yes they are gate valves, I've soldered them before with no ill effects, but I go slow. I used to overheat EVERYTHING lol, you don't want to see my first attempts at soldering. I think there are still mounds of solder on the floor. I just priced copper today, sticker shock, $30 for a 10' length of type "L", $35 for 10' of type "M" (which is thinner, but costs more?!?) $1.90 for 10' of CPVC. Can I use CPVC pipe? I could probably sell a couple of the brass gate valves I have and plumb my whole system with CPVC pipe and it's way faster and easier but I always thought that PVC can't take heat.