Thanks Jeff, Wayne, Terry, and James - I appreciate all the help working through this! I really need to do something for you guys when I get through this.
It does sound like the service is the issue, and I'll have to treat it individually. the house is large, which is why I will rent out part of it. Some houses may have a lot of users; in this case usage would be 4 people + 1 renter in the furthest end. Point being, I'm not likely to have have 4 showers running concurrently with a line outside the door.
The overall project is also big... I'm rebuilding about 50% of the house, and doing about half the work myself, including things like design and install of the radiant heat system, electrical, etc. A bit too much with a 55hr a week job and family, but have to keep shoveling! Multi-year construction living, not much sleep.
I've had most of the L copper for over a year now, so the main house will be copper, and I am using viega propress. Far-end and radiant with Uponor ProPex. Agreed on sizing, quality materials and getting it right with good design and workmanship.
To clarify... when you say coming in house with 1-1/4 or 1-1/2, you are saying 1-1/4+ on the interior of the home, to the mechanical room (where it branches)?
If so, that would match with what I was tallying up as WSFU's.
For overall house, using the guidelines from 2015 IPC, I get:
Using 'Bathroom Groups' (supplemented for additional Lav's, etc)
Hot/Cold/Combined WSFU's
28/16/36
Alternate approach of tallying all fixtures individually would be:
35/18/41
Sec 201 doesn't reference using E103.3(3) to then find GPM, but it the only way I see to get to GPM. If I use that, it says 36 WSFUs = 25 GPM for the main distribution pipe (hope I am using that term right) in the house. Assuming max copper velocity of 7 ft/s (cold), that would give 18GPM for 1" type L or 26.6 GPM for 1-1/4" type L...
so IPC sizing would be for 1-1/4" on the main distribution pipe leading to the mechanical room. Which matches what Jeff suggested.
Does this sound right and typical for a 4-1/2 bath home with a few extras (2nd washing machine, etc)?
Terry, thanks. I had been studying your page on that earlier. Something funny is up here, in that 1 WSFU doesn't appear to be universal. In your version, things like water closets, showers, washing machines are dramatically different WSFU's:
2015 IPC:
And the water supply line sizing table seems to use different units, too (so it is not just about low-flow fixtures).
50 - 60 psi, 3/4 meter, 1" Distribution Pipe, 400' = 9.5 fixture units, not the 17 that your chart shows.
Maybe yours is a different standard, such as UPC, or maybe they changed the definition of a WSFU between the time you took your table, and the 2015 IPC?