You'd use the flow data you got from a nearby hydrant flow test. Typically I've not seen a ground tank that supplies a municipal system via gravity. In the municipal installations I've dealt with, a ground tank where there was no elevation difference had pumped supplies.
Craig Prahl | Jacobs | Group Lead/SME - Fire Protection | [email protected] | www.jacobs.com 1041 East Butler Road Greenville, South Carolina 29606 CONTACT BY: email or MS TEAMS -----Original Message----- From: Sprinklerforum <[email protected]> On Behalf Of Mark.Phelps via Sprinklerforum Sent: Friday, May 7, 2021 5:07 PM To: [email protected] Cc: Mark.Phelps <[email protected]> Subject: RE: [EXTERNAL] Re: Available Pressure from Fire Water Storage Tank So, if this same tank and pump were at the same elevation and 5 blocks away in a Water Utility Yard owned by the city water department, what pressure and flow rate would one use to design a sprinkler system? Mark at Aero 602 820-7894 -----Original Message----- From: Sprinklerforum <[email protected]> On Behalf Of Bob Caputo via Sprinklerforum Sent: Friday, May 7, 2021 11:21 AM To: [email protected] Cc: Bob Caputo <[email protected]> Subject: [EXTERNAL] Re: Available Pressure from Fire Water Storage Tank No, you are not permitted to use elevation pressure from a gravity tank. You do not know the elevation of the water in the tank which is depleted during the operation of the systems in fighting the fire. You are permitted to use the pumps productive curve at 150% of rated flow and 65% of rated pressure On Fri, May 7, 2021 at 11:13 AM Kyle.Montgomery via Sprinklerforum < [email protected]> wrote: > I'm working on a project where they are adding a new building to an > existing campus. There is an existing fire water storage tank and fire > pump that serves the site underground fire loop. The new building has > a very demanding sprinkler system that just barely exceeds the fire > pump's pressure available at the demand flow (using just the pump > curve as the water supply). > > Normally, I would be conservative and use just a few psi as my water > supply from the tank (as though it were nearly empty). But, is that > overly conservative? The tank is mounted on the ground, at the same > elevation as the fire pump, but it is nearly 45 feet tall, with a > total capacity of over > 500,000 gallons. Can I use some of that elevation pressure, or do I > need to design and calc as though the tank is nearly depleted? > > -Kyle M > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.firesprinkle > r.org_listinfo.cgi_sprinklerforum-2Dfiresprinkler.org&d=DwICAg&c=wn3mZ > QLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=sbcv > VKDiY86Z6_d0cmGpUAE-yKbUHdvwJfxJIwZih14&s=xW_3DXTpaglGRp_Lod9_4SygFCmo > JqtVkLeqtK_Eczg&e= > -- Bob Caputo, CFPS *President* *American Fire Sprinkler Association* p: 214-349-5965 ext124 w: firesprinkler.org <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.facebook.com_firesprinkler.org_&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=sbcvVKDiY86Z6_d0cmGpUAE-yKbUHdvwJfxJIwZih14&s=9_q6urq9zEQtQy7i4Nd_rk4BBZBOiJsNCVSFRpcdMjg&e= > <https://urldefense.proofpoint.com/v2/url?u=https-3A__twitter.com_afsa_status_1039528345367732224&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=sbcvVKDiY86Z6_d0cmGpUAE-yKbUHdvwJfxJIwZih14&s=PSOMCv00HpTP3bMjgG5Wczk2iOEH35yxgU-i0lh4kvM&e= > <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.linkedin.com_company_american-2Dfire-2Dsprinkler-2Dassociation-2Dafsa-2D_&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=sbcvVKDiY86Z6_d0cmGpUAE-yKbUHdvwJfxJIwZih14&s=4hyISelb176OLCvYsOKsSvSbu842IyJoPrQ706vZmVA&e= > <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.instagram.com_firesprinklerorg_&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=sbcvVKDiY86Z6_d0cmGpUAE-yKbUHdvwJfxJIwZih14&s=WnV3x7dwAvD344IBMMjlrMdRQMfoQ8YIBkyVCR4kNW4&e= > *Train a safer, more efficient workforce.* By enrolling your employees in the AFSA Apprenticeship Training Series for Sprinkler Fitters <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.firesprinkler.org_WWW_Education_Apprentice-5FTraining_WWW_Education_Apprenticeship-5FTraining.aspx-3Fhkey-3De88ef09e-2Dd74c-2D407f-2Dabcd-2D995aff866149&d=DwICAg&c=wn3mZQLIuInh2ClcJ0_DIA&r=dLwiR71i_XhSFqam3ZLeaFLiQJ3cDTUB0ReB4-yDDcg&m=sbcvVKDiY86Z6_d0cmGpUAE-yKbUHdvwJfxJIwZih14&s=_6Tmf4i1Euk-al8jqF5PF4JDRqcO13XAFZjt64gY110&e= >, you will reap the benefits of a qualified, professional installation crew. 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