Gray tank in belly

[nickknack]

Hi all, I'm converting our '77 Argosy from rear bath to mid-bath. In order to do so, I'll need to put the gray tank bewteen the axels. This should be a plus for weight distribution and get rid of the typical rear-end separation.

However, I'm running into a problem with plumbing the actual tank. I have about 5" to work with under the subfloor, but I also know I need to have the shower/sinks flow into the tank from the top, which means I probably need something like 2-3" for that plumbing.

What is the best solution here, has anyone done their gray tank fully under the sub-floor? And if so, what was your solution for this issue?

I've already got the shell off and frame structure ready for rust prevention, so any type of solution is in the cards at this point.

Thanks!

[Bubba L]

I don’t think you have to drain into the top of the tank. If your shower drain is at the top of your subfloor, you can place a short 90, place a Hepvo trap and drain into the side of the tank. The water will fill the tank up to the level of the drain. The Hepvo will disallow water to back into the shower. I have two 16 gallon tanks that are connected low on the sides. Both tanks will fill with the shower connected to the side. Water seeks its own level, so both tanks have equal levels. I got the idea from Colin Hyde. I may have pictures on our renovation thread. I’m sure someone else can explain it more clearly. By the way, our chassis frame is only 4”. Good luck

[SSquared]

On my 2013 25FB, the floor of the shower is a few inches higher than the main floor. The drain goes into a P trap, then has a near-horizontal run aft for a couple of feet, then an elbow, then another near-horizontal run to a T which dumps into the top of the gray tank. So that's another way to do it.



BTW, the T has an air admittance valve on top (which gets dirty water splashed up into it if I tow with a full gray tank).

[Mx468]

I just installed a 25 gallon grey tank in my 72 safari a few months back, I basically plumbed the shower drain to the grey tank but at its highest point from the side that I could put it. I also have a hepvo valve which I haven't installed to my shower drain yet. That should help with any back flow.

[57Vintage]

I agree with Bubba, you can put your fittings on the side. On my 2 GW tanks I have fittings on both top and side. They're both below the sub-floor.

Also keep in mind that if headroom allows, you could raise your shower tray a little. Considering how much shorter these drain lines are vs. a house, a fraction of an inch can offer a solution. I had to raise my tub 3/4" to get enough slope on the drain line.

Just a note about my experience with the Hepvo traps. I found that water could leak back into the bath tub. I think it was a unique combination of a full GW tank and traveling over mountain grades. The drain goes into the rear corner of the GW tank and all that water created enough pressure for a little leakage. It's only happened once, but to make sure I added a Valterra valve to the drain line that I close when we're on the road. No big deal.

[Bubba L]

Originally Posted by 57Vintage

I agree with Bubba, you can put your fittings on the side. On my 2 GW tanks I have fittings on both top and side. They're both below the sub-floor.

Also keep in mind that if headroom allows, you could raise your shower tray a little. Considering how much shorter these drain lines are vs. a house, a fraction of an inch can offer a solution. I had to raise my tub 3/4" to get enough slope on the drain line.

Just a note about my experience with the Hepvo traps. I found that water could leak back into the bath tub. I think it was a unique combination of a full GW tank and traveling over mountain grades. The drain goes into the rear corner of the GW tank and all that water created enough pressure for a little leakage. It's only happened once, but to make sure I added a Valterra valve to the drain line that I close when we're on the road. No big deal.

Now you have me thinking Harold. I haven’t really used the shower, but maybe I’ll add a ball valve underneath just in case. I have the shower piping to the gray tank covered with a piece of the belly pan installed with rivnuts in the event I need to replace the Hepvo. Thanks for the heads up.

[57Vintage]

Originally Posted by Bubba L

Now you have me thinking Harold. I haven’t really used the shower, but maybe I’ll add a ball valve underneath just in case. I have the shower piping to the gray tank covered with a piece of the belly pan installed with rivnuts in the event I need to replace the Hepvo. Thanks for the heads up.

Hope you can install somewhere easily accessible. Mine's under the curb side twin bed.

[nickknack]

Lots of great information here... thank you all! Seems like HepVO is the way to go. One last question is where would I locate the dump valve for a mid-bath? Is there any reason it needs to be super close to the tank? Or can I run the pipe to the back of the trailer where the previous one came through the bumper? If it helps, I’m using a composting toilet, so no black tank.

[57Vintage]

As long as you get sufficient slope go wherever you want. Without a tank in the rear I'd tend to want the drain closer to the tank. Less chance of damage in case you accidently drag the bumper on the ground. Probably not real close to wheels in case they throw up road debris.

If you don't have a sewer hose yet, or plan to replace, I'd suggest looking at Lippert's system. They don't use ears to secure the hose it's a cam lock fitting.

http://drainmaster.com/rv/products/full-view/100187

[Mx468]

If you put the dump valve in back you'll have extra grey water space within the pipes to use.

[Mx468]

Originally Posted by nickknack

Lots of great information here... thank you all! Seems like HepVO is the way to go. One last question is where would I locate the dump valve for a mid-bath? Is there any reason it needs to be super close to the tank? Or can I run the pipe to the back of the trailer where the previous one came through the bumper? If it helps, I’m using a composting toilet, so no black tank.

Hey nicknack I also have a composting toilet, a Natures Head which I diverted the urine into my grey tank. Just a thought....

[nickknack]

Originally Posted by Mx468

If you put the dump valve in back you'll have extra grey water space within the pipes to use.

My thoughts exactly!

[nickknack]

Originally Posted by Mx468

Hey nicknack I also have a composting toilet, a Natures Head which I diverted the urine into my grey tank. Just a thought....

I was planning on doing the same... great minds and all!

[Mx468]

If you need any help pm me and you can pick my brain on how I set everything up while it’s still fresh up in the ole noggin but you better hurry it’s fading fast

[Blues Bill]

By chance do you have more pictures of your tank installation? I'm wanting to put GW tanks in my 1971 25' Tradewind.

[DougE]

The vent location will determine the fill level of the tank. If you have a vent at the top of the tank it can fill completely.