Establishing the current corrosion condition in an existing sprinkler system is critical in controlling maintenance costs for the end-user in the immediate and long terms.
With today’s steel pipe market volatility, unprecedented price increases for steel, and limited inventories available to contractors, preserving existing piping and catching problems in advance is more critical than ever to control building maintenance costs.
How to Address Repair & Remediation Costs
Proper investigation methods and analytic resources provide more options for rehabilitating problem systems without undergoing complete system replacement.
These methods and resources also allow inspectors to make proactive recommendations on annual and five-year inspections to give the customer time to budget for repairs before problems happen that result in property damage.
How to Establish the Current Condition of Corrosion
To establish the current corrosion condition, start by qualifying the age of the building, type of system (dry or wet), and the pipe wall thickness.
Systems constructed in the early 1990s-2005 (15-25+ years of age) are prime candidates for pipe failure. During this period, the sprinkler industry started using lightweight piping for hydraulic benefits and project cost control. These systems are commonly at the end of the life cycle for lightweight schedule, 5, 7, and 10 systems.
Insider tip: A very high percentage of calls ECS receives from contractors or building owners for pipe failure problems tend that fall right in this building age range.
These buildings all have large volume wet systems with frequent draining activity or dry pipe systems with a lot of trapped water kept pressurized by an air compressor.
Look at the Building Type
The buildings subjected to the worst corrosion damage are large volume wet systems with frequent complete drain down activity. These facilities are most often warehouses, logistics, bio labs, stadiums, shopping malls, parking garages, and multi-story facilities. Reasons for full drain down might include tenant improvement work through the course of a year.
Dry or preaction systems also have challenges when it comes to corrosion damage. Dry pipe and preaction systems with poor drainage or that are not pitched well cause trapped water, contributing to corrosion damage. They will have the highest obstruction risk out of any type of sprinkler system.
Dry pipe and preaction systems fail 3-4 times faster than wet systems due to the constant air supply induced by air compressors which rapidly results in severe corrosion damage in locations where trapped water is present. The pipe in these systems can fail in less than ten years, depending on how much trapped water exists inside the system. Furthermore, if the pipe is galvanized, it is prone to aggressive pipe failure.
If any buildings you own or are currently inspecting meet the criteria above, it is time to start recommending pipe sample analysis on inspections.
Perform a Pipe Sample Analysis to Determine Corrosion Extent
Your next step before determining whether to repair or replace should be to perform a pipe sample analysis.
How Pipe Sampling Works
The contractor should cut a 1’-0” section of pipe from the system in locations prone to failure.
The sample is cut in half and media blasted down to determine the type of corrosion, and most importantly, to quantify the amount of metal loss.
Dry / Preaction Systems
Samples are taken from areas that do not drain or where water is trapped with non-flowing standing water on metal with air above it.
Wet Pipe Systems
Samples are taken from high branch lines, mains, top of the standpipes, or anywhere where air is most likely to be trapped and is the location where pipe failure occurs. Packed water sections without any open air do not have corrosion damage.
Fire Supply Loops
Pipe sampling should also be done closest to the flowing media or fire pump. Taking samples starting near the pump and space them out every 100’. The farther away you get from the pump, you’ll see the wear on the metal begins to reduce based on the analysis of multiple pipe samples. This will give you an idea of what sections of the supply loop you need to keep an eye on or sectionally replace vs. replacing ALL the supply loop.
All Systems: Get a Comparative Sample
It is also good to take samples from locations on the system where you know corrosion is unlikely to show to serve as a contrast between the known failure points. These are water-packed locations (no air pocket) in wet systems and dry systems with no trapped water.
These samples reassure the client/building owner that systems with chronic leaks don’t mean all of the pipes are bad, and there are cost-effective ways to rehab the system and leave the good pipe in place.
Use Your Corrosion Report to Make a Decision with the Building Owner
When you get the completed samples back to ECS, you’ll receive a report within two weeks, and we will return the sampled pipe to review with your customers. The building owner will see firsthand what the scarring or wear looks like where the water was sitting inside the pipe.
The report with the sample will include:
- Wall loss %
- Likelihood of a leak based on the sample
- Areas of the system that need attention
- Mitigation options
Recommendations for Wet Pipe and Dry Pipe Systems: 15-25+ Years of age, Schedule 5, 7, & 10 Pipe
- Annual or 5-year Inspection: Write up a pipe sample as a “Comment or Recommendation” to determine wall loss and assess internal pipe integrity, even if the systems are not leaking yet. Once the wall loss has been determined, areas with wall loss measuring in the 70%-90% percentile, the client is very close to a leak.
- Generate a Repair Quote: Write up a repair quote to have the pipe repaired or replaced in the area where the contractor took the sample. If these are areas where scaffolding is needed or in a location that is hard to get to, the cost of that repair will get someone’s attention. Property loss damages and business interruption from a pipe failure event in a mission-critical facility can have significant consequences. You’ll do right by your customer by letting them know about the problems well in advance and allowing them to respond and time to prepare budgets for pipe replacement and mitigation options.
- Video Scope Analysis: Should pipe replacement be requested as an option, perform a video scope analysis to get a real-time view inside the system. The contractor will scope the pipe in areas where corrosion is most likely to occur. Based on this, you can provide a surgical pipe replacement option for the bad pipe but leave the good pipe in place. The previous pipe sample already provides the data to support what you’re recommending. When the pipe is remediated, it reduces overall replacement costs by 80-90%.
- Retrofit Work: For General Contractors that are performing building renovations and retrofit work, keep in mind that a surgical pipe replacement option will also reduce the overall work scope of the whole project with other trades, not just the fire protection. Since a smaller portion of the building has to be demoed out to access existing pipe, this results in significant cost reduction for the owner.
- Wet System Venting: Placing automatic vents on wet systems is the least expensive method of oxygen control during each drain & fill on existing systems and new systems to control corrosion by 50-60%. Manual vents (i.e., ball valves) are worthless as they require human intervention to operate during service work, and a lot of times are hard to find in an existing building if you’re a service provider. Once they are installed new and past a one-year warranty period, nobody will likely use the manual vent ever again. Automatic vents are the only way to go if the client/contractor is serious about oxygen control in these systems and to ensure the device performs its intended function.
- Wet System Nitrogen: Nitrogen is used to deoxygenate the trapped gas content inside the sprinkler system before water gets put back into the pipe after a repair or tenant improvement project. This maintains an oxygen-free sprinkler system (verified by a gas analyzer), which will not corrode. When this is performed before filling the system back up, this preserves the metal internally and will stop leaks and scaling debris. Ideal for systems with chronic leaks or an alternative to pipe replacement.
- Wet Systems: It is also ideal to install a remote auxiliary drain to be utilized as the gas release location if using nitrogen. Inert gas can be released and tested for oxygen content at this location, and keeps the process on the ground and easy to access.
- Dry Pipe / Preaction: If the air compressor keeps running, there is a good chance you have pinhole leaks developing in the system. We recommend converting to a Nitrogen Generator that will maintain an oxygen-free pneumatically controlled system and meet the 30 minute fill time required by NFPA 13. The generator will have the same outcome as taking all the oxygen out of the pipe in a wet pipe system. Water is noncorrosive to the metal in an oxygen-free closed system, whether it’s atmospheric 98% nitrogen in wet or pressurized 98% nitrogen in a dry or preaction—it is the same result.
- Dry or Wet Systems: Sprinkler systems should always have the ability to drain out as much as possible if your customer ever wants to treat their corrosion problem. Add low point drains as necessary in either type of sprinkler system to better control corrosion in dry systems that are not well-pitched. It can be challenging for nitrogen inerting wet systems to get nitrogen gas into the remote areas of system piping if areas are blocked by trapped water. Adequate draining is essential for all levels of corrosion control using nitrogen gas!
Proper testing and analytics go a long way toward corrosion and preventive maintenance, and budget planning. The problems we hear about every day in our industry are avoidable and don’t have to lead to unplanned repair costs and situations where full system replacements are the status quo. We can catch these problems before they happen.