I'm quite familiar with conducting hydrant flow tests, NFPA 291, and have read articles such at the Sprinkler Age article from Feb. 2018. And I know the residual hydrant should be between the hydrant(s) to be flowed and the large source mains for the area.
But in terms of a specific project site (especially if the underground is well-gridded), would you chose the hydrant closest to your project to be the static/residual hydrant, or would you select the flowing hydrant to be closest to your project (and adjusting the static/residual for any elevation difference)?
Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
3/24/2022 08:08:16 am
Sounds like you're pretty familiar with 291, which is good. I've kicked flow tests back to field crews because they did it wrong more times than I can count.
3/24/2022 08:10:07 am
From the Appendix of NFPA 13:A 24.2.2 (2016 ed)
3/30/2022 10:59:25 am
Great response from James P. here and correlates to Jesse's response.
3/24/2022 08:12:57 am
One thing that I have done in well-gridded systems is to shut off a valve and perform the test towards the shut-off valve.
3/24/2022 09:01:08 am
I always flow the hydrants closest to the building because that's basically simulating the flow of the fire sprinkler system in the direction of the building if there was ever a fire. If you think you have a abnormal site loop I would recommend conducting 2 or 3 flow tests to make sure your calculation works with the worst case scenario.
3/24/2022 02:22:18 pm
Brian Gerdwagen FPE
3/24/2022 10:24:59 am
The residual hydrant is where your flow and pressure results are valid and where you stop your hydraulic calculations.
3/24/2022 10:31:01 am
I love this topic because it leaves so much room for interpretation (due to actual placement of hydrants, elevations, etc.) and is something that so many AHJs, designers, engineers, etc. have questions on. James is correct, and you do want your static to be as close as possible to your connection point. I will add on a gridded city system, I believe you can place your test point (adjusted for elevation) at the system connection to the city main. Been awhile since I've read 291.
3/24/2022 02:15:14 pm
I typically flow water past the project, and take residual from the hydrant closest to the project.
3/24/2022 02:44:24 pm
As a double check, since you need to flush your underground supply, I would gauge the hydrant closest to the property, put a test header on the F&S, after flushing. Roll out the hoses, pitot, and I don’t believe you can get base of riser flow and pressure more accurate than that. Opinion. Number of hoses depends on calculated demand.
Leave a Reply.
Subscribe and learn something new each day:
Top Feb 2023 Contributors
Get 100 Days of Free Sample Questions right to you!
PE PREP SERIES