In this tutorial I will explain how I made a grey and black water tank out of two 55gal. drums. I took two 55gal barrels and cut them in half vertically, butted the two pieces together top to top and welded 16 gauge sheet metal to the top. I have one for black water, which the top picture is and one for grey water which is pictured below.
I priced 35 gal plastic holding tanks online and found they were around $200 – $250 each plus shipping. I have about $75 invested in both tanks between the two 16 gauge steel sheets I had to buy and the welding wire.
I got the barrels for free from a local boat manufacturing company. They originally held rubber cement which made them very easy to clean out as I just pulled the remaining dried cement out. The barrels had removable lids so i didn't have to cut the tops off. I measured the circumference of the barrels and marked two lines at the top and bottom half the distance of the circumference. I positioned the measuring tape (I bought one of those cloth tapes you get for doing fabric work so it was tight all the way around the barrels) so the beginning of the tape was on the factory seam and marked the half distance then connected the two marks with a straight edge. I used a circular saw with a metal cutting blade to cut the drums. I started by cutting the bottom, then cut one side then the other cutting on the line I made and then the factory seam. I got the 2 24"x68" 16 gauge sheets from a local fab shop for $57. I used a hole saw to cut a 3" hole in the top of the black water tank and welded a 3" diameter piece of galvanized exhaust pipe into the sheet and then used a rubber hose clamped fitting to connect the welded pipe to the toilet ABS pipe. I also welded a 1" diameter threaded pipe fitting for a vent pipe and threaded on a connector to connect the vent pipe. Before I welded the fittings into the sheet I welded the sheet onto the barrels after welding the two pieces together.
The grey water tank was a little more tricky. I had to fabricate a recessed area for the shower drain trap as it extended 4" below the floor of the bus. I ended up cutting the pieces that I needed to create the drain trap box out of the lids of the barrels. I welded a 1 1/2" pipe threaded fitting into the recess for the shower drain trap to connect to and a 1 1/4" pipe threaded fitting for the sink drain to connect to. I also welded another 1" pipe threaded fitting into the sheet for the vent pipe for this tank. I joined the two vent pipes under the bus so I only had to put one vent pipe through the roof of the bus which I ran inside of one of the walls.
My 13 year old son and I held the barrels up under the bus to get the locations of where the pipes would need to be connected to the tanks. After everything was all welded I used 3 1-1/4" x 1/8" metal straps per tank to hold the tanks up and drilled holes into the angle iron that was already ran under the bus for the floor supports. I used grade 8 3/8" bolts to secure the barrels with the straps.
With a family of 6 we typically can go a week in the bus without needing to dump the grey water. This was the most economical way to install holding tanks that I could think of. If you have any questions feel free to post a comment below.