Following photo is of a FDC check valve by-pass (located somewhere in the mid-east, I'm not permitted to say where). You wouldn't know this was a check valve FDC by-pass without looking at the system. Missing signage, missing tamper (e.g. chain lock). These are nice when you have to flush the FDC. In some markets they are mandatory (e.g. Boulder, CO).
Leaking check valves. In attics. Not subject to NFPA 25 inspection.
Photo below shows system as found - apparent un-repaired leak on check valve drain. Image redacted.
In other matters. A customer was experiencing high system side pressures and corresponding leaks on an anti-freeze based gravity fed fire sprinkler system. The client's structure consisted of protected combustible ordinary construction, the attic was also protected. No backflow preventer was installed due to the isolated gravity (water tank) fed system, however, a 4" check valve was installed, a pressure relief tank was not installed. The check valve was removed to inspect for the required 1/32" pressure relief "hole". None was found. System side pressure was being thermally loaded by solar radiation and building heat, no where for the pressure to go. Design/install error.
Here's another failure (see below):
And another failure. The failure below is on the southern most continent. The system feed is via A 175 psi air charged 7500 gallon water pressure tank. Drain plug had failed due to corrosion.
Interior of a different 4" check valve (on a FDC) is shown:
Leaking check valves. In attics. Not subject to NFPA 25 inspection.
Following series of photos show an internal check valve inspection. This is on a gravity tank supplied PG anti-freeze system. Sprinkler contractor logo has been redacted.
Photo below shows system as found - apparent un-repaired leak on check valve drain. Image redacted.
Next series of photos show a leaking FDC connection on a newly installed 13R system. Investigation later showed that the FDC check valve (not pictured) was installed backwards. The system had to be impairment tagged due to the excessive water pressure that would have resulted had the fire department (or others) unknowingly removed the FDC plug. Design/Install error.
And another failure. The failure below is on the southern most continent. The system feed is via A 175 psi air charged 7500 gallon water pressure tank. Drain plug had failed due to corrosion.
Interior of a different 4" check valve (on a FDC) is shown:
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