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Discussion Starter · #1 ·
Hello all, long story short the task of re plumbing an old, until recently abandoned, school has fallen to me. I'm planning to simply bypass the 90+ year old galvanized pipe and install PEX runs.

My question begins with the water main. Coming into the building is a 2.5" pipe. I'd like to install a new master shutoff ball valve and then T off to a few (likely diy) manifolds for PEX, I'm guessing this would be made out of PVC/CPVC.

Running PEX in anything more than a quick repair is new to me so I'm trying to figure out the best way to do this. Water heaters will be positioned throughout the building and I'd like to maintain at least 3/4" supply to them. Additionally in the interest of being neat and tidy I was thinking of running a supply branch to the water heater and another for cold to the same point. From there I could use manifolds to run local 1/2" tubing.

Does this sound like a good idea? If so, what should my supply size be? 1", or 3/4"? Then whats the best way to get to that from the 2.5" mains?
 

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first what does local code state? can you run pex in a commercial building? then how big of a school? you have to figure out some flow rates before piping..do the bathrooms have flushometers? they need certain size water supply to work correctly...more info is needed before you proceed ..are you a licensed plumber?
 

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Discussion Starter · #3 ·
State code specifies PEX as an acceptable standard for use. Local codes don't mention it. The building is around 45k sqft, 2 story. Current bathrooms do have flushometers, and I know the the min required supply for them is a full 1". However, with the building being abandoned for so long essentially all the the seals on the toilets are bad, mostly dry-rotted. In addition many of the pipe fittings leading to various fixtures leak badly. The building has froze several times before water service was disconnected.

All of the internal supply valves I can find are seized and are the old style gate valves.

I am not a licenced plumber, but the building is not now commercial. It's being renovated for personal use.

After the renovation is complete there won't be any large bathrooms like now currently exist and I'm planning on simply using new tank style toilets in the new bathrooms throughout the building.
 

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Does this sound like a good idea? If so, what should my supply size be? 1", or 3/4"? Then whats the best way to get to that from the 2.5" mains?
Ayuh,.... I'd think ya want 1" at the Minimum,....

Ya didn't say what the in-comin' line is, other than 2, 1/2",....
T it, reduce it, manifold it, whatever ya need,...
'n No, I doubt pvc valvin' it what ya want, but I ain't a Plumber,...
just a Diy'er that over-builds,....
 
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