You're asking an open ended question. Sorry for running you around in circles.
There are too many unknown variables here that are needed to make any kind of determination. Like has been said, how much pipe, fittings, valves, elevations, what kind of discharge gpm, etc. etc, etc. Plus the value at what tank level, since the tank head will affect the residual pressure. If you go by the flow required to produce a 10 fps velocity out of NFPA 24 for instance, that flow rate for an 8" would be 1560 gpm. If you use cement lined DI pipe at 1560 gpm the pressure drop is .156 psi/10ft. Ina real simplistic format, if you had 20 ft of pipe, static of 70 psi, flowing 1560 gpm, the line loss equals .313 psi. Use 1560 gpm and 69.6 psi for the K-factor which comes out to K=197.8. Naturally the gpm will be slightly less than at the discharge but that difference would be negligible at these variables. This is all nominal since like I said the value will vary depending on tank level and other unknowns. Craig L. Prahl, CET Fire Protection Specialist Mechanical Department CH2MHILL Lockwood Greene 1500 International Drive PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 [email protected] http://www.ch2m.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Greg McGahan Sent: Thursday, August 06, 2009 9:37 AM To: [email protected] Subject: RE: water storage tank Guys, I know all of the basic hydraulic stuff....I do NOT know the K factor of an 8" open pipe and don't feel comfortable guessing at formulas. I went to college and I know there is a formula that will easily tell you a reasonable expected flow and pressure. Bu that was a long time ago. Greg McGahan Operations Manager Living Water Fire Protection 1160 McKenzie Road P.O. Box 877 Cantonment, Florida 32533 (850) 937.1850 | Fax (850) 937.1852 | Cell (850) 554.3231 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, August 06, 2009 8:29 AM To: AFSA Subject: Re: water storage tank That depends on flow rate Greg. Higher flow = higher loss per ft. Longer run = higher loss at specified flow rate. Sent from my Verizon Wireless BlackBerry -----Original Message----- From: "Greg McGahan" <[email protected]> Date: Thu, 6 Aug 2009 08:06:45 To: <[email protected]> Subject: RE: water storage tank I know the static pressure. I need the RESIDUAL pressure and flow through an open 8" pipe at ground level. Greg McGahan Operations Manager Living Water Fire Protection 1160 McKenzie Road P.O. Box 877 Cantonment, Florida 32533 (850) 937.1850 | Fax (850) 937.1852 | Cell (850) 554.3231 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, August 06, 2009 7:28 AM To: [email protected] Subject: RE: water storage tank The formula is: ft of water x .433 = psi So for 140 ft of head the approximate psi would be around 60 psi, at 70 ft it would be approximately 30, etc. Note that this does not account for the loss through the tank outlet, vortex plate valves or piping loss. Find out what that 8" is. Especially if it's a plastic. Beware of HDPE. Craig L. Prahl, CET Fire Protection Specialist Mechanical Department CH2MHILL Lockwood Greene 1500 International Drive PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 [email protected] http://www.ch2m.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Greg McGahan Sent: Thursday, August 06, 2009 8:18 AM To: [email protected] Subject: water storage tank We have a situation where a new water storage tank is being installed on a public utility system and I need some help if anyone can tell me the following: New Tank - 140' high 8" pipe (unknown type) going straight to ground level What is a reasonable expected flow and residual pressure? Any help would be appreciated. Greg McGahan Operations Manager Living Water Fire Protection 1160 McKenzie Road P.O. 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