|Tanks for the Memories!
ABS plastic can be had in
various thickness in both food grade (white) and regular (black). I used white for the
fresh water tank and black for the holding tanks. The white was about $10.00 more per
sheet. It comes in 4' X 8' sheets. I used 1/4 inch thick sheets. First, figure the size
and shape of the desired tank and purchase the required amount of material.
Cutting was done on a table saw using a 80
tooth carbide blade. A course (80 grit) sanding block can be used to true up an edge or to
smooth as necessary. (I found that I had to do very little of this.) Gluing was done using
the "water type" cement.(This is basically a solvent and melts the plastic that
then bonds or welds itself together.) You get a squeeze bottle with a needle (like a
hypodermic needle), fill it with the cement. Put the two edges together such as a side
wall setting on the bottom, Press them together, and go along the "seam" with
the squeeze bottle needle. I became very inventive on items to use to hold pieces in
place. I used socket sets, tool boxes, and any other item that would balance and give the
required weight. It helps if you have a flat surface to work on.) The cement will flow
into the seam by capillary action and within about 30 seconds will be bonded. I usually
let it set for an additional 15 minutes before moving it. If you have to make a butt
splice, I put a doubler on the inside to give more strength. All of these materials should
be available at the plastics supplier. I recommend going to a warehouse or commercial
supplier, not to a hobby store.
You can bend this stuff so you don't have to
make as many cuts and glue. When I did it, a commercial heater (a calrod unit) cost about
$200 - A hobbyist heat strip about $25. Difference is - with the commercial, takes about
15 seconds to heat enough to bend; with the hobbyist, about 5 minutes. You can guess which
one I used.
For connections to the tank, I glued a doubler
to the inside of the tank where I wanted the fitting. For the water, I drilled and tapped
the hole for 1/2 inch pipe and it has yet to leak. ON the fresh water, I have a drain,
outlet to pump, & vent, all 1/2 inch. The filler is standard 1 1/4 inch RV filler. On
the holding tanks I have the outlet glued to the bottom, and for the inlets - used the
rubber connectors for 3 inch and 1 1/2 inch pipe mounted in the cover. Vent is 1 1/2 inch
pipe also in the cover.
Back to the construction of the tanks: The
fresh water tank is extensively baffled because I have it mounted on the bottom and the
two 90 gallon holding tanks sit on top of it. The baffles make approximately 20' squares.
In the top and bottom of each baffle I
made a 3 " diameter half round; Bottom for water flow and top for air flow. I figure
that the flow of water either in or out of the tank will not be so great that those
passages would not accommodate. The Black water tanks has very few baffles, mainly
triangular braces on the walls to increase stiffness. Being a devout coward, I made
1/4" X 1/4" strip out of the left over material and reinforced all of the glued
joints by gluing these strips on the inside. Then being truly devout, I covered these
joints with a "heavy bodied" clear cement. After construction, I filled each box
with water and let it sit for several hours to confirm no leaks.
Around the inside top edge of each tank, I
glued a 1" wide strip as a doubler into which I could drive screws. I fitted the top
into place and drilled a countersunk pilot hole into which I drove 1 inch #6 dry wall
screws spaced about 3" apart. Once I had everything ready, I placed a bead of
silicone on the edge and placed the top in place and screwed it down. I feel that this way
I have access to the inside of the tanks if needed. I built these tanks, I believe in 1991
and have had no problems with them.
Why do I have the holding tank above the water
tank? These tanks are in the rear baggage compartment of my 4106. The holding tanks
overhang the water tank by 12". This allows the dump valves to be located inside and
protected so they are not hit by anything and also I don't have to crawl under the vehicle
to hook up to dump. Just open the door and there it is.
My fresh water tank is 48 inches wide by
approximately 64 inches long and 11 inches high. (144 gallons) The holding tanks are five
feet wide (so they over hang the water tank) and combined, the same length as the water
tank. My holding tanks are trapezoid shaped because with rectangular tanks the toilet
would have dropped between them. The nested shape are rectangular.
George Lowry with comments or questions.
Posted on Coach Conversion Central with permission of the author.
Thank You! - George