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Does anybody have a reliable and accurate formula to figure out the flow through the 3" gang drain for a high rise standpipe with PRVs?
This to size the floor drain properly and to pass along to the plumber. Also, when draining a system, you only drain one system per floor at a time when needed. The annual testing of PRVs, would be the worst case scenario in my opinion...250 gpm out of each. The 500 gpm at the roof should be handled by the Rain storm drains, right? Thank you kindly. Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
3 Comments
Mike
2/6/2020 10:55:41 am
Drains are required to accept maximum system flow.
Pete D
2/8/2020 08:13:57 am
On combined systems, and I don't know if that is your case, the standpipe drain serves as the inspectors test drain as well as to drain the system. With that in mind and echoing Mike, expect the drain to receive the full flow of the overhead system. For office that would typically be 250gpm + any overflow. You can use 500 gpm to be safe. I'm assuming by "gang drain" you want to size an emergency open floor drain. The standpipe drain should be run out of the building. If the drain is going to be a closed drain below ground and it is a combined system, the plumber has to consider that for PRVs at the hose connections, overhead systems have a different maximum pressure than class 1 standpipes. Assuming 175 psi at the control arm assembly, the drain will pickup all the gravitational potential and flow until it reaches energy equillibrium with the supply. You can run a source calc, or a safe number to use for design, neglecting loss, is the static pressure at the top floor plus the product of the difference in elevation to the drain and the pressure gradient. This may exceed 300psi.
Mike
2/9/2020 02:06:49 pm
It is also used to test and set the pressure settings of the Pressure regulating valves should they be installed. Leave a Reply. |
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