Is it possible or advisable to use schedule 40 PVC, the heavy white stuff, or CPVC, the beige stuff to construct the plumbing connections? These are both considerably cheaper than using metal parts.

I would like to know also

they're cheaper, but they tend to spring leaks and the valves that go with either one of them tend to break (handles mostly).

Mark

To be clear though, other than leaks and breaking valves, PVC is a viable alternative? Should I worry about chemical breakdown of the actual piping?

With prolonged exposure to temperature and the chemicals we use in this process, CPVC and PVC are not good choices. You would need to replace them regularly, and even then, you face the hazards from 2 issues. First possible hazard is a pipe breaking and dumping 10's of gallons of vegetable oil, methanol, biodiesel, glycerin, etc all over the place. God forbid your neighboors find out and and also contact the EPA. The second major hazard is a structure fire. It does not even have to be caused by the biodiesel processing, but just suppose the garage, shed, or house catches fire, melts the plastic pipe, and then WHOOSH!, it all comes running out during a fire. That endangers the life of firefighters and everyone else around at that time.

I know its tempting, but just say no.

Chris