Water flow through pipe

LarryC_4

What is the discharge pressure?

I'll give you one flow rate, at 95 psi discharge, flow rate equals 0 gpm.

Larry C

Edward A. (Ed) Carey_3

Need help with a water flow question

I need a chart or formula to estimate the approximate flow of water in GPM through a 3/4" copper pipe that is 30 feet long, at a 95 psi water supply pressure. There are only a few fittings. I can calculate them in as is needed.


Thanks

Ed

RJ_4

Bell & Gosset System sizer wheel. Check there Web SIte. Remember water flows when there is a differential. You stated 95 psig this would be your static pressure.

Edward A. (Ed) Carey_3

Flow from pipe

Thanks for your replies. I think that I did not provide enough information in my original question.

I am looking to calculate the estimated GPM flow of water out of the end of an open 3/4" copper pipe that is approximately 40 feet long, and connected to a water main that is operating at approximately 90 to 100 lbs pressure.

I am looking for a chart or a formula to calculate the estimated (expected) GPM flow out of the end of the pipe, and be able to know the estimated change in that GPM flow if the other known factors would change.


Thanks,

Ed

Carl_20

Flow rate

Carl_20

Flow rate

The formula no one seems to want to help you with is:
Cv = GPM divided by the square root of the pressure differential. Meaning, your 3/4" pipe has a Cv (flow coefficient) of about 24 to 28. Therefore, to get your gpm or gallons per minute of flow, you multiply say 24 times the sq. root of your pressure diff. What's that? You have 95 psig coming in but how much are you losing or how much pressure is being dropped due to friction, bends, coils, faucet flow restrictors etc. You'll have to guess at that number. So let's say you drop 50 psi. You would subtract this from 95 and get 45. Take the sq. root of that and you get 6.708. Multiply this by 24 and you get 160 gpm. Seems like a lot and it is. That's because you would drop a lot more across a faucet at this input pressure. My guess is that your faucet manufacture will suggest putting on a water pressure regulator to get that pressure down to around 50 to 55 psi at most otherwise you'll damage the faucet and also over pressure your hot water tank etc. etc. Hope this helps

Unknown

Not into

sq. roots and all that, but here`s a "Fred Flintstone" way sometimes used for well pumps.

Dave

zeke

Basic drop equation

It's little bit more complicated than indicated since you aren't designing this pipe.

First off you need to write the basic pressure drop formula"
f*l/d*V^2/64 where

f is the friction factor (that is complexly determinsd from the diameter, roughness, viscosity and density of the fluid)
l= equivalent length of pipe in inches

d= diameter of pipe in inches

V= fluid velocity

Since we know the pressure drop-95psi,95*144/62.4= 219 feet of head we can write the equation

219=f*40*12/.75*V^2/64 +V^2/64 (note the additional term is the loss at the output)

I first assumed a friction factor of .02, getting

V=35 feet/sec and
flowrate =60 gpm

I then checked the assumed f=.02 by getting a Reynolds Number*, RE, and determined a more accurate f= .017 which, after plugging it in would increase the V slightly, so .02 is a fair estimate.

* RE=VD/mu

V ft/sec

D dia in feet

mu = kinematic viscosity, FT^2/sec

RJ_4

Is this line a city water line piped into a water meter?

hot_rod

How long would the copper last at

35 feet per second flow rates, I wonder? Seems like the erosion corrosion would be a big factor. If the water had any deposits the life expectancy would be fairly short.

A 90 ell may turn into a heel outlet fitting within minutes.

I've seen somne big flow rate numbers like that in fire sprinkler design. But it may be only a one time use

The CDA has some flow rate tables but they limit to 10 FPS and a 30 gpm flow rate at that velocity.

hot rod

Weezbo

it might be best to add a few more ideas to the mix...

with a well that produces 8 gallons a min.....you can meet codes using 3/4" within 30 ->50 psi.....for small homes with less than 19 fixture units under 2 stories in height and less than 200 ' of developed length....most likely.

i have owned a hydraulic pump that you could likely run the pipe to destruction...

at 95 psi.... the faucets and valves might not like you much for sending 95 psi at them even at 8 gallons a min. many residential shallow wells produce around 5 -> 8 gallons a min.