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# calculating pressure drop in a water line

Home Forums Public Forums General Plumbing calculating pressure drop in a water line

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• #273287
MasterPlumbers
Keymaster

I’m running county water to a new house. The distance tis roughly 4/10 of a mile. I was looking for a formula that would help me calculate the size of the line to give me the least practical pressure drop.

• #287297
SylvanLMP
Participant

Sure no problem

1- How many fixture units are you going to need? Flow rate (7.48 GPM)

2-What is the PSI requirement at the highest rated fixture?

3-Is this piping copper (type L, K, or M)? Is this brass pipe or galvanized or PVC or CPVC as we have to know the what the internal wall of the piping is so we can figure our friction losses by using the Hazen Williams formulas for piping and fitting take offs.

4- How high are we going to have to elevate this water as we need to figure pump horse power or available pressure (. 434 height) then add on the factor of friction losses through pipe and fittings AND the convert the PSI to feet on the fixture requiring the most pressure 2.31 pressure will tell us the height we will get
then we must make sure our velocity is not going to cause any erosion problems (not a concern with thermo plastics BUT with ferrous and non ferrous metals) BUT Plastic piping cannot take water hammering (Hydraulic shock waves)

I think you should at least give me a hint of the pH value of the water so WE can pick a piping suitable for this service.

Are we going to feed any sprinkler systems irrigation / fire suppression?

How many sprinkler heads as WE should figure the K factor into this piping design.

There is A fine OVERLY Qualified gentleman by the name of Bungie who is an EXPERT PLUMBER at this exact kind of design. I am SURE he could be of assistance with all the information you provided.

• #287298
Guest
Participant

There would be alot of time involved in your calculatig your engineering task, I can tell you that the street that I live on has 70 houses on it, the street pressure is 150 lbs and the line was 2 inch diameter , so to ease your mind You might call a plumbing company in your area and simply ask them what size line,theyb suggest installing for a 2112 foot water service , I would venture to say that they would suggest one and a half Inch for at least 1200 feet then one and a quarter for 800 ft then one inch the rest of the way, but as Sylvan suggests in what he says there are a lot of variables to consider , although you need at least 80 psi at the street or you may need to boost the pressure some where , also keep in mind that where I live you can run a 3/4 inch water service to serve a three bath house

• #287299
SylvanLMP
Participant

WOW MFranklin.

Do you realize that if your correct with the pressure and the piping diameter you have the following

1- A flow rate of 42.6 FPS (talk about EROSION and hydraulic shock HUH?)AMAZING “engineering”

2- This 2 ” pipe is pushing 42.6 GPM ASTOUNDING HUH

3- This pressure would elevate the water to a height of slightly over 346 FEET..A lot of fire departments would LOVE to have this kind of pressure and volume available LOL

I would love to see the 120 pound fire person holding the hose connected to this system LMAO

• #287300
Guest
Participant

its a beautiful day in the neighborhood, on top of that the county pipe is Blue poly,

• #287301
SylvanLMP
Participant

Blue poly doesnt have an ASTM number HUH? WOW is that like saying White PVC or yellow or red brass. I love the techinical responces we get on here so everyone can learn..

POLY WANT A CRACKER?