I'm in the Kansas for the weekend visiting family and my dad was talking about redoing the plumbing in his basement. I thought I would post his situation here to get some advice.

The house was built in 1933 and was originally all galvanized. Over the years, parts have been replaced with a mixture of galvanized and copper. It looks like each time there was a need to change/reroute or add a plumbing fixture - whoever did the works chose the easiest (not always correct) way to do it. There are tees to nowhere, soft copper that has been rolled over as a stop, runs that go from 3/4 galvanized to 1/2" copper and then back to 3/4 galvanized. 3/4 lines teed off of 1/2 lines. Plus, it looks like the pex spaghetti jobs I've seen in the past - just in galvanized and copper. In short, it's a mess. Lots of pressure/temperature drops.

My dad's plan is to take some time this fall and redo and clean up what he can. If he could, he would just start over - but there are two longer trunk/branches that run from the basement to the second story behind tile walls he doesn't want to have to rip out. There's also lots of good copper that doesn't need to be fully redone either.

Most of the 1/2 copper lines in the house run back to the basement. It would be easy enough to cut out the bad/unnecessary piping and tie the existing copper back to a manifold. However, there are two second story bathrooms that have new 3/4 copper running directly from the basement. These have branch manifolds at the bathroom feeding the fixtures. There is no reason to replace these...I hope.

So finally - my question.

On the hot water side, if we put a manifold after the water heater to feed the 1/2 lines for individual fixtures, should we tee off before the manifold to feed to the two 3/4 lines that run to the second story? Or would it be better to continue through the manifold and tee afterwards? Or does it even matter?

I've attached two pictures to illustrate the ideas.

The cold side would essentially work the same way. Manifold that ties into the existing 1/2 lines and then tie into the existing 3/4 cold line to the second story.

Or, is the approach just a bad idea all around?

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