I just bought a new TT (Open Range 216RBS) and it has 2 gray water tanks. Both are 31 gallons. One is connected to the kitchen sink and one is connected to the shower and bath sink. They have separate dump valves and fittings. The kitchen sink tank drain is on the front driver side of the TT and the bath drain is in the normal place.I can't imagine why a manufacturer would think this is a good set up. We will normally put about 5-10 gallons in the kitchen tank and of course, the bath tank fills pretty quick. So here I am with a full bath tank and 25 gallon of unusable empty tank capacity in the other tank.I want to connect the two tanks together so they function as a single tank. Of course the TT has a fully enclosed underbelly attached with large rivets instead of screws just to make access difficult.Anybody ever connected two gray tanks to function as a single large tank? Are there some other secret tricks to gray water management with two tanks?

Didn't you buy it knowing it had two tanks?

Didn't you buy it knowing it had two tanks?Now that's helpful...

I see no problem. Thetford and others make a "Y" exactly for that purpose. Heck, even high end fivers do this, especially rear kitchen models.

We too have two gray tanks but it actually works for us. We fill both about the same, but think that's the case for us because we are conservative for both. We take "Navy" showers, collecting the water in a bucket from the showerhead before it warms up and use that collected water in the toilet. For the kitchen sink, we use one dish pan of soapy water a day; wiping plates clean before washing or using paper plates. We use biodegradable dish soap so if the tank gets close to full, we will empty that water into a separate bucket and use it to put our campfire out. I've heard of people connecting the two but for us it's not a big issue.

Two Gray Tanks | Good Sam Community

25 Replies

Sprink-Fitter
Explorer
Aug 04, 2015
Dog Trainer wrote:
Sprink-Fitter wrote:
Didn't you buy it knowing it had two tanks?

This is the kind of post and response that is making this forum less and less valuable over the years. No purpose or content that can help the OP just a smart comment that reeks of holier than thou. Thanks you added a lot.

To me he sounded surprised it had two tanks. Sorry I asked a question.
SprinklerMan
Explorer
Aug 03, 2015
Old-Biscuit wrote:
Why 2 separate tanks with separate drains........

Probably due to tank locations and not being able to have enough drain slope to connect aft tank to forward tank--------other items in way of routing piping, frame in the way etc. etc.

Just remember IF you change drain line piping.......it has to have enough slope so that debris/particles do not build up.

Its grey water , you could get a reducer tee and make the equalizer pipe 1.5 inch . You will have no wiggle room to connect the two together . You will need a rubber fernco
Dog_Trainer
Explorer
Aug 03, 2015
Sprink-Fitter wrote:
Didn't you buy it knowing it had two tanks?

This is the kind of post and response that is making this forum less and less valuable over the years. No purpose or content that can help the OP just a smart comment that reeks of holier than thou. Thanks you added a lot.
hohenwald48
Explorer
Aug 03, 2015
TUCQUALA wrote:
Never planned on going inside the underbelly. That would have been a whole lot of extra work, which I have an aversion to!!! Also, the slide racks would have been in the way probably. Mod took about 1.5 hrs, 3 cuts on the orig pipes, and a small amount of ABS cement. No rivets were harmed during filming of this event!!!!!

Yes, the valves are inside, and as you can see the tanks feed outside the belly after a good drop. Inside probably would have had poorer drain slope.

As to the debris issue, or standing water, I do have a hose cap on the 3" cap that can be used to drain any remaining water when in driveway, and trailer is in a very down nose attitude till finished leveling. I generally do all flushing at home, and down the toilet. Less time in the dump stations!!!

Heading to Lowes to get parts. I plan to do it exactly the same way you did with only small changes. I think I'm going to use flexible pool pump hose instead of hard pipe and I'm going to install additional blade valves on both outlet pipes so I don't have to deal with water behind the screw on caps. I too have no desire to harm any rivets. I'll post the results when I'm finished.
Ray552
Explorer
Aug 03, 2015
I have two gray tanks and am now thinking about putting dye in one filling it up and seeing if I get dye out of the other valve.

I have often thought where did I get so much water when dumping that back tank. I have an out door kitchen that I know drains to it but I often have a lot of water in it that I have no idea where it could have come from as I do not use that sink very often and then never run a lot of water. I suspect they are connected.

I have never had the grey or black water be a problem even after camping 7 days without a hookup that was with 3 people.
TUCQUALA
Explorer
Aug 02, 2015
Never planned on going inside the underbelly. That would have been a whole lot of extra work, which I have an aversion to!!! Also, the slide racks would have been in the way probably. Mod took about 1.5 hrs, 3 cuts on the orig pipes, and a small amount of ABS cement. No rivets were harmed during filming of this event!!!!!

Yes, the valves are inside, and as you can see the tanks feed outside the belly after a good drop. Inside probably would have had poorer drain slope.

As to the debris issue, or standing water, I do have a hose cap on the 3" cap that can be used to drain any remaining water when in driveway, and trailer is in a very down nose attitude till finished leveling. I generally do all flushing at home, and down the toilet. Less time in the dump stations!!!
Peg_Leg
Explorer
Aug 02, 2015
I was going to try this on my old 31' Dutchmen TT. It had a dump in front of the axles for the kitchen and another behind the axles for the black and shower. I just mainly wanted to eliminate the need of making connections twice when dumping. Upon removal of the under covering I couldn't find a path to route the plumbing that would allow full drainage.

I don't envy you drilling out all those rivets. I can imagine a couple being hard to access with a drill. I just know that the RV industry has make vast improvements in this century and your adaptation will be a snap. Just look at how you have rivets instead of screws and all the accurate information the salesman gave you.

Good luck but RV or not, plumbing still sucks.
hohenwald48
Explorer
Aug 02, 2015
TUCQUALA,
Thanks for the great pix. That's exactly what I was thinking of doing. I noticed you ran the new plumbing outside the underbelly, I assume you are not worried about freezing. Did you think about running the new pipes inside the underbelly or is it just not necessary for your application?

(EDIT) Oops. I just noticed all your new pipes are downstream of the slide valves so I suppose they are normally dry pipes.

I can't imagine particle accumulation being any kind of issue in the gray lines.
TUCQUALA
Explorer
Aug 02, 2015
I recently finished connecting the rear kitchen tank to the 3" outlet forward of the wheels on our Timber Ridge. For me it was so I don't have to have 2 hoses out or a garden hose. Now, I drain the black, drain the kitchen tank, and drain the bath tank. I can leave both grays open if in a hookup spot. Works like it should have in the first place. No problem as far as slope, I don't believe that there will be a problem with debris as the rear tank empties completely.

Where the new 1-1/2" pipe crosses the cutouts for slide motor access, I installed rubber couplers and clamps for unintended removal!!!
Old-Biscuit
Explorer III
Aug 02, 2015
Why 2 separate tanks with separate drains........

Probably due to tank locations and not being able to have enough drain slope to connect aft tank to forward tank--------other items in way of routing piping, frame in the way etc. etc.

Just remember IF you change drain line piping.......it has to have enough slope so that debris/particles do not build up.