There is no reason you have to locate the cold manifold next to the hot manifold. They are not physically connected so can be located however you like. I do recommend a manifold system - it's nice to have one place to look for shutoffs.

You can use 3/4 PEX for the line to the manifold and then 1/2 or even 3/8 to the fixtures, depending upon water requirements and distance to the fixtures.

Best to use the crimp type in walls. Did you ask about the rings at HD? My local HD has them, but they are well hidden.

The manifolds I have seen are combo units (hot and cold together in a dual manifold). I suppose I could use separate units, but then if I want to turn off all water to one bathroom, I have to do it in two different places. Not a big deal, but not very convenient either. And the next owner of my home will probably think to himself, "what were they thinking?" (something I have often muttered to myself when I see how the previous owner did things).

No, I didn't actually ask about PEX fittings at Home Depot -- I suppose I could. Our local Lowe's is definitely special order only for PEX, and I don't go to HD much anymore because it's more crowded and more expensive than Lowe's (and since they are right next door to one another, it's just as easy to go to one versus the other!).

Another question came to mind after my initial post: should I have separate home-runs for every fixture (sink, bath, toilet), or one home-run per location (bathroom, kitchen)?

- Dennis

In that case I would place both hot and cold near the hot water heater. It is more accessible there. The manifolds I have can be installed together or separately and have 5 stations each. I actually have manifolds at each end of my house because, like yours, it is a long way from one end to the other. It made the installation considerably less expensive. I have a utility room on each end of the house though. I would not install a manifold in a crawl space.

Generally, a separate line (or set of hot/ cold lines) is run to each fixture. It is a much cleaner install this way with fittings at the manifold and fixture only, no fittings required in walls or other inconvenient places.

Thank you, that makes perfect sense.

So when I install the manifold, it will be in the garage with the water heater. But just because it's in the garage, I don't think I want a mass of hoses (10 cold, 7 hot) to be visible. How are manifolds typically installed...inside a wall with a service panel to provide access?

I'm assuming I will have to tear out sheetrock anyway, drill holes through a sill plate (not concrete, I hope!), and fish the hoses down into the crawl space to feed the rest of the house. So a new section of sheetrock in the garage is probably going to be necessary one way or the other.

How about the question of pipe size? I currently have 3/4" galv. for the main and 1/2" galv. to all of the fixtures. Is it reasonable to replace galvanized with same-sized PEX? Or will that result in a pressure loss? (strangely, a 1/2" PEX pipe will almost fit *inside* a 1/2" galvanized pipe!) I understand there are fewer couplings, elbows, T's, etc. with PEX, but is that enough to compensate for its smaller diameter? Perhaps it is enough, and maybe it's even necessary in order to increase the flow rate, but it's very hard to find good information on this topic, so I'm questioning everything!

Thanks again,

- Dennis

You can replace galvanized with same size PEX. Even though the PEX internal diameter is smaller, it is also much smoother and doesn't have elbows like the galvanized, so the pressure drop due to friction will be much smaller. It's like the difference between running your hand over teflon and running your hand over sandpaper. Which one will be smoother and faster? In addition, each elbow (and there are lots of them in a galvanized piping system) adds the same pressure drop as 5 - 20 ft of pipe, depending upon flow rate and pipe size.

Generally the manifolds are installed on the wall surface, not recessed into the wall. Installation in the wall may not be code(but I'm not certain). A shallow cabinet to cover it would work though.