Do pros solder shower valves before or after installing?

[petrie]

From watching online videos I got the impression that one should solder pipe stubs into a shower valve on floor and then attach it to framing so rest of joints can be made. Is this what pros do?

Since a shower valve takes so much more heat I'd be worried I'd be burning the mounting board if I tried to solder it in wall. But if you have two street elbows coming out the side of a valve becasue of a tight spot it would be hard to solder them on the floor and get the angle right.

 

[Terry]

It all depends on the situation.
If I'm doing a new installation, I normally prefab the unit. That way I can put the torch where I want.
If you need to solder in place, that's fine too. In some cases it's the only way.

I do pull the guts, and reinstall them when I am done.

 

[Sponsor]

 

[petrie]

Is it best to do all four joints at once. In a project I recently did I could have soldered pipe out of shower,tub and cold inlet on floor, and then installed valve and then soldered a street elbow in for the hot inlet, and then solder rest of joints. My concern was that I'd melt the solder in the other three joints trying to do that. Plus I figured If I was going to solder one joint with the valve in place I might as well do the entire thing, because getting one joint hot enough would practically get the rest of the valve hot enough to draw solder quickly.

Ultimatley I soldered the whole thing on the floor because I had never soldered a large valve before and I wasn't sure how easy It would heat. Map-pro and a bigger torch did the trick, though.