water supply line questions

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p_vavra

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Building my own home. I have to run water line from meter to house wish is approx 850'. Once I reach house, I would like to branch out to each side of property and run water lines for out building on one side and shop on the other side and the runs would each be about 100' or so. Others have told me that 1 1/4" pex would be OK for supply line but I'm wondering if 3/4" would work for my branch out water lines. Thanks
 

wpns

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850 feet is a long way, is it all on the same level? I'd go as big as possible, you really don't want to do it over later. How many people, how many bedrooms, bathrooms, etc? What's the water in the outbuildings used for? I'd do any branching out in the basement of the main house, so you can later isolate lines to the outbuildings in case you have a problem.

Back in the dawn of time my dad put a 3" line to our house, which was 350(?) feet uphill from the meter, but there were 8 people and a horse barn and a dog kennel and etc. Worked fine. 8*)
 

psklein578

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A 3/4 PVC pipe has a friction loss of 8.7 psi per 100 feet at a 10 gallon per minute flow rate. That size pipe will be a disappointment for an 850 foot run.
 

Twowaxhack

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A 3/4 PVC pipe has a friction loss of 8.7 psi per 100 feet at a 10 gallon per minute flow rate. That size pipe will be a disappointment for an 850 foot run.
He’s using 1.25” pex for the 850’ run. You’ll have about 22 psi drop flowing 10gpm over that distance.

So it depends on how much water he needs in the out buildings. These branch lines will be 100’ long.

The starting pressure needs to be known……Hopefully you’re starting out high…..no pun intended 🤡

It would be perfect if the starting pressure at the meter was 90-100 psi.
 
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Twowaxhack

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Back in the dawn of time my dad put a 3" line to our house, which was 350(?) feet uphill from the meter, but there were 8 people and a horse barn and a dog kennel and etc. Worked fine. 8*)
My neighborhood is fed with a 3” main 🤣, geezzzzzz
 

psklein578

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He’s using 1.25” pex for the 850’ run. You’ll have about 22 psi drop flowing 10gpm over that distance.

So it depends on how much water he needs in the out buildings. These branch lines will be 100’ long.

The starting pressure needs to be known……Hopefully you’re starting out high…..no pun intended 🤡

It would be perfect if the starting pressure at the meter was 90-100 psi.
Right, 1 1/4 PEX for 850 ft at 10 gpm would lose about 5.5 psi according to the chart I used. He could lose or gain pressure depending on the difference in elevation from the main. He needs to estimate how much maximum flow he will need and refer to a friction loss chart, figure in elevations and the pressure at the main. The size of the meter should also be considered.
 

Twowaxhack

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I used a chart by Rehau and they say 1.25” pex loses 2.4 psi per 100’ run at 10gpm.
 

psklein578

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I looked at the chart by Viega and it shows a friction loss of 2.3psi for the 100 feet of 1 1/4 pex at 10 gpm. That would be 19.55 psi for 850 feet of the pex. The other chart I used gave loss in ft. of head per 10 ft. Something was wrong with the calculations.
 
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