Before the largest of our water purveyors went with models about twenty points were selected at which the fire marshal’s office conducted flow tests in the field. Maybe one per 2 sq miles (?) to give some idea of scope. Not distributed evenly of course. This check on model’s accuracy was probably invisible to the sprinkler designers.
Best. Bruce Verhei > On 08/31/2022 9:35 AM Steve Leyton <[email protected]> wrote: > > > I respectfully, but stridently disagree. To this comment and Rick’s > overarching question, I would offer that our experience over the past 10+ > years has been that these models are not only accurate, they are highly so > and can be programmed for eventualities and conditions that flow tests simply > cannot reflect, because they are a measurement of the “right now” only. But > I would offer an bold asterisk on my comments because they are based on > regionality and I’m in the SWUSA, where water management has been a critical > thing for a full generation now. > > Because of drought concerns going back 20+ years, many water agencies stopped > doing flow tests and began to meter their systems. Today, nearly all water > agencies in California will only grant a permit to do a physical flow test if > there are compelling circumstances, and we rely on models. Using San Diego > County as an example, water districts began installing sensors 25 years ago > and have been collect metadata on overall system performance for dozens of > years; these systems are in fact predictable if the database used to > calculate performance is well-populated and highly detailed. I was going to > offer Rick the anecdote of how we designed a whole campus high school 15 > years ago, in a subdivision that was brand new. The only “flow data” we had > to work with was the master developer’s civil engineering water study, which > was based on the zone model from the water district. And it said that the > static was going to be so high (182) that we needed to install pressure > reducing valves on the supply side of the backflows feeding the site loop. > We also used the model for sprinkler hydraulics, but corrected the pressures > downward for the PRV settings. When the permanent system was commissioned > into service (two years later and with sprinkler systems 80-90% installed) > the static pressure was 181 and the residual was exactly the same as modeled. > > Programmability of models enables simulation of worst-case scenarios, > particularly peak day demand, annual drought predictions and legacy drought > conditions. This is extremely important in the West as our water levels are > literally dropping every year, so maybe that’s why our water agencies have > established such high standards of care for modeling. City of San Diego > doesn’t require that you take 10% off of their models any longer – why? > Because they program peak day demand, legacy drought levels and an additional > safety factor. When they first started this practice, the FP community was > going nuts – field conditions showed 10-20 PSI more pressure at the hydrants > in some cases. Yes, pipe sizing was affected, but if we’re talking about > safety and prudence (without consideration for the cost-impact, obviously), > this methodology yields solidly conservative data for basis of design. > > Chains are only as strong as their weakest link and physical flow testing > only reflects current conditions. Was the test done during a peak day demand > window? Was the test measured with a $10-15 spring loaded gauge (up to 8-10% > error) or a calibrated liquid-filled one with a 1% error or less? Was the > test even taken by skilled personnel? My opinion on this has swung – I’m > now pro-model and we look at physical testing as an archaic practice, and I’m > a shamelessly analogue Boomer. > > > Yours in the name of fire safety and progress, > Steve L. > > > > From: Prahl, Craig <[email protected]> > Sent: Wednesday, August 31, 2022 8:10 AM > To: Discussion list on issues relating to automatic fire sprinklers > <[email protected]> > Subject: [Sprinklerforum] Re: [EXTERNAL] Hydrant flow tests > > Having experienced bogus results from computer modeling on more than one > occasion, nothing matches the actual flow of the hydrant systems. > > Most recently I got a water report from a local municipality who generated > the info via their water modeling software. It said I could expect 6700 gpm > from the system……. via 8” lines at 10 fps! Nope, don’t think that’s going > to be a real thing. > > Craig Prahl | Jacobs | Group Lead/SME – Fire Protection | > [email protected]<mailto:[email protected]> | > www.jacobs.com<http://www.jacobs.com/> > 1041 East Butler Road Greenville, South Carolina 29606 > CONTACT BY: Phone 1-864-676-5252, Email or MS TEAMS > > > > From: Rick Matsuda <[email protected]<mailto:[email protected]>> > Sent: Wednesday, August 31, 2022 9:51 AM > To: > [email protected]<mailto:[email protected]> > Subject: [EXTERNAL] [Sprinklerforum] Hydrant flow tests > > I know that an accurate flow test is critical for the sprinkler system > design, but I’ve heard several discussions recently about water conservation > during our drought conditions across the SW states. > > With all our technology, is it possible to develop an accurate computer > modeling program for water departments to use in lieu of flow tests? Even > with the program, I think there would still be a need for some flow tests to > verify the program results, but maybe not as many as now. > > I’m not taking any pro/con position regarding this issue. I’m just providing > food for thought for the future as our need for water increases and our > resources diminish. Adequate water is the key for our industry. > > It’s ironic cause we get more wild fires due to the drought, and then we have > to use more water to fight the fires. > Rick Matsuda > > > ________________________________ > > NOTICE - This communication may contain confidential and privileged > information that is for the sole use of the intended recipient. Any viewing, > copying or distribution of, or reliance on this message by unintended > recipients is strictly prohibited. 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