While its nomenclature has varied over the years in NFPA 25 (Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems), the intent of an internal pipe assessment remains the same. The charging section of Chapter 14 highlights the overall purpose of this requirement:

“14.1 General. This chapter shall provide the minimum requirements for conducting investigations of fire protection system piping for possible sources of materials that could cause pipe blockage.”

Chapter 14 of NFPA 25 is organized into four sections: 14.1 General, 14.2 Assessment of Internal Condition of Pipe, 14.3 Obstruction Investigation and Prevention, and 14.4. Ice Obstruction. Section 14.3 is only triggered when there is some indicator that the system may be, or may become, compromised internally. Section 14.4 only applies to dry pipe and preaction systems that pass through freezers or cold storage rooms. 

And Section 14.2 applies to all system types and occurs periodically as a method of inspecting the health of the internal piping of a system. 

It was determined by the National Fire Protection Association membership that there is significant value to periodic inspection of piping due to what is found when we open up sprinkler systems. Corrosion, rocks and all sorts of debris have been found during these internal inspections of fire sprinkler systems; there is concern that if this material is not found and properly removed, a sprinkler or piping system will become clogged. 

Internal Assessment Methods

Annex language in A.14.2.1 of NFPA 25 (2014) provides the intent of an internal assessment for water-based systems, which is to “provide a reasonable assurance that corrosion and obstruction issues within fire protection systems are identified.” While the standard body does not include the procedures for performing this internal assessment, the annex sheds some light on the recommended methods. 

The most common method is to drain and flush the system by opening flushing connections at the end of a main and removing the end fitting or pieces of a branch line to inspect the system visually. The benefits of this method: it is simple to perform and you can see firsthand how the inside of the pipe looks. 

One drawback is that it is invasive; you must drain the system, which requires the impairment procedure of Chapter 15 to come into effect. Also, these sections are only localized representations of a system and do not comprehensively look at the system. 

While we are not required to examine every section of pipe to achieve a reasonable assurance that corrosion and obstruction issues are identified, the inspector should remove several pieces of pipe. Those sections of pipe should be where you would expect to find an obstruction. Corrosion is fairly easy to predict where it will be; it will almost always occur at the water-air interfaces within the system. 

For a wet pipe system, sections of pipe at the high point of branch lines and mains should be removed where air pockets can be trapped. For dry pipe systems, low points on branch lines and mains should be removed where water can collect and not drain completely — essentially, any place where there will be trapped air or trapped water is where corrosion will commonly exist. When performing an internal assessment, collect samples of any foreign material found and take photographs of the internal pipe condition for records. 

Alternate methods also are mentioned in the annex under A.14.2.1, which lists acceptable options: video inspection equipment, ultrasonic imaging and laboratory analysis of water samples. The most thorough of these is likely the video inspection equipment, which generally consists of a camera on a snake being fed down the mains and branch lines. This is similar to draining and visual inspection of pipe sections; however, it provides a complete picture of the system’s inside as the snaked camera is fed through more of the system. 

The newer technology is ultrasonic imaging, a noninvasive procedure to determine the wall thickness of the pipe through wave propagation. It requires the ultrasonic imaging device to be placed against each section of pipe. One benefit is that you are not required to drain or enter the system’s piping. Another benefit is that it can cover entire or multiple systems relatively quickly. 

However, the drawback here is ultrasonic imaging may not pick up on obstructions or hyper-localized microbial-induced corrosion (MIC), corrosion that occurs due to microorganisms in the sprinkler system and generally causes hyper-localized pitting in steel pipe. 

The final method is water sampling. This method is also noninvasive and can identify corrosion, MIC and other foreign materials by bringing a water sample from the pipe to a laboratory for testing. Regardless of the method, if corrosion or an obstruction is found, an obstruction investigation is likely to be triggered.

Obstruction Investigations

An obstruction investigation is more involved and serves a different purpose than the periodic five-year internal pipe assessment. The investigation is triggered when one of 15 conditions occur, which could indicate that the system may be or may become compromised due to some physical obstruction:

1. Defective intake of fire pumps taking suction from open bodies of water.

2. Discharge of obtrusive material during routine water tests.

3. Foreign materials in fire pumps, in dry pipe valves or in check valves.

4. Foreign material in water during drain tests or plugging of inspector’s test connection(s).

5. Unknown materials are heard in the system piping during draining, refilling or otherwise flowing water through the system.

6. Plugged sprinklers.

7. The presence of sufficient foreign organic or inorganic material found in the pipe.

8. Failure to flush yard piping or surrounding public mains following new installations or repairs.

9. A record of broken public mains in the vicinity.

10. Abnormally frequent tripping of dry pipe valve(s).

11. A system returned to service after an extended shutdown (greater than one year).

12. There is reason to believe the sprinkler system contains sodium silicate or highly corrosive fluxes in copper systems.

13. A system has been supplied with raw water via the fire department connection.

14. Pinhole leaks.

15. A 50% increase in the time it takes water to travel from the inspector’s test connection to when the valve trips during a full-flow trip test of a dry pipe sprinkler system, compared to the original acceptance test.

Whenever any of these 15 conditions are observed, a full obstruction investigation is required to be performed. Therefore, an obstruction investigation would be required if one of these 15 conditions is observed during an internal pipe assessment. 

One thing an internal assessment will address that an obstruction investigation does not is the creeping effect of corrosion over time. An obstruction investigation will only be triggered when corrosion is significant enough to cause one of the 15 aforementioned conditions. 

Periodic internal assessments allow the owners to locate and handle corrosion issues before they affect the system’s performance. This concept is exemplified by the exception of nonmetallic pipe in NFPA 25, which is not required to have internal pipe assessments since they do not corrode as metallic pipes do. 

Draining a system can be a timely and costly event for a building. This five-year interval for the internal assessment was decided on to correspond with other requirements in NFPA 25. Both alarm valves and check valves are required to be internally inspected at a five-year interval; therefore, all inspections should be coordinated to occur at the same time. 

This allows building owners to only drain a system once for both the internal pipe assessment and the interior check valve inspections. Performing all internal inspections at the same time reduces the overall downtime of the system and will leave more money in the owner’s pocket. 

Another technique to reduce the downtime and cost of these inspections is to perform them any time the system is drained, regardless of the time elapsed since the last inspection. If a system must be drained for a renovation, repair or some other maintenance reason, schedule the internal assessment and internal valve inspections at the same time. This resets the clock and provides another five years before another internal assessment is required.

Sprinkler System Definition Change

A change occurred in the 2013 edition of NFPA 13 to the definition of a sprinkler system, which affects the internal assessment of water piping systems. The definition of a sprinkler system now includes “a water supply source, a water control valve, a waterflow alarm, and a drain and is commonly activated by heat from a fire, discharging water over the fire area.” 

Based on this new definition, all floor control valve assemblies in multistory buildings would represent a different sprinkler system. High-rise buildings would typically have at least as many systems as it does floors. It was permitted to have an internal pipe assessment on every other system on a five-year interval to handle high-rise buildings and large facilities with multiple systems. 

For example, if you had a 20-story building with 20 systems, you could inspect all 20 systems every five years. Or, based on this allowance of an internal assessment on every other system, you could inspect 10 systems one year, then inspect the other 10 systems five years later, returning to inspect the first 10 systems five years after that. This essentially allows every other system to be inspected on a 10-year interval, even though they are fed by the same water supply and would generally be subject to the same levels of corrosion. 

This allows owners to stabilize costs over time rather than draining all systems and paying for the inspection on all 20 systems. However, if any of the 15 aforementioned obstruction investigation triggers are observed, then a complete obstruction investigation would be performed on all systems in that building. 

Following the inspection, testing and maintenance procedures in NFPA 25 are essential to sustaining a properly functioning fire sprinkler system. Through experience and research, the technical committees have identified important periodic inspections and tests to ensure fire sprinkler systems activate effectively during a fire
situation. 

While the internal assessment of pipe is one of the more cumbersome inspections, the benefits outweigh the costs when done thoroughly and with the other five-year internal inspections of check valves and alarm valves.

Louis Guerrazzi, EIT, is the director of course and content development at the Society of Fire Protection Engineers. Contact him at lguerrazzi@sfpe.org.