[John Rogers]

I had a shower fitting (brazed) start to leak after 25 years or so of southern CA bad water. I had already installed a whole house softener but the corrosion had already started. I tried working through a hole like yours and it was a tad hard so I made an access panel of the same materials as the shower. That made working on things much easier for sure. You might want to consider that and also a softener since you live in southern CA too?