Wet Bath Installation in a DIY RV Camper Van

Wet Bath Design and Install in our Promaster RV Van:

When designing our camper van, we were very much in favor of a permanent shower and toilet setup. Having owned several RVs previously, the issue of black and gray tanks were not unknown, and they can be dealt with fairly easily. We had used a wet bath in a popup trailer some years ago, but there were no walls, and the shower curtain had to be put up and taken down and allowed to dry. We were interested in a more efficient solution.

Many camper van owners choose different toilet options. Some opt for a composting toilet, which seems to allow for a longer time between dumping solids, but the urine tank must be emptied nearly every day with regular use. Many who own a composting toilet in an RV talk of using a black trash bag to dump solids into, and then they deposit this in a trash dumpster. This does not seem to us to be a truly environmentally friendly or composting solution. Others decide that a cassette toilet works for them. This is a toilet with its own ‘black tank’ to hold all waste. This would need to be dumped every day or two with normal use based on our estimate. We were not too excited about having to haul a 40+ pound tank of waste into a restroom and then dump it into a toilet.

For us, we decided that an RV toilet with a separate blank tank would be our best option. The black tank can be easily dumped along with our gray water tank, it does not require hauling a waste tank by hand into a restroom, and it could be integrated into a wet bath design as well as the other options.

DIY RV Floor Plan Promaster
WanderingWakes.net DIY Promaster RV Van Floor Plan

In our floorplan, the wet bath would be just in front of the right rear wheel on the driver side. This seemed to offer the most open plan and did not feel too closed in. It is important to determine where the drain will exit the van floor. In our case, the 3″ drain would be in front of the black tank, under our wardrobe, and would be opened with a remote waste valve.

Once we decided on the wet bath location, we determined that an 18.5 gallon black tank from Class A Customs would work very well. This tank would fit under a 24″ x 32″ shower pan, so that the toilet and wet bath compartment would be directly above the black tank. We would lose some head room, but sitting on the toilet to shower works just fine.

First, we used painter’s tape to make our general floor plan on the van plywood floor. Then we fit the blank tank in place and made sure that the drain would miss any framing under the metal floor. We wanted our black tank inside the van for a couple of reasons. First, having it in the van would prevent any freezing when camping in cold weather. Also, having the black tank above the floor would allow a larger ‘drop’ when draining the tank and make it easier to empty. The tank would also not be below the van where road debris or curbs or large rocks might damage it when driving lesser roads.

Dry fitting the black tank on our DIY RV camper van wet bath
Dry fitting the black tank on our DIY RV camper van wet bath

Next, we test fit the shower pan over the black tank. This was important to make sure that our drain would work for the shower. It was also necessary to make sure that the toilet flange for the toilet would enter the black tank where a 3″ rubber grommet could be installed. The RV toilet would empty through the shower pan and into the deepest (drain) end of the black tank.

Dry fitting the shower pan over the black tank in our DIY RV camper van
Dry fitting the shower pan over the black tank in our DIY RV camper van
Tank locations for our DIY RV camper van wet bath
Tank locations for our DIY RV camper van wet bath

Now that our location was determined after careful planning and measuring, we mounted the plywood support frame and black tank in the van. In the picture below, you can see the location of the 3″ grommet for the toilet connection, and the 1.5″ grommet for the tank vent. These grommets are installed after cutting the proper size hole with a hole saw – our 3″ grommet need a 4″ hole saw and our 1.5″ grommet needed a 2.5″ hole saw. The vent will be routed through the van roof and allows vapors to exit the tank and prevents any pressure build up due to temperature changes or other factors. We also used metal straps to secure the tank to the van structure. It was bolted through metal framing on the side and through the metal floor on the bottom.

Installing the black tank in our DIY RV camper van wet bath
Installing the black tank in our DIY RV camper van wet bath

Once the black tank was secured, we built a plywood frame to support the Lippert 24″ x 32″ shower pan. The black tank is not designed to support weight on top of it, so the plywood shower pan support distributes the weight to plywood legs to support the shower pan and plywood shower walls that will be installed. We had to be very careful to align the hole we drilled in the shower pan with the hole in the black tank. We then installed the toilet flange and pipe into the black tank 3″ grommet. A metal band clamp is installed around the grommet to compress it against the PVC pipe from the toilet flange. The flange was mounted with white Sikaflex 221 and deck screws through the shower pan and into 3/4″ plywood under the pan.

Toilet flange install in our DIY RV camper van shower
Toilet flange install in our DIY RV camper van shower

The drain for the shower is difficult to see, but we used a Scandvik 10307 Low Profile Elbow Shower/Cockpit Drain with a 1″ outlet. We did not have much vertical drop to work with before the drain entered the end of the gray tank. We used the Scandvik drain, then 1″ clear tubing, a 90 degree barbed elbow, then more 1″ clear tubing to a HepvO valve. The HepvO valve replaces a standard drain P trap, and it will not hold water that might freeze. We used one on the shower and one on our galley sink.

Wet bath shower drain in our DIY RV camper van
Wet bath shower drain in our DIY RV camper van

Once the wet bath shower pan was in place and mounted, we used cardboard pieces to determine the exact shape of the plywood walls. We used 1/2″ baltic birch plywood for the end walls of our wet bath shower.

Cardboard aided design for our wet bath shower walls
Cardboard aided design for our wet bath shower walls

Once the 1/2″ plywood walls were cut t the correct shape, we installed them with pocket screws where need to mount them to our shower plywood base. We also use wood strips mounted to the van framing on the ceiling and back wall to tie it all together. The picture below shows the end walls installed and the back framing before adding Havelock wool insulation on the back wall area.

Wet bath shower walls installed for our DIY RV camper van
Wet bath shower walls installed for our DIY RV camper van

On the back walls and ceiling, we used 1/4″ plywood to allow the material to follow the curve of the van side wall and the roof. We primed and caulked all of the interior walls and seams before gluing in the plastic shower liner material. In the photo below, the small hole in the lower right corner is for the black tank vent. We opted to route the black tank vent pipe through the corner of the wet bath shower in order to free up space in our wardrobe area.

Wet bath shower walls ready for plastic lining in our wet bath
Wet bath shower walls ready for plastic lining in our RV van

The image below shows the route of the black tank vent pipe from the tank front and up into the corner of the wet bath. You can also see the blue PEX pipe and ball valve shutoff that will supply the water to our toilet.

Black tank vent detail for our RV van wet bath shower
Black tank vent detail for our RV van wet bath shower
Black tank vent cap on the DIY RV camper van roof
Black tank vent cap on the DIY RV camper van roof

Once the walls were ready, we glued plastic panels to the interior walls of the shower and caulked all corners with 100% white silicone caulk. We initially glued in Plas-Tex waterproof wall panels by Parkland Performance that were 0.060″ thick. DO NOT USE these panels. They expand and contract and pull loose from the corners and buckle up away from the glue. We removed those with some difficulty and cut to size and installed 4 ft. x 8 ft. White .090 FRP Wall Board by Glasliner. These have a glossy surface that is slightly textured. They have held up very well and not moved at all after multiple trips and many months of hot and cold.

Clamping the white panels to the wet bath shower walls.
Clamping the white panels to the wet bath shower walls.

Unfortunately, the picture below is out of focus, but you can see the route of the vent pipe in the corner of the wet bath, as well as the faucet and grab handle locations. The faucet location is low so that it is underneath our raised bed. The handle makes it easier to step in and out of the bath since it is a raised shower pan.

Vent and faucet installed in the wet bath shower
Vent and faucet installed in the wet bath shower

Below, you can see that the toilet has been mounted, along with the shower hand wand. We decided that we did not want or need a shower head mounted up high on the wall. In other RVs, the shower head / wand has fallen off during travel. We have a stainless steel hook and elastic strap to hold the wand securely out of the way until showering. We replaced the stiff plastic shower wand hose with a flexible stainless steel version, and slip-on toilet paper holder makes it easy to remove the paper when it it time to shower. We still need to install the LED ceiling light and shower door, but we are getting close on this project.

Wet bath before installing the Nautilus retractable shower door
Wet bath before installing the Nautilus retractable shower door

We are very happy with our Nautilus retractable shower door by Stoett Industries. This door retracts out of the way when not need and is so much easier and more water tight than a shower curtain. It has a wiper to squeegee off the water as it is rolled up. They were very helpful and cut the door to the exact height that we needed.

Nautilus wet bath shower door by Stoett Industries
Nautilus wet bath shower door by Stoett Industries

Below is the finished look of our wet bath shower. We added a mesh net for small bottles and soap. The wet bath allows us to be fully self contained and not need to seek out other options for bathroom or shower needs. We also carry a synthetic chamois drying towel to wipe down the walls after showering. This prevents excess moisture from staying in the van. We also usually run the roof vent with a window slightly open to vent extra moisture. Our holding tanks allow 4 to 5 days of full time use before we have to dump. Dumping gray and black tanks at a park or campground dump station is quick and simple. Our waste valves with the remote cable and handles under the van make it easy for one person to take care of the task.

Finished look of our DIY RV camper van wet bath shower
Finished look of our DIY RV camper van wet bath shower

Products and tools used in this project:

Black TankClass A Customs 18.5 Gallon RV Waste Black Water Holding Tank WT-1850
Tie Down StrapsSimpson Strong Tie LSTA36 18-Gauge 1-1/4-Inch by 36-Inch Strap
3″ Grommet3 inch Rubber Grommet for an RV Waste Tank (for toilet flange)
4″ Clamp4 inch Stainless Steel Adjustable Hose Clamp (for 3″ grommet)
4″ Hole Saw4 inch Heave Duty Hole Saw (for 3″ grommet)
1.5″ Grommet1 1/2 inch Rubber Grommet Holding Tank Fitting (for vent)
2.5″ Clamp2 1/2 inch Stainless Steel Adjustable Hose Clamp (for 1.5″ grommet)
2.5″ Hole Saw2 1/2 inch Heave Duty Hole Saw (for 1.5″ grommet)
3″ Valve3″ x 48″ Cable Waste Valve (to drain black tank)
Shower PanLippert 210369 White 24″ x 32″ Rectangular Left Handed Shower Pan
Toilet Flange4″ PVC Toilet Closet Flange
White SealantSikaflex 221 White Sealant Caulk (for toilet flange)
Shower DrainScandvik 10307 Low Profile Elbow Shower/Cockpit Drain, 1″ Outlet
Drain TrapWavin BV1B/UB HepvO Sanitary Waste Valve – 1-1/2″ (for shower drain to gray tank)
Gray TankClass A Customs RV Fresh / Gray Water 33 Gallon Tank T-3300
Shower FaucetValterra PF213350 Shower Two Handle Faucet Valve
Shower HoseDura Faucet DF-SA200-CP RV 60-inch Stainless Steel Shower Hose (Chrome)
Shower HeadOxygenics 92189 Fury Hand Held Shower Wand Sprayer Chrome
Grab HandleWhite Plastic RV Grab Handle
Toilet Paper HolderiDesign Plastic Wall Mount Toilet Paper Holder
LED Light5 inch Dimmable RV White Ceiling LED Light
Roof VentRV Roof Plumbing Tank Vent, Black
White Caulk100% Silicone White Caulk Sealant
Shower DoorNautilus 55″x36″ RV Shower Door Opaque Stripe, White
Drying ClothThe Absorber Synthetic Drying Chamois, 27″ x 17″

We have now used this wet bath and shower setup for 8 months and over 50 days and nights of camping and travelling. The toilet is very nice to have easily available at any time. To shower, we simply remove the toilet paper and small carpet square from the floor, close the door, and shower sitting down. I have not seen any issues or found anything that I might do different in a future van build. Whatever your toilet or shower choice, we wish you well and hope you are as satisfied as we are.

We have produced a YouTube video detailing the Promaster RV wet bath shower and toilet install that provides more detail. Click the image below to view our wet bath toilet and shower build tour.

Happy Trails…

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