Hi Jeff,

I have an old steel water supply pipe and would like
to convert to PVC (and then to CPVC). I had cut the
steel line and used a PVC pipe "repair" (I don't
remember the proper name for that). That sprung a leak
on the steel side so I've replaced it with one for
steel pipe, this leaks on the PVC side.
What is the solution here?

Use a couple of pipe wrenches where necessary to remove the pipe back to
the nearest fitting (assuming you already cut the threads off the steel
pipe). In my experience, old galvanized steel pipe is usually rusted and
filled with corrosion (often down to just a pin hole), so it's very
possible the pipe or fitting will crack as you dissassemble it and you'll
have to keep removing pipe or fittings until you get back to something
solid.

Once you have a clean threaded fitting (or a threaded pipe end), pick up
the appropriate "transition fitting" from a plumbing supply or local home
center (Lowes or Home Depot). Basically, these have a brass fitting on one
side you can thread to your steel pipe, and a CPVC fitting on the other.
Then you can repair the plumbing with CPVC pipe as needed. Be sure to add a
few wraps of teflon tape on the threaded fittings before assembling.

By the way, according to code, you can only use CPVC for work inside the
building. Regular PVC is only allowed for irrigation or outdoor water
lines.

Depending on the age of your plumbing, you may fix one leak, only to have
another one pop up further down the line. This happened at my in-laws
house. After a couple of repairs, it was easier to just replace everything
with CPVC pipe.

Anthony