Cargo trailer bathroom plan

[TNGW1500SE]

Here's my plan (so far): I have a 12 foot cargo trailer to haul two motorcycles. The bikes take the back 8'. I pull it behind my Transit van. The van is done other than a NO BATHROOM. I'm building a bathroom in front of trailer. I'm doing water tanks now. I bought two 20 gallon tanks. One for grey and on for fresh on top of each other. Those 2 are mounted on the wall opposite the door (North to South). Custom shower is in the "V". Small sink next to shower in "V" passenger side. Shower and sink drain into a plastic box (for a boat shower) under the floor with a float switch and a 12 volt pump in it. It pumps the shower and sink into the grey tank with a check valve in the hose. I tested it and it works great BUT......... I'm changing plan a little. I was going to use a toilet with those bags. Almost just a bucket with a snap on seat. I don't want to deal with that. I want a RV toilet and black tank.

New plan: I looked a black tanks and was thinking small (8 gallons) but I don't want to have to dump every other day,,, so..... Buy 27 gallon tank. Then raise my "stacked" grey and fresh maybe 5 inches off the floor. Cut the floor out 17 x 36 (East to West) to allow a black tank to be mounted "partly" under the trailer and protrude up into the bathroom about 3 1/2 inches above the floor. The black tank is 36x17x10. Eighteen & 1/2 inches (with of the length (36) will be under the other tanks in an "L" shape. The other end of the black tank (shallow side) sticks up above the floor toward the door. I'll build around it with 2x4's on edge. Cover those with plywood and mount a low profile toilet on top. That gets the black tank up off the road and the drain comes out just below the bottom edge of the trailer in front of the axle.

The low profile toilet gains me 4 1/2 inches for the toilet platform and I still maintain correct seat height.

MOTE: On my old motorhome, I'd use grey water to flush the back tank. It had three valves plumbed in a "T".

I'm thinking about plumbing this so that the grey water could drain into the black tank vent (using a gate valve) to flush it after the black was emptied. The grey is my highest tank so gravity would do the work. I'd also have the option of just draining the grey separately through a garden hose.

Question #1: Anything wrong with that plan? The floor plan works for us.

Question #2: Wife asked why not flush the toilet with grey water and not waste fresh just to flush. Does anyone do that? Seems like the grey would stink.

ANY AND ALL ADVICE ACCEPTED 😉

[ktmrfs]

I have a 14' cargo/bike trailer with full living quarters that we've used for almost 20 years. for a 5 day or so outing with 2 people, we have a 40 gallon grey and a 15 gallon fresh. Extra fresh water in 7 gallon blue jugs if needed, And a porta potti with a 5 gallon tank. has gas water heater and shower. We have NEVER filled the porta potti and NEVER come anywhere near filling the grey even with showers, sink, etc.

I looked at a toilet and black tank, just wasn't worth the effort for us.

[valhalla360]

TNGW1500SE wrote:

1995brave wrote:
How about a cassette toilet? Then you have a small black tank built into the toilet that you take out and dump.

I looked at those, Also looked at a composting one. I'd rather have that but they're 1000 bucks for a good one.

Since you are into building, look online. It's not hard to build a composting toilet for a lot less than $1000.

While I normally wouldn't recommend on for an RV, with your use case, they would make a lot of sense and solve so many of the issues you are presented with.

Look online and you can find lots of examples.

We had a Natures Head on our boat but I would go with the C-head or build a knock off of it as I like the 5gal bucket approach for the solids container.

[Tiger4x4RV]

Thetford Porta-Potti. I used one for 15 years, 1991-2006. They cost about $100 back then, undoubtedly more now. The PP sat in the shower stall, was easily removed to improve showering. Black tank was about 5 gallons. It flushed from its own small fresh water tank. No bad smells. You could get a second black tank and swap out tanks to extend your time between dumps.

It is totally a myth that you can dump these or dump built-in cassettes anywhere you want. Find a safe and legal dump station.

[Cummins12V98]

I can save you a lot of money. 5 gallon bucket with a pc of pipe insulation on the top edge for comfort. Same thing on my Boat.

[TNGW1500SE]

1995brave wrote:
How about a cassette toilet? Then you have a small black tank built into the toilet that you take out and dump.

I looked at those, Also looked at a composting one. I'd rather have that but they're 1000 bucks for a good one.

[1995brave]

How about a cassette toilet? Then you have a small black tank built into the toilet that you take out and dump.