REI version: https://www.rei.com/blog/camp/diy-car-top-solar-camp-shower

Yakima version: https://explore.yakima.com/roadshower (cost $330 up to $550)

Word version of these instructions: CarTopWasher.docx

* Note: Available means this much water might be delivered under pressure.

• The end cap gets a Schrader valve, shut-off valve and relief valve. (Update: I have never used the dang Schrader valve – why did I bother?) This stuff is all a tight fit on a four-inch end cap. They are also hard to make a solid pressure tight seal. Remember to install such that backing nuts, washers, etc that are inside the end cap allow clearance for you to install the end cap onto the pipe correctly.
• Option A (my version): Drill the holes undersize and then cut threads into the plastic ABS. I could not find proper tapping die, so I used a shop trick: took some scrap pipe fittings and cut slots in the threads so I could use these to tap threads into the plastic. This is tricky. I didn’t get the threads straight on the first try and when I pressure tested the final assembly it leaked. (Had to cut the thing off and have a little re-do.)
• Option B: use “Bulkhead Fittings”, sometimes called Tank Fittings. These make a really dependable seal through vessel wall material. It’s a more sure thing, but this will cause the fittings to extend a little further out from the end of the pipe. I could not find any in town. There are plenty on-line. You might have trouble getting these to all fit in the one end-cap. They normally take a bit more room for gaskets and interior thread. One other advantage to these is that if there’s a problem with a fitting, it’s an easy re-fit. If you did Option A, you get to cut the end cap off and rebuild from scratch.

• ABS straight pipe, 4-in, schedule 40: typical in 10-ft lengths. I cut a 6 ft length and two one-foot lengths. I ended up with about 7-ft total pipe volume.
• ABS 4-in fittings:
  • One 45-degree elbow (to make elevated one-foot end for air reservoir).
  • One “Clean out” Tee fitting (two straight ends smooth bore, the other threaded for a plug).
  • One Clean out threaded plug fitting.
  • Two 4-in end caps. Make sure these are flat surface model so you can drill, thread and mount fittings. Some that I looked at had trademark or other features molded in that would have messed up the install.
• One Schrader valve, plus One brass lock-nut. Hardware Sales has two versions of Schrader. One with ½-in thread, the other with 3/8-in thread. I did the 1/2-in version because it’s buggerly to cut threads into the ABS. I bought a spare one and used various cutting tools to make it into a tapping die. UPDATE (6/23/2020), I have never used the Schrader valve … I would not install one next time.
• One quarter-turn ball valve, ½-in pipe thread mounting. (Hardware Sales). A normal garden spigot would work, but you won’t want to poop around with multiple turns while using this system.
• One Pressure Relief Valve, ¾-in pipe thread, 100 psi set release with manual toggle. Search any hardware store. If you can find ½-in pipe thread it might be better.
• One ½-inch female thread 90, to hose barb connect. Prefer plastic. This device installs on inside of ball-valve such that the opening is pointed down near the bottom of the installed pipe. The idea is to pull water off the bottom of the reservoir.
• One ¾-in female thread 90 to hose barb connect. Prefer Plastic. Installs on inside thread of the relief valve so that it relieves air from top of installed pipe.
• One 25-ft length garden hose.
• One hose spray nozzle with shut-off valve. Reference Lowe’s: Item # 204693 Model # 8815 Yardsmith 1-Pattern Nozzle. This is important to have quick shut off in your hand because the system doesn’t have extra water.
• One garden hose “Gender Bender” fitting adapter for connecting male hose end to male hose fitting. (This is for filling the system from your house.)
• Two stainless screw type clamps. These are just hose-clamp looking things except they need to be a foot or two long. I used these to clamp the pipe to the car rack members, then I covered them with electricians’ tape.
• Foam pad for mounting the pipe. Ideally the pipe should slope toward the outlet valve.

Below are my home-made tapping die. Not shown here are the curse words and multiple hurled objects of frustration. I would be happy to loan these to anyone else interested in doing this build. Except these units have been cast into the deepest part of the inner circle of hell. Almost any plumber or electrician will have proper pipe thread cutting die laying around. Oh yeah. Don’t drill the hole to the pipe O.D. You have to drill smaller one size to leave thread material in the hole. Just in case you thought this was easy.