Renovation, all new plumbing questions

I am renovating a very old house that I live in. Plumbing is in the CRAWL space under the house, a very small tight crawl space. Drain lines were broken when I moved in and new leaks and breaks every couple months or so. House was built in the 40's, plumbing and electrical look way older than that if you ask me. Most of the drain lines are lead and the P traps are old school, look kinda like large coffee cans. Since I'm under the house already replacing drain lines, I would like to go ahead and replace supply lines. I know the house has a .75" or " PEX supply line from the meter to where the break was just inside the crawl space. At that point it connects back to the origional steel suppley line. The supply line has branch lines running to the cold water faucets (toilets, showers, and washer) before ending up at the water heater. Same for the hot water side leaving the water heater. It branches off to the needed hot water faucets.
My question is if this is the best way to run the lines when I replace then. I've seen instalations where they use a manifold type connection with multiple ports that feed everything from that central location. Or is the branching off the supply line a better way. Or is there an even better way of doing this that I might not be aware of?
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A home run system is cool, but it can require running a lot more tubing and also requires a manifold which aren't exactly given away for free at plumbing supply stores. I've never heard that they are better except you can turn off fixtures at will from the manifold. Since you have a crawl space, you'd also need some sort of mechanical room to locate the thing. IMO you are better off with a traditional system.
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Well I am relocating the water heater, furnace, washer, and dryer to a utility room which could also be a location for a manifold. But if thats the only pro to having one, I think I'll go traditional. Also I'm just trying to avoid problems like getting all cold water in the shower if someone uses the kitchen sink or flushes a toilet. I'm guessin the manifold would also use alot more pex tubing since all runs would have to be a home run to the manifold.
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If you replumb your house with properly sized supply lines this will be less of a problem. A pressure balancing shower valve is also a good thing.
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go with manifold no joints, you can make a manifold by using pex sections
better flow, easier service, pex is cheap, no Ts in inconvenient spots..
temp shower valve is well worth the expense and still a good idea even with individual lines
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What do you mean by no joints? All of the pex I see going into new houses has as many 90 degree ells as copper did, practically. You really can't crank the stuff around a corner..you have to put a 90 on it. I'm also wondering why you say better flow? Do you know this from experience?
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marson wrote:

From what I've seen, they don't use 90 degree fittings, they use plastic clips that hold the PEX in a 90 degree sweep, and this would indeed give less flow resistance than a "hard" 90. Perhaps the ones you've seen are installations by "old school" plumbers who haven't quite adapted to the new technology.
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No I work for a builder, so I see a lot of plumber's work. We have three different plumbing contractors that we use. They are not old school. I see 30 year old plumbers putting them in on every house I work on. I haven't seen someone using bend supports once, except when something is going to get buried in concrete.
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marson wrote:

Don't know, perhaps they make more profit by using more fittings and connections than necessary. Certainly the manufacturers of the PEX don't recommend that.
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we looked at probably two dozen houses while house shopping with our son. All the pex jobs i saw had the 90's clamped on them. And 'tee's' also.
s

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I thought the whole point of using PEX was to eliminate as many connections as possible, particularly ones inside of walls where the mechanical seals could leak unnoticed for some time. This would rule out Tees and Ells and promote home runs from a manifold and using curved tubes to make 90 degrees.

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EXT wrote:

I certainly though that was supposed to be one of the big advantages, coupled with the flexibility that allows you to fish it continuously. Exact same idea as the flexible stainless gas line that's beginning to replace the old black pipe with all it's potential leak points.
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perhaps the new pex doesnt have plumbers retrained properly yet.
pex is supposed to be ran in home runs, which gets better flow.
Tees tend to split the flow and thus reducing it.......
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Next time I see a plumber running pex with fittings, I'll ask him about it and let you know.
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My current home (1930 1 1/2 story; two ~stacked baths, laundry room & kitchen) was re-plumbed with a home run system (valved manifolds).
I looked at it both ways & to me the home run system seemed best. Yeah, it used more tubing but way fewer connections & no fittings except at the fixtures & the manifold.
The stuff is pretty flexible (not like a garden hose but way more flexible than soft copper) easy to snake thru walls, ceilings & thru sills.
I like the home run method; continuous runs from manifold to fixtures, not connections to make or leak along the way.
For a larger or spread out home, a traditional branch & main might make more sense.
OR
a hybrid system with some branch circuits & extra remote manifolds.
The home run system makes instant hot water loops harder to implement but if the layout is compact & the tubes are sized right the wait for hot water will be short even without a hot water loop.
The longest wait I have for hot water is ~ 30 secs & I waste less than a gallon.
cheers Bob
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