dump station (be it at a rest area or otherwise). To me withy my 21 gal tank, that is about 180lbs of less dead weight. Add that to the fresh water tank I purge when I'm on the road home (another 200+lbs) and you can see that with both tanks empty, I save at the very least 380lbs in weight. When you are counting lbs., that in my case is a substantial reduction in weight and hopefully will translate into some fuel economy.

Eric