What size of pipe for a water line from well to house?

[Erin]

Flexible pipe, probably. You know, the black plastic stuff.

How big should it be, running 900 feet from well to a 2.5-bath, 4-bed house?
One inch? Inch and a half?

[rick91351]

Erin I always use inch and a quarter.  Here on the ranch I keep a good selection of 1 1/4 fittings and clamps.  Tees - Elbows and Unions.  But you can not go wrong with inch and a half.  A lot less friction.   

[Erin]

Thanks, rick

[hpinson]

900 feet is a long run.  I see there are a number of online friction head loss calculators out there:

http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

Can someone who understands these work through an example with the 900 foot run of 1.25" ID black flexible poly pipe, and explain the results?

[Tome]

Flexible pipe, probably. You know, the black plastic stuff.

How big should it be, running 900 feet from well to a 2.5-bath, 4-bed house?
One inch? Inch and a half?

In the big picture the price between 1" and 2" is not that significant when compared to the labor and equipment cost to install.  2" sdr 21 with a gasket will give you a little flexing and would be my choice. It's available at most water works stores.

[SouthernTier]

900 feet is a long run.  I see there are a number of online friction head loss calculators out there:

http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

Can someone who understands these work through an example with the 900 foot run of 1.25" ID black flexible poly pipe, and explain the results?

The pressure drop depends on how fast the water is flowing through the pipe.

I made a post on this topic a while back going through the math:

http://countryplans.com/smf/index.php?topic=12608.msg167943#msg167943

Note, this was using the Darcy–Weisbach approach, which is referenced as an alternate approach to the hazen-williams approach referenced above.  The linked web page says the hazen-williams approach is accurate for Reynolds numbers above 10,000, but you may not have that high a Reynolds number for cabin applications.

I didn't rerun the calculation for 1.25", but my calc was for 1" and a flow rate of 2.2 gpm and came up with a pressure drop of 0.00215 psi/ft, or about 2 psi over 900 feet.  It would be less with a larger diameter