I always hate threads where lots of suggestions or troubleshooting go in and yet you never hear the outcome. Although things get busy at times I always try to get back to it... eventually.
Besides, it's always interesting to know who guessed right, even if sometimes the same issue could have different solutions.
It's on the way at least.
Have you considered being a prophet? People sacrifice nos olds parts to you for some wisdom?
This house was supposed to be several things... but what's its become is an effort to get it back up to par.
A toilet just got replaced because the intank valves went fubar, and, coincidentally, both the upper tank bolts oxidized beyond any separation without porcelain damage, the wax ring was bad, and an upgrade cost $68 for a complete kit - tank, bowl, mechanicals, ring, seat, etc. Cheaper to replace with better than repair heavily corroded parts.
So we've been blowing clear various lines, changing various filters. It doesn't have one of those whole home filters of the type you suggest, although that would be smart.
Also changed/removed were a water filter on a shower head that clogged itself, a couple branded lines, and a damaged faucet.
Most recently, the hot water faucet at the sink furthest from the water heater is putting out cold water, every other faucet working properly. So there's a cross-over issue going on, although there is no laundry equipment which is often the source. Could be a tub/shower valve, but, it's a half bath so you'd think the sink nearest it would show that issue. Never know pipe routing though.
There's still an unknown water filter system under the kitchen sink and looking into the dishwasher to consider. The rest are, for now, starting to be sorted and falling into place.
So, household water plumbing has advanced through 101, 102, 103 to course 104.
