Making an Optional Barrel
This webpage shows a very detailed build of the optional barrel mentioned in the External Tank & Venting webpage for those wanting a bit more detail.
In this example a 55 gallon white HDPE (plastic) barrel with two bungholes will be modified. First remove the two bungholes.
Now, drill out the small center section with a drill bit that just fits inside the recess. Notice the underside of the bunghole plug.
Now remove the side walls of the recess you drilled out so that it looks like this.
You can apply a sealant of some sort that will not be affected by various waste oils. Silicone would also be an option. Notice the large washer being held. The inner diameter of the washer should be large enough to let a 1/4" NPT pass through. In this picture, just a sealant was used. If desired, a flat rubber washer between the bunghole plug and the washer could be added.
Next a brass fitting (1/4" NPT by 3/8" compression) was inserted through the washer and then through the bung hole and was screwed into a 1/4" NPT galvanized pipe coupling. On the other side of the coupling a 2" long 1/4" galv. pipe was screwed in.
Next the depth of the tank was measured to the top edge of the bunghole. In this example it was 35 1/4"
Next, a value of 1 3/4" was subtracted from 34 1/4" height, giving a length of 33 1/2" - the length of 3/8" O.D. copper pipe that is being cut in this picture.
The copper tubing is then inserted into the 3/8" brass fitting end and tightened. This is the oil "feed" tube used by the pump to suck fuel out of the barrel. Then the assembly is tighened into the barrel using a bunghole wrench.
On top of this a 1/4" brass 1/4 turn ball shutoff valve is installed. The pipe wrench is used to keep the 1/4" galv. coupling from moving while tightening the assembly.
Once tightened the handle should be perpendicular to the front edge of the barrel as shown.
Once this is completed more 1/4" NPT pipe fittings are added as shown. In this example the fittings on the top left are 3/8" Hose Barb x 1/4" NPT. These type of fittings can be used to connect 3/8" I.D. (Inside Diameter) tubing. Later you will see that a couple of them were change out to 3/8" Tube Flare x 1/4" NPT for this particular application. The hose barb fitting on the left would be used to connect a fuel feed line from an external fuel tank source. The hose barb fitting on the right would be used to connect to a filter - like a 50 mesh stainless steel cleanable filter, before continuing on to the modified furnace burner.
Now, modify the second bunghole adapter. In this case it will not use a brass fitting underneath but a 1/4" NPT to 1/8" NPT reducer to allow returning fuel to dump into the barrel. Again, notice the large washer used. Otherwise the reducer could pull through the plastic when tightened.
Then tighten the assembly in the barrel.
Add a 1/4" brass valve like the other one on this assembly and tighten to the position shown.
Add the following 1/4" NPT fittings on top of this. Again, these 3/8" Hose Barb x 1/4" NPT could be replaced by whatever fitting is needed to connect to the type of tubing you desire to use.
Here's the final install of this barrel with 3/8" Tube Flare fittings as well as two of the original hose barb style fittings being used. In the configuration shown the furnace is running only from fuel in the barrel. The shuttoff valve for fuel return is open (valve on far left), the barrel feed line valve is open (valve on far right) and the external fuel source feed is closed (middle valve). The copper lines are connected to the furnace burner in this application.