Concern of water pressure on well for dual shower head setup

[AaronW]

I'm building a new home and the well is going to have a 3 and a half horse submergable pump. To get better pressure they are going to set the pressure switch at 40 to 60 psi setting with 1-1/4 in pvc going to home which shouldn't be more than 60 feet of pipe at most. I'm wanting to use the manablock system or some kind of manifold system. I can only find manifolds with 1/2" outlets and was wondering with a dual shower (one handheld shower and one rainhead) along with some kind of thermastatic control if a 1/2 pex line would supply enough water for both if both heads were rated at at least 2.5 gpm??? What would ya'll recommend

 

[Reach4]

How far down is your water? 3-1/2 HP is a big pump motor. It would be good to review before getting the pump.

I expect 1/2 inch PEX would not be adequate, but your thought of doing the hot+cold at bathroom makes it maybe doable. However bypassing the manifold for that load would let you run 3/4.

You might find this useful: http://www.uponorpro.com/calculator/

You could also consider 50/70 PSI for your water pressure if you ran 1/2 but the flow was not quite enough.

 

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[Jadnashua]

1/2" PEX would be marginal, if not dismal for a dual showerhead system. 1/2" diameter PEX for hot water should not exceed 5fps, which equates to 4gpm (this max water velocity also holds true for 1/2" copper designs, but the ID is larger, so you get a bit more flow). Depending on how hot your supply is and how cold the cold input is, with Federal mandated max flow showerheads (2.5gpm max * 2), you would be exceeding both the maximum recommended flow rate on the hot side most of the time, especially in the winter when you won't need much cold to temper the output. On the other hand, 3/4" PEX can flow about 8gpm at the same 5fps velocity. That r-squared factor really makes a big difference with a small diameter change! For most other things in the house, 1/2" pex is fine since they are mostly flow restricted. For things like a tub, multi-head shower, and outside hose bibs, larger supplies can be useful, otherwise, smaller is fine.

While pressure is important, it's more about volume. Fire hose verses soda straw...bigger is better for maximum flow and less line friction (and resulting pressure losses). Many people live quite well with 40psi supplies.