We brought the system pressure up to 30 psi. The fact that it was holding pressure at all was a good sign. Just to check out how things were going this far, I cut the noisy air compressor off to have a listen. Sssssssss here and sssss there. Oh, and a sssss over here! Rats. We've got some leaky joints.
I was kind of expecting this, but I had also been holding out hope that we just might breeze through this test. No such luck. We marked the leaky joints with some blue tape and got back to soldering.
The first two joints were fixed with little trouble. After all, it was just two ends of a copper T. The third leak was a real hassle. First, we were out of MAPP gas and were back to propane, which burns much cooler. Second, this joint is a brass tail piece pointing downward. Third, it's only an inch and a half off the wall. I struggled with this joint for a long time - dripping solder on my bare legs (duh), nearly setting the moist rag on fire (I was wrapping wet rags around the mixing valve to protect its plastic parts), and having no luck. Solder wasn't flowing up.
I decided to remove the mixing valve completely, which was pretty easy since it's held on by three large nuts that grip the tail pieces. Then we removed the 6 inch piece of copper that goes from the T to the mixing valve. We cut a fresh piece, cleaned everything up nicely, and resoldered it in the vice. Lookin' good. Put it back in the T and soldered it in. Reinstalled the mixing valve and tested again - seems to be fixed!
That left two more leaks, both of which are where the PEX meet the brass, one atop a pump and the other above the manifold. We couldn't take care of these because we will need the crimping tool which is something that we borrow from the hardware store - and they were closed.
Before calling it a night, I needed to figure out, statistically, how we did with our first copper soldering job. We had soldered 38 joints and 6 of them were bad. 1 of which may be a faulty crimping, which isn't a soldering thing. About an 87% success rate. Not too bad. I guess we still deserved to eat dinner that night. So we did.