J.C. wrote:

We got a propane heater the other day. The installation instructions call
for a "ground union" between the incoming on/off valve and the heater
connection. What's a "ground union" and what happens if I don't use one?

JC



That should read "ground joint union".

Look closely at a black iron (malleable) pipe union
and you'll see an embedded ring of copper or brass
which is carefully ground and polished to make
a leak-tight seal between the union halves.

http://www.fastenal.com/web/products....ex?sku=466343

Jim