my experience is that the "loop" has no Isolation valves on it ... the downstream or lead-in supply piping to the various structures fed off of the loop would have isolation valves prior to the supply piping entering each structure .. which of course must be locked out (locked in open position) or monitored by the fire alarm system
As a contractor, depending on loop size, I would advise installing isolation valves. This will help while installing, as you can pressure test against that valve and then bury that area once it is approved. If you try and test the entire loop and have a leak, good luck searching the entire loop. Unfortunately, I've seen other contractors do this and it's an expensive nightmare. I'm sure there is a code for this also. But where I'm from, plumbers have to do a majority of the UG now.
May not be required at the pump discharge to the loop per NFPA 24. But it would be a good location for valves for isolation purposes depending on how many hydrants and other connections provided.
Common recommended practice to have isolation valves on a loop system.
And having valves on the tee just outside the pump room is a good start (that way, you can isolate one way (say left) and feed the rest of the loop from the other way (say right) up to the area where you isolate a second valve for repairs on a section of your underground system.
I don't remeber if this is an NFPA requirement or FM Global requirement, but again, a common recommended practice to have no more than 5 systems isolated in case of impairment n an underground main (5 systems may be 5 sprinkler control valves, 5 hydrants or any combination of those).
We do this on large steam utility system as well when they are looped and cross-fed. Typically at the up and down stream piping entrances in the building service manhole and on the take off in a manhole. Sometimes you'll see up and down stream of each take off as well. I've also seen separate isolation manholes up and down stream of the building service manhole; that gets expensive.
One of my common recommendation is the following:
Approved visually indicating sectional control valves should be provided to isolate portions of the fire main loop for maintenance or repair without having to shut off large portions of the water supply to fire suppression systems.
Underground loop isolation valves shall be located not to exeed six(6) users of fire protection connection between the valves according to NFPA 24.
6.6 Sectional Valves.
6.6.1* Sectional valves shall be provided at appropriate loca‐
tions within piping sections such that the number of fire
protection connections between sectional valves does not
Thank you for all the input everyone!
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