Step 3: Build the supply system
In this step, we'll assemble the propane supply system, which is responsible for taking high pressure propane from our supply tanks, regulating it down to a lower pressure, and storing it to be used by our flame effects.
When doing any plumbing with a flammable gas, it is especially important to make sure that each joint is sealed with properly-applied hydrocarbon-rated Teflon tape and that your system has zero leaks in it.
I used three 20# tanks with individual shutoffs chained to manifold with a pressure gauge. The gas then passes through an adjustable 50-135psi propane regulator and into the buffer tank, which has a second pressure gauge attached to it. The gas is fed through a ball valve and into a quick-disconnect coupler to make its way to the main accumulator tank.
A commonly-asked question: why did I use three 20# tanks instead of one big one? The reason for this is simply that it's all I had on hand - of course, a single 100# tank for the supply would have been optimal, but at the time all I had on hand were three 20# tanks. Using a single 100# tank would also cut down on the number of fittings required for the supply system, as you wouldn't need to run individual lines to each tank.
A note about using copper tubing to connect each tank: the copper refrigeration tubing is rated for pressures well above what you'll ever see in a propane system. However, copper tubing is very sensitive to repeated flexing of the line. Flexed enough, the copper will be weakened significantly and can and will break, releasing high pressure propane everywhere until the excess flow-limiting valve on the 20# tank kicks in. If you're using a 100# tank, you won't have this luxury. Ideally, you'd use high pressure propane-rated hose to connect each tank, although the ideal system wouldn't be using little propane tanks like this. Just be sure to limit motion of the copper tubing during use.