In theory, the two flow graphs should be identical. In reality, they should be reasonably similar. As others have pointed out, the source of the water (purely gravity vs gravity w/pumps) and pressure reducing devices can really confuse things.
A few observations: a) Unless the flow is very high, pitot readings from a 4.5" outlet can be very wrong. On several occasions, I've seen hollow (literally) streams coming from the 4.5". When the pitot was placed in the center of the outlet, the reading was zero. To get a reading, had to move the pitot toward an edge. Got a reading, but it grossly overestimated the actual flow. b) If the 2.5' outlet flowed anything close to the combined sprinkler/hose demand, use those numbers. c) I wouldn't trust any pitot reading less than 10. If necessary, connect a smaller orifice to the outlet - the flow will be less but the pitot reading will be greater. d) a single-hydrant flow test is not recommended procedure, but if it can't be avoided, the results tend to be conservative. Curious - what are the exact numbers you're working with? Ed Kramer Littleton, CO > Have a question regarding hydrant flow tests. > > We have received a report where the contractor flow a single 2 1/2" > outlet > and gave us static, residual, pitot and calculated flow. He then > performed > another test using the 4 1/2" outlet on the hydrant, again giving us > values. > > Plotting the graph, is there supposed to be a correlation between the > testing of the 2 1/2" versus the 4 1/2" or are they supposed to be used > separately. For example, when graphing the 2 1/2" outlet, the 4 1/2" > outlet > info should be hitting this line or not?? > > Also, is a pitot reading of a range of 4 to say 8 on a 4 1/2" outlet > valid > data? > > We're not sure how to use this info. > > Richard _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
