## what is GPM flow rate through a 6" Schedule 80 at 75 PSI

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Richard
Posts: 5
Joined: Sun Dec 16, 2012 5:41 pm

### what is GPM flow rate through a 6" Schedule 80 at 75 PSI

I have a 6" sch 80 water line with 75 PSI, what is the GPM flow rate?. I'm installing a valve with a 3" ID on this 6" line. Does the GPM and PSI increase? What will the net GPM flow rate be? Thank you for any help.

Posts: 358
Joined: Mon Feb 08, 2010 7:47 pm

### Re: what is GPM flow rate through a 6" Schedule 80 at 75 PSI

To calculate flow rate you must know pressure drop - difference of pressure on the line start and on the line end. If line end is atmosphere than atmospheric pressure is the pressure on the line end.
You can use pressure drop calculator at: http://www.pipeflowcalculations.com/pressuredrop/

Also include valve resistance coefficient in calculator.
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Richard
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Joined: Sun Dec 16, 2012 5:41 pm

### Re: what is GPM flow rate through a 6" Schedule 80 at 75 PSI

Thank you for your reply. I don't know how to make the calculation. If you were to assume an open end line (atmospheric pressure) at 75 PSI, can you calculate the max rate of flow (GPM) for me? Also, what would the f/s velocity be at 75 PSI? I saw a chart showing over 5k GPM for a 5" pipe at 75 PSI and 12 f/s velocity. Again, thank you for any help.

Posts: 358
Joined: Mon Feb 08, 2010 7:47 pm

### Re: what is GPM flow rate through a 6" Schedule 80 at 75 PSI

You have to know pipe length and valve resistance coefficient K?
Do you also have two reducers 6/3" and 3/6" on the pipe for valve?
Do you have elbows, tees or other obstacles in the pipe line?
Geometry of pipe line must be known to calculate pressure drop.
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Richard
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Joined: Sun Dec 16, 2012 5:41 pm

### Re: what is GPM flow rate through a 6" Schedule 80 at 75 PSI

The application is a 6" line at 75 PSI which we insert an in-line valve with a throat diameter of 3" at the output of the water meter. The question posed is, will the 3" throat be able to provide the same (or close to) GPM rate. As for pressure drop, it would be variable, not knowing how many taps would be open at any given time. Can you make a calculation based on an open ended 6" line 10' long after the 3" throat is installed, how many GPM's would flow out the end of the 10' open-ended line. Wouldn't the GPM be the same as the 6" line without the 3" throat, just flowing faster?

I'm sorry I don't have the talent (or money) to figure this out, and I appreciate your help.

Posts: 358
Joined: Mon Feb 08, 2010 7:47 pm

### Re: what is GPM flow rate through a 6" Schedule 80 at 75 PSI

For 10' 6" pipe with 75 psi on the start and flowing out to 15 psi (atm. pressure) you have very high flow of 7000 gpm and velocity of 24 m/s or 81 ft/s so I think this is not a model you are working on.
If you put any obstacles in the flow you will have lower flow rate in the pipe and local flow velocity increase where contraction is, but after contraction velocity will come back to initial value.
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Richard
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Joined: Sun Dec 16, 2012 5:41 pm

### Re: what is GPM flow rate through a 6" Schedule 80 at 75 PSI

Thank you for your help and time. If at all possible, it would be great if I could speak with you directly so I may provide a more detailed description. My number is 813-837-1183. Thank you, again.

michaeljee
Posts: 1
Joined: Fri Jan 11, 2013 8:58 am

### Re: what is GPM flow rate through a 6" Schedule 80 at 75 PSI

Hi That is great, That is awesome information, i was also looking for this. please guide....Do you have elbows, tees or other obstacles in the pipe line?
Regards

Richard
Posts: 5
Joined: Sun Dec 16, 2012 5:41 pm

### Re: what is GPM flow rate through a 6" Schedule 80 at 75 PSI

Hi Michael, the admin answered the question that was posed to me. He was very helpful, and I thank him "For 10' 6" pipe with 75 psi on the start and flowing out to 15 psi (atm. pressure) you have very high flow of 7000 gpm and velocity of 24 m/s or 81 ft/s If you put any obstacles in the flow you will have lower flow rate in the pipe and local flow velocity increase where contraction is, but after contraction velocity will come back to initial value". Thanks again Admin.

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