Nelson Riedel, Nelson@NelsonsLocomotive.com
8/7/2010, last updated
The water tank is made of 1/4" thick Type 1 PVC obtained in 24" X 24"
sheets from McMaster-Carr. The sheets were cut using a plywood
blade in a table saw.
The tank overall dimensions are 21 1/4" long, 14 3/4" wide and 8 3/4"
high. The dimensions of the six pieces are:
An additional piece the same size as the ends was cut and used as a
baffle in the middle of the tank.
The finished tank inside dimensions are 21" X 14 1/4" X 8 1/4" which
has a capacity of about 10.5 gallons.
The first attempt at making the tank was to glue the sides and ends to
the bottom. The results were unsatisfactory in that there
were several large leaks and the joints seemed weak.
The joints were not of the strength one achieves gluing PCV pipe
fittings together. The major cause of the failure is
probably that the joints were not smooth and tight fitting.
The tank looked really good so went to Plan B and tried plastic welding.
Welding: The plastic
welding device shown on the right was picked up at Harbor
Freight (#96464) and a coil of 1/8" diameter PVC welding rod was
obtained from McMaster- Carr. For simplicity
I'm going to call the welding device a gun
The gun is connected to an air compressor for air and 115 volt AC
to power the heating element. The instructions say that air
should be turned on before the power is connected and left on after the
power is disconnected until the heating element cools. The gun
directs hot air onto the pieces to be welded much like an acetylene
torch. There are two adjustments, the air pressure/volume
and the heat control. After some playing with the device I
set the air for very low pressure --- probably only a couple pounds and
and the heat control about mid scale. With these settings and the
tip held about 3/8" from the rod the rod turns brown (singes) after 15
seconds or so.
I ended up welding both the inside and outside of the tanks.
The weld on the inside are corner welds. What worked for me
is to lay the rod in the corner, start heating from one end and use the
bent tool made from a length of 1/8" X 1/4" CFS bar stock shown in the
photo to push the rod into the joint. Holding the pieces during
this operation is a challenge. The ~ 10" length of large diameter
steel bar stock held the bottom in place and served as a vertical
surface to support the side. The top of the side will tend
to bend in much like welding steel. The operating is slower
then gas welding and it is possible to heat the pieces being welded to
the point where they begin to soften all the way through.
When this happens I just stopped and let everything cool down.
|This is a close-up of the joint in the
photo above. Note the slight singing at the upper end of
the rod. The scuff marks beside the rod show that the
surface of the pieces being welded were soft and marked by the
tool pressing the rod into the joint.
I used this technique to
weld the bottom, sides and ends together and then check for
leaks. There were a half dozen or so.
I went back and reheated the joints that were leaking and
pressed the rod into the joints again. This is were
I had some trouble getting everything too hot and the whole
joint turned soft.
|Once the inside was welded the outside was
welded. The next three photos are of a sample I did after
the tanks were all welded. The first step for the
outside welds was to cut a slight groove in the joint using the
Dremel tool. The joint was not as clean as shown in
the photo; the dust was cleaned off before taking the photo.
|The outside welds were made using a procedure
similar to the inside welds. About an inch or so of the
rod and joint were heated and then the rod was tamped in place.
A 4 oz ball peen hammer was used to do the tamping.
Photo shows the finished joint. Care was taken to move the gun
from side to side to make sure the pieces being welded were
heated along with the rod. The pieces being welded were
soft on the surface when the rod was tamped into the groove.
|The sample was cut about an inch from the end
to show the joint. It's as I had hoped it
After the outside of the tank was welded it was tested for leaks
again. There were several, mostly in the corners where three
pieces came together. Tamping the outside welds must have
broken the inside welds. Reheating and tamping the outside fixed most
the leaks. In one corner the Dremel was used to cut out a
length of the outside weld and it was welded again. That
One of the attractive aspect of using plastic for the tanks is that
standard plastic plumbing fittings can be attached to the tank for the
ports and vents.
Port: The input port was
made using a standard 2" PVC pipe with domed cap.
The cap was bored slightly to make it an easy sliding fit.
The 2" pipe OD is about 2 3/8". A 2 1/2" hole saw
was used to cut the hole through the steel outer tank and the
plastic tank top at the same time. (The PVC tank top had been
attached with a half dozen
screws sheet metal screws.) The oversize hole make the pipe a
easy fit up through the metal outer tank.
end of a 2" PVC coupling was glued to the end of a short length
of pipe that was to be the input port. About 1/4"
length of the upper side of the coupling was then turned in the
lathe to the exact diameter of the hole cut with the hole saw.
The lower end of the coupling was cut off leaving about
1/4" of the larger diameter to serve as a shoulder.
The upper end of the pipe was cut to the length such that the
end will be about 1 5/8" above the steel tank top.
The port was then glued to the tank top. It was later
plastic welded on the under side to make sure it stayed in
Ports: Two output ports are
required; an overflow which also serves as a vent and the output
port. Both these ports shown in the photo on the right use
1 1/2" PVC pipe. The pipe is about 1 7/8" OD.
The holes through the tank bottom were made with a 2" hole saw.
(The holes are over open areas of the tender frame.)
The vent on the right had a piece of
coupling glued to the bottom with the end turned to match with
the hole. The upper end of the vent pipe was cut off about 1/16"
below the underside of the tank top. The underside
of the vent pipe will be plastic welded for strength.
is the first photo to show the baffle which was welded in the
middle of the tank.
|Some years ago Dan Staron mentioned
that he would use a sump on his next water tank--- it sounded
like a great idea. A clean out plug threaded adapter and
plug proved to be an ideal sump.
outside of the adapter is about 2 1/4" diameter. A piece of pipe
was glued in the adapter and the end cut off leaving a little
over 1/4" length of the pipe end of the adapter with the pipe
inside. The last 1/4" of the outside of the pipe end was
then turned down to the exact diameter of the hole made by the
2" hole saw. The adapter was then glued to the tank
bottom. The top of the adapter is flush with upper side of
the tank bottom so all the water should make it to the
The square end of the cleanout plug is
hollow so a piece of the 1/4" PVC sheet was glued inside the pug
to give more thickness and a 1/4" NPT hole was then drilled and
tapped through the plug. (The output fittings use 1/8" pipe but
the 1/8" pipe threads looked too fine to hold in the plastic.)
The screen is a 50 mesh
McMaster part # 98755K11 Miniature PVC Suction Strainer.
The very end of the plug was bored slightly so that the strainer
would slide into the open end of the plug. It was then
glued in place.
The photos on the right
show the vent and the sump.
At this point the top of the tank is held in place by six screws.
A bead of caulk was run along the seam to make it watertight.
I'll probably scrape off the caulk and plastic weld the seam in the near