Best Plumbing/heating cad software?

Jellis

What do you ladies and gents recommend for a CAD program for light use. (would use a few times a year)
Any good free demo's?

ratio

I recently came across https://qelectrotech.org/, it's a drawing package that has hydronic templates, among other things. It's aim seems to be process documentation, including flow charts, wiring & piping diagrams, etc.

I wouldn't call it 'best'. In fact, I've found it rather hard to use (NB: only have a few hours of fooling around under my belt.) It is, however, free. The gallery shows some pretty docs, & if I'm understanding things correctly it'll cross-index ladder diagrams, one-lines, schematics, etc., all automagically. Primary development is in French, but there's at least one developer fluent in English, & the busiest developer is quite understandable.