"Jack" n wrote in message
news
I'm using type L instead of type M copper for re-piping my whole house
where only M is required by code. Mostly it will be installed in the crawl
space below a wood structure. Am I wasting my money or will it provide
better reliability say 20 to 30 years from now.
Around here M is not allowed. They require K for gas.

Reliability 20 years from now is not the issue; if everything is done
correctly and not subsequently damaged, either will be fine. It is just
that M will be damaged by things that don't bother L. (Sad but true, a year
ago I nicked a pipe while putting up a partition wall. Made no difference
to the L, but probably would have ruptured M.)

Even if your code doesn't require it, it seems like a good investment.