PVC Primer and cement question

How much time between applying primer and cement is acceptable?

Should cement be applied to pipe AND fitting or is one of them only okay?

All surfaces should be lightly coated. There is no waiting. First prime the section your are joining and then cement it.

I cement the pipe, then the fitting, and then hit the pipe lightly one more time before joining.

Keep in mind that a PVC joint is actually a solvent welded joint...the materials melt and when the solvent evaporates, they literally become one. The primer does several things: cleans any contaminats from the surface and starts to melt the surface and prepares it to be further disolved by the cement. The cement, by itself, may not penetrate the surface layer to make a good joint without the primer getting it started.

So, yes, you do need both the primer and the cement to make a good joint. In many places, the inspectors look for the characteristic purple color of the primer or they'll fail the installation. They do make clear primer, but it's not good in areas where the inspector is looking for the purple stain! (it is a lot neater, as a drip doesn't stain things, though).

I've read different things about whether the primer should be wet or dry. So I was wondering if I could apply primer to several joints at a time to speed things up and then cement them 5-20 minutes later.

Do one joint at a time. It is best if BOTH are wet when the joint is made. As stated in the instructions on the cans.