To Replace or Not to Replace – System Gauges

NFPA 25, The Standard for Inspection, Testing, and Maintenance of Water-Based Fire Sprinkler Systems is the minimum standard for building owners to properly maintain their buildings’ fire sprinkler systems. The requirement for inspection and testing of system gauges can be found in Chapter 13 of the 2020 edition.  Section 13.2.5 provides the inspection requirements, stating that water pressure gauges are inspected quarterly, and if constantly monitored, air or nitrogen gauges are also inspected quarterly. If not monitored, then these gauges must be inspected monthly.  There are some other inspection requirements that can be found in this section for specific situations.

Section states that gauges must be replaced or tested every five years, and Section says that if the gauge is not within 3% that it must be recalibrated or replaced. This is where we get into the meat and potatoes of what the standard requires.


fire sprinkler system gauge


Most of the time, contractors will simply replace the gauge every five years, there is nothing wrong with replacing it, and it certainly meets the requirement of the standard.  However, the reason for replacing the gauges is that the requirements for comparing them is somewhat misunderstood.  Many say that replacing the gauge is easier than calibrating.  Yes, I said calibrate, but that is not what is required.

WORDS MATTER!!  Nowhere in NFPA 25 does it say that these gauges must be calibrated.  The standard simply says these gauges must be compared to a calibrated gauge.  This is important because calibrating a gauge is much more involved and can be costly, as stated in my blog from June 2020 about gauge calibration.

To meet the requirements of NFPA 25, the system gauge(s) must be compared to a calibrated gauge.  This simply means to compare the existing system gauge pressure to the calibrated gauge pressure and the reading must be with in ± 3% of the full scale.  Typically, we use 300 lb. Gauges, which means that the compared reading must be within ± 9 PSI. That is a large allowance.  If the gauge was a 200 lb. gauge the allowance would be ± 6 PSI.   In many cases, these gauges would pass if compared to a calibrated gauge.

The question is, is replacing the gauges easier than calibrating? That depends on how the gauge is installed.  If on a three-way valve, simply close the valve, remove the plug, install the calibrated gauge, and reopen the valve.

Voila, the task is done.  If the gauge is installed so that the only way to compare or replace the gauge is to drain the system, then do so and install a three-way valve for the next required five- year test.

If there is a manifold with several systems, the test gets even easier.  A calibrated gauge can be installed in one location and all gauges on that manifold could be compared to the calibrated gauge at the same time, meaning that not every gauge has to be removed and/or compared at each alarm valve.

In the image below I would only have to install a single calibrated gauge to compare every gauge installed on every system on this manifold.

fire sprinkler system with gauges

In the end, it boils down to ease of comparing or replacing, and customer service.  Sure, there is money to be made from replacing gauges, but in a building that may have a large quantity of gauges it is a cost savings for the owner to compare gauges rather than replace them.

I have won several inspection and testing contracts by suggesting comparison over replacement.  Remember that NFPA 25 is the minimum requirement, and that as a contractor you are there to provide a service for your customer.


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