Plumbing System in our DIY RV Camper Van

We spent quite a bit of time designing our Promaster camper van layout, and considerations for plumbing, including water and waste tanks were very important. Our floorplan ended up with a full size raised bed platform across the rear of the van. On the driver side, we designed the RV van to have a wet bath in front of the bed. On the passenger or sliding door side, our layout design included a galley kitchen cabinet with a sink and residential style faucet. We wanted to be able to camp in below freezing weather, so all of our plumbing and water and waste tanks are inside the camper van. We used the floor space under the rear bed to locate the fresh water tank, water heater, and gray water waste tank. From our research, trying to locate all water tanks under the van would be much more time consuming and difficult to have tanks with much quantity. Others have done this, so many design options are possible.

DIY RV Floor Plan Promaster DIY Promaster RV Van Floor Plan

We have other types of RVs, so dumping waste tanks is not a real issue for us. Our design allows us to go 4 to 5 days between needing to dump tanks and refill fresh water. This includes cooking, food and meal prep, all toilet needs, and showers at least every other day. We wanted the ability to shower after hiking or other outdoor activities, and our wet bath design lets us do this without the fuss of setup or tear down with a wet shower curtain.

So, now that we have described an overview, we can look at our plumbing and water system build in more detail. Once our design was finalized, we ordered our tanks so that we could dry fit all major items to determine the exact location. The picture below shows the black tank and shower pan located on the driver side, just in front of the right rear wheel. The gray tank is over the rear axle on the left side of the van. The height of the shower pan was very important in order to make sure that the shower drain was above the gray waste tank inlet. We used a low profile shower drain to accomplish this. Note that all of our major components and links to them are listed at the end of this post.

Tank locations for our DIY RV camper van wet bath
Tank locations for our DIY RV camper van wet bath

We located the 46 gallon fresh water tank on the right side of the van over the rear axle. We secured this tank with metal straps to prevent movement in the case of an accident. The 33 gallon gray waste tank was also over the rear axle but on the left side. These tanks are very close to the same height, and their size also left room in between for a IsoTemp marine style water heater that was heated by the van engine coolant. Also note in the picture below the wet bath shower wall on the left and the kitchen galley cabinet on the right. The tanks were placed flat on the van plywood floor to keep the center of gravity low, and there would still be room above them for folding bicycle and other storage under the rear bed.

Gray and fresh water tank locations under the bed of our camper van
Gray and fresh water tank locations under the bed of our camper van

The black tank drain was on the front or forward end of the van. We wanted one waste drain penetrating the van floor, so we routed the PVC drain from the gray tank along the floor, beside the black tank support frame, to the front of the black tank. We used a remote cable operated waste valve (1.5″) to control the gray water drain. The black tank also uses a remote operated RV waste valve (3″) right at the tank outlet. This connected to an elbow that turned down and went through the van floor. The elbow also had a side inlet so that we could connect the gray water drain into the same elbow. Under the van, we attached a short 3″ pipe and a standard bayonet adapter with a cap. Our two remote valve cables went through the van floor and the handles are located under the van, next to the 3 inch waste outlet.

Gray water and black tank drain configuration
Gray water and black tank drain configuration

The image below shows and overhead view of the drain valves. The white PVC on the left comes from the gray waste water tank and connects to the black ABS 3″ elbow. The white PVC connected to the black tank is the black tank vent. This routes upward, then through the wet bath wall, then continues its route upward in the corner of the wet bath and out through the van roof. This vent allows the black tank air to expand and contract with temperature and vent gasses outside of the van. It also allows air into the tank as it is drained.

Overhead view of gray tank drain pipe and black tank vent
Overhead view of gray tank drain pipe and black tank vent

The two items that drain into the gray waste water tank in our Promaster camp van are the shower and the galley (kitchen) sink. We did not have much vertical drop between our shower pan and the gray tank inlet, so we had to be creative. See our wet bath post for more details, but we use a low profile shower drain, some 1″ tubing, then a HepvO drain instead of a standard drain trap setup. The HepvO drain functions as a trap, but does not retain any water that might freeze during winter storage. In the photo below, the short blue PEX pipe and curved white PEX from the corner of the gray tank serve as the air vent for the gray waste tank. It is routed under the van and can also serve as an emergency overflow if the tank becomes too full.

Shower drain to the gray tank in our RV camper van
Shower drain to the gray tank in our RV camper van

On the passenger side of the van is the galley or kitchen cabinet. This contains a stainless steel undermount sink and a standard residential single handle faucet. The drain from this sink also uses a HepvO valve instead of a trap system. The only issue with plumbing items on both sides of the van is the need to get both drains to the gray tank. In our case, the drain from the galley sink crosses the middle of the van under the rear bed. We located it between two storage drawers to prevent it wasting much space. The photo below shows the drain line from the van sink over to the gray tank inlet.

Galley sink drain to gray tank in the camper van
Galley sink drain to gray tank in the camper van

The drain from the sink was easier to slope, since the vertical drop was significant to the gray waste water tank. The image below shows where the drain line and hot and cold water supply lines are located behind our microwave. PEX plumbing pipe is easy to cut and crimp onto fittings, and the tool to crimp the PEX rings is not too expensive.

Kitchen galley sink drain and supply lines in the DIY RV van
Kitchen galley sink drain and supply lines in the DIY RV van

On the fresh water supply side, our fresh water tank has a 1/2″ outlet at the bottom of the tank. This runs through a screen filter and then to the water pump. After the water pump, we installed an accumulator to regulate the water pressure and keep the pump from cycling frequently. This accumulator has a rubber bladder that allows water to partially fill it up until the pump shuts off. As water is used, the rubber bladder pushes out water and keeps the pressure higher for a longer period of time. The pump only needs to turn on when the pressure drops too low. We have a 3 way valve between the pump and accumulator to bypass the accumulator when using RV antifreeze to winterize the plumbing system before storage during a time of freezing temperatures.

Water pump and accumulator in our van plumbing system
Water pump and accumulator in our van plumbing system

After the accumulator, on the other side of the plywood cabinet end, is the water filter. We chose to use a residential style whole house water filter and a carbon filter cartridge. This is actually the same filter and cartridge that we use on our home water system, and we only have to keep one type of filter cartridge on hand for either system. The filter is inside the galley cabinet under the microwave. It is also bypassed by a 3 way valve so that RV antifreeze does not have to fill the filter housing when winterizing. We did have to make sure that the filter could be easily accessed to unscrew the cartridge holder and change out filter cartridges. In the image below, the filter cartridge and rest of the housing are not installed.

Residential water filter in our camper van plumbing system
Residential water filter in our camper van plumbing system

Our wet bath includes a standard RV toilet and uses a Nautilus retractable shower door by Stoett to avoid dealing with a wet shower curtain. In the photo below you can see the wet bath with a 24 x 32 shower pan and grab handle for easier entry and exit.

Camper van wet bath shower and toilet
Camper van wet bath shower and toilet

To fill the fresh water tank, we mounted our fill inlet inside the van in order to secure the fresh water and eliminate another hole cut through the side of the Promaster van metal skin. The lines to our shower faucet are also under the bed area. We are happy with the storage that is still available on top of the tanks and water heater.

Garage area under the bed with tanks and water heater
Garage area under the bed with tanks and water heater

We carry a 25 foot fresh water fill hose on the rear passenger door of the camper van. The door also holds our 30 amp electrical cord for the rare occasions that we connect to shore power. The picture below also shows another view of the fresh water fill inlet for our van plumbing system design.

Van rear door storage with fresh water fill hose and 30 amp cord
Van rear door storage with fresh water fill hose and 30 amp cord

Our entire plumbing design schematic is shown below detailing our camper van water system. Click the image to view a larger version.

Camper van RV plumbing and water system design
Camper van RV plumbing and water system design schematic

List of components used in the RV camper van plumbing system:

Fresh Water Supply Components

46 Gal TankClass A Customs 46 Gallon Fresh Water Tank – holds 4 to 5 days of use for us
Fresh InletWhite Fresh Water Fill Hatch RV Inlet – to fill fresh water tank
Fresh Fill Hose25ft Drinking Water Hose – Lead and BPA Free, Reinforced 5/8″Inner Diameter – to fill fresh water tank
Filter Strainer1/2″ Hose In-Line Strainer with Filter Screen – catches debris from fresh tank
3 way Valve3-Way by-Pass Crimp Valve (several needed)
Water PumpShurflo 4028 Water Pump – 2.3 GPM
AccumulatorShurflo 181-201 Accumulator Tank – smooths pressure surges from pump
Water FilterDuPont Universal Whole House Water Filtration System – holds filter catridges
Filter CartridgeCarbon Wrap Water Filter Cartridge
Kitchen FaucetDelta Faucet Essa Pull Down Kitchen Faucet – galley sink faucet
Shower FaucetTwo Handle RV Shower Faucet – for the shower wand
Shower WandOxygenics Fury Hand Held Shower Wand
Shower Wand Hose60-inch Stainless Steel Shower Hose – more flexible than plastic hoses

Water Heater Major Components

Water HeaterIsoTemp Spa 15 Marine Type Water Heater
BSP to NPTConverts output of mixing valve to standard 1/2″ NPT male for attached a pex swivel adapter.
Backflow PreventerPrevents hot water from leaking into cold water plumbing system
3/4 x 5/8 x 3/4 Tee3/4″ in and out, with a 5/8″ tee off at 90 degress, installed in short hoses from firewall, turned to point down toward the drive side of the engine bay, need 2
5/8 Barb Ball Valve5/8″ full flow ball valves installed right after the tees, allow the hoses under the Promaster RV van and water heater to be disconnected if needed, need 2
5/8 Barb to 1/2 NPT1/2″ NPT female to 5/8″ hose barb to connect heater hoses to water heater, 2 needed
5/8 Inch Heater HoseHeater hose for runs between water heater and engine bay, this is a 50 foot roll, and I need about 40 feet
Mopar CoolantOne gallon of additional coolant to fill the new heater hoses and water heater heat exchanger, I used just over 3/4 of the gallon

We also have a separate post detailing our RV camper van water heating solution.

Gray Water Drain System Components

33 Gallon TankClass A Customs 33 Gallon RV Water Tank
1.5″ Drain Valve1 1/2 Inch Remote Cable Operated RV Waste Valve
HepvO Drain ValveHepvO Sanitary Waste Valve, replaces standard drain P trap
Shower DrainScandvik Low Profile Shower Drain

Wet Bath & Toilet Components

18.5 Gal Black TankClass A Customs 18 1/2 Gallon Black Waste Holding Tank
24 x 32 Shower PanLippert 24″ x 32″ RV White Shower Pan
Retractable Shower DoorNautilus Retractable RV Shower Door (custom sizes available)
RV ToiletAqua-Magic V RV Toilet – Thetford 31667
3″ Drain Valve3 Inch Remote Cable Operated RV Waste Valve
Roof VentRV Roof Vent Cap, for black tank exterior venting
Sewer CapCamco Odor Free RV Sewer Cap 
Sewer HoseRV Sewer Hose Kit

Miscellaneous Items

Tank Level MeterGarnet SeeLevel II Tank Level Monitoring System 709, to see tank fluid levels with percentage measurements, much better than the old 1/3, 2/3, full meters
Galley SinkUndermount Single Bowl 16 by 18 Bar Sink, Stainless Steel
1/2″ Ball ValvePEX fittings, used in several locations to be able to shut off water to individual faucets in case of repairs or leaks

I hope that the information on our DIY RV Promaster camper van water and drain system was helpful. It has been working very well for us in over 50 days of camping as of this blog post.

We also created a YouTube video covering our class B camper van plumbing, water, and waste systems. Click the image below to view it.

Happy Trails…

4 thoughts on “Plumbing System in our DIY RV Camper Van”

  1. Shawn and Jana,

    Greatly appreciate your Isotemp installation post I found on PM Forum and additional heat exchanger and plumbing details at your blog. Like your philosophy for the build, and thoroughness and clarity of pictures and word descriptions. Answered many questions and raised others I will need to pursue for my particular design. Thank you for sharing.

    George and Lela Herzog, Beavercreek OH

    • No, you have to sit down in the shower. it might be possible for a shorter person to stand up if you were able to move the black tank under the van.

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