A flow alarm in our fire sprinkler system (Background Report)

OUR FIRE SPRINKLER SYSTEM includes an alarm to alert us in the event of unexpected water release. Normally we would not know that it even existed, let alone that it is always looking out for us. I still don’t know where exactly is located. Its measuring probe is just above the hatch in the ceiling of the fire sprinkler room (downstairs). 

The water flow sensor in our sprinkler system

Presumably the associated alarm is nearby—i.e., not far from the doorbell that is above the door to that same room.

The basic operation of such a flow detector is helpfully described on a vendor’s blog, which explains:

“[Such an alarm] signifies an activated fire sprinkler head or a leak in the system.”

The Fire Department requires that this alarm be inspected and tested every 5 years, as part of a regular overall check of our sprinkler system. Our most recent “Fire Protection Equipment Performance Report” (8/16/21) indeed noted that our water flow alarm device consists of a water-flow switch of the vane/paddle type, and that it produces a local alarm sound (as opposed to activating the building’s fire alarm, or being monitored by a supervising station). 

Our switch is meant to activate its alarm if a water flow of 4–10 gallons/minute continues to occur for 20 to 60 seconds anywhere within the downstream dedicated sprinkler lines. 

Nameplate on the water flow sensor

During the next test, which is slated to be conducted later this year, it would be prudent to find out where the alarm is housed and what it sounds like, so as to record both facts for future reference.

A new guess as to why a sprinkler head suddenly failed last June

LAST JUNE, a sprinkler head in the kitchen downstairs suddenly broke open, flooding the area with water — even though no significant heat was present in the vicinity, let alone an actual fire — as reported in this post. At the time, I speculated that the head had deteriorated over time, until it just failed catastrophically.

Since then, I and others (especially the insurance company, so I hear) have struggled to explain why that particular sprinkler head would have been the one to burst. Below the jump, I discuss a factor that recently occurred to me, which I don’t think has previously been considered.…

“Tied-truss” sanctuary roof structure (revised from 8/12/23 version)

ROOF DESIGN is an abiding topic of interest to firefighters, because they need to quickly evaluate the stability of burning buildings. Thus it is not surprising that John W. Mittendorf, a retired battalion chief and training commander for the Los Angeles Fire Dept., discussed various types of roof construction in 2004 on the website Fire Engineering. His articles focused on “older truss roofs” — those that were common in large buildings constructed from the 1800s until the 1950s.

Chief Mittendorf, circa 1993

Below the jump, this post discusses what I learned about Mishkon’s sanctuary roof from Chief Mittendorf’s articles.

A fluke and a flood downstairs

RUBEN TELLS ME that yesterday, he and a plumber were in the process of restoring gas service to the sanctuary building. (Why the gas had been off for a month is a story for another time.) They were in the downstairs kitchen’s closet, bleeding air from the gas line to the water heater. Suddenly, they heard a loud pop and a whoosh. 

Sprinkler shutoff valve
(As usual, click/tap on an image to enlarge it.)

This post describes what happened next, and its import.…