Photo Gallery F4:  Wet Fire Sprinkler Wet fire sprinkler systems have long been trouble free, until more recently that is.  Filling steel pipe with water and leaving it stagnant, which is how wet fire sprinkler systems existed many decades ago, results in limited corrosion occurring before the oxygen is expended and corrosion dramatically slows.  This is why UT investigations at much older buildings often produce the best results.  Refresh it with new water on a regular basis and the corrosion mechanism returns to its higher rate. Today, however, mandated regular flow testing combined with the more common installation of thinwall schedule 10 pipe and even ultra thinwall schedule 7 have greatly accelerated their deterioration.  Long gone is the standard for schedule 40 pipe.  Highest wall loss always exists where fresh water flow is higher – such as prior to a leaking booster pump seal.  Sweating pipe, as well as a frequently running jockey pump, always indicates a downstream leak requiring immediate attention.  Frequent building renovations requiring draining and re-filling are extremely damaging to the entire system, whereas a leaking booster pump seal may only impact 25 ft. of inlet line.  Where short distances exist between the inlet fire line to…

Photo Gallery F3:  Dual Temperature Dual temperature piping systems are under an equal threat to chill water systems, with the main differences being the size of the pipe, their location, and an extensive layout within the building property.  They utilize one set of risers to supply both cold and hot water depending upon seasonal requirements.  Dual temperature systems are the primary means of heating and cooling for apartment and condominium complexes, with less presence at high rise office buildings. As closed systems, they should have low corrosion activity at under 0.5 MPY.  However, over decades and especially when not adequately maintained, significant rust product can be produced, and will often reveal itself in the form of reduced heat transfer.  Turning down chill water temperatures and hot water temperatures up to offset such heat transfer loss solves nothing other than to increase condensation and external corrosion activity during summer months. With the risers typically installed at the perimeter columns, they are highly impacted by moist air infiltrating through the building envelope.  Most such systems were poorly insulated, with 1/2 in. insulation installed, the insulation missing or incomplete.  The fact that such pipe was never expected to see the light of day…

Photo Gallery F2:  Chill Water Chill water systems, also termed chilled water, are fundamental to virtually all larger building properties.  Unlike condenser water service, they benefit from far lower internal corrosion activity but then have a potential secondary corrosion front occurring externally.  The smaller lines to any chill water system are the most vulnerable due to lesser wall thickness, threaded construction, thinner insulation, and their frequent placement in areas of higher humidity – such as within fresh air plenums, mechanical rooms, and at perimeter building columns. A common issue called CUI, for corrosion under insulation, applies to the failure of the insulation to protect the pipe exterior.  This is less a failure of the insulation itself and more of a design, installation, and maintenance issue.  Nevertheless, CUI can easily destroy a chill or cold water piping system far in advance of just internal corrosion alone, and is a significant problem for both 2 pipe and 4 pipe HVAC systems.  Whereas internal corrosion activity can be controlled to near 0.5 MPY with little effort, an aggressive external corrosion condition can multiply that loss 5 times or more.  And unlike the application of chemical water treatment, there are no preventative methods available…

Photo Gallery F1:  Condenser Water Evaporative condenser water systems are common to any larger building property and are critically important to air conditioning needs.  Various forms of system exist including those that serve large central refrigeration plants, smaller individual package units on each floor, and at various types of heat pump systems. Corrosion activity is typically higher for condenser water pipe due to many different factors, and depending upon piping design, can cause serious failures and operational difficulties within just a few years.  Of the many different piping systems common to any building property, condenser water systems typically require the highest maintenance and cost outlay – yet still present the highest level of problems.  Operating under reduced chemical protection levels, saturated oxygen levels, constant microbiological attack, and with the cooling tower itself basically a giant air scrubbing device constantly introducing dirt and particulates into the system, corrosion levels are now considered normal by some authorities if maintained below 5 MPY – a dramatic increase from the 1 MPY level commonly maintained 30 years ago.  The declining quality and increased corrosion susceptibility of new steel pipe only adds to the corrosion rate equation. Virtually all condenser water systems are constructed of…

Photo Gallery B7:  Erosion Corrosion Water flow induced erosion is primarily a mechanical force based deterioration although chemistry usually plays some role.  It is heavily dependent upon water velocity and the “softness” of the piping material, with secondary factors such as water chemistry, piping layout, and particulate content also involved.  While a potential threat to most HVAC and plumbing piping systems, it is far more common for copper pipe providing domestic water service. While multiple causes exist, copper pipe erosion is primarily related to higher than normal water velocity which then produces cavitation immediately downstream of elbows, tees,valves, and other fixtures.  Even the smallest interruption to laminar flow, such as the failure to bevel or camfer the pipe ID can lead to cavitation – an issue we have been raising for various forms of pressed copper pipe assembly alternatives to soldering. Its impact is amplified by heat, which is why a higher level of deterioration is commonly found at the hot water lines, and those closest to the boiler.  Softened water, and especially RO water, also play a significant role since they remove key chemical elements which actually protect the copper.  The demand for more control…

The issue of supporting a tank or pressure vessel is generally not an issue except where the tank is in an outdoor environment, or where it is subject to colder temperatures.  For large and tall domestic cold water tanks. the older inlet water will sink to the bottom where it stratifies in temperature gradients.  The coldest water at the bottom then condenses area moisture that migrates between the base of the tank and supports. The strength of expanding rust is so great that we have documented it to have raised a 35,000 gallon steel house tank 3/4 in. above its I beam supports, placing noticeable stress against every piping connection.  In addition, the bottom to most larger rectangular water storage tanks is rarely painted – leaving this hidden space far more vulnerable to corrosion.

Photo Gallery E4:  Fire Water Storage Fire water reserve storage is common to most larger high rise properties.  Many are in the form of large round pressurized vessels while others are square and rectangular gravity tanks.  Smallest properties may be served sufficiently by city pressure, with many increasing that pressure and flow through fire booster pumps. For many large domestic water storage tanks, the lower portion of the entire tank is typically reserved for fire protection only; the domestic water lines taking-off from a higher level.  When shared with domestic water service, oxygen levels are substantially higher due to the constant introduction of fresh water – thereby driving a higher level of corrosion activity to the entire tank and all associated piping.  Conversely, where the tanks are dedicated for fire service only and have a minimal exchange of water, oxygen levels are lower and far less corrosion should exist. Pressurized fire reserve tanks are commonly installed in order to provide adequate water pressure to a building’s top floors where gravity flow is insufficient.  With their make-up and outlet typically at the front, water entering the tank short circuits without circulating throughout the entire tank, and therefore corrosion activity is often…

Photo Gallery E3:  Domestic Water Storage The generally deteriorated condition of most domestic or potable water steel storage tanks is shocking given the public awareness to pollutants in the water supply.  Although so few tenants drink water from a sink or fountain that the water fountains for many commercial office buildings have been removed, everyone comes in contact with water carried through some form of storage container on a daily basis.  For tenants of high rise apartments and condominiums, contact with the water stored in cold and hot water tanks is far greater. For older tanks dating back before the 1950s, red lead paint and coal tar was the common protective agent guarding against corrosion, as well as other even more carcinogenic agents.  Many such tanks still remain in service, and will not be exposed for the threat they present until a leak occurs.  It is then up to an observant investigator to point out a concern no one really wants to address. Almost all domestic water storage tanks carry a fire water storage reserve, which leaves the bottom 3-5 ft. of the tank remaining relatively stagnant.  Inside ladders often suffer the most advanced corrosion, with some resembling those still…

Photo Gallery E2:  External Tank Corrosion Similar to our comments regarding external corrosion and weathering at steel pipe, external corrosion to any tank is simply due to a lack of maintenance.  External corrosion is a far greater problem for cold water storage tanks over most other types.  Large 25,000 gallon domestic water storage tanks are typically not insulated.  With only a small turnover of water entering and leaving, colder inlet water sinks and often stratifies toward the bottom of the tank where it produces a colder tank surface favoring moisture condensation.  Colder temperatures in turn corrode the vertical I beam supports if external, and most importantly, the area of contact between the horizontal I beam supports and tank bottom.  For square and rectangular tanks, the bottom is rarely painted – thereby creating another surface vulnerable to corrosion attack. For cold water storage tanks, it is important to remember that rust increases in volume and can impart a tremendous physical force as it increases.  Rust between the tank bottom and supporting I beams can actually raise up a 40,000 gallon house tank an inch or more; producing new stresses upon all inlet and outlet piping. Outdoor located tanks are obviously at…

Photo Gallery E1:  Tank Leaks And Repairs Most tanks are fabricated from sheets of flat or rolled mild carbon steel, and are subject to various forms of corrosion.  Generally, an internal coating is applied to isolate the underlying steel, although like most forms of protection, failure of the coating at some future date will occur.  Since the predictive assessment of tanks is rarely performed, the first indication of a problem is typically when a leak or failure occurs.  For domestic water storage tanks, the annual requirement to physically clean and sterilize the interior should provide a regular opportunity to also inspect for other physical deficiencies, although this minor action is quite often overlooked Leaks at the pipe to or from a water storage tank also provides a good indication to a potential problem, given that the same level of corrosion activity will impact all such metal surfaces.  A failure at either the tank or pipe serving to or from the tank provides an indication to the deterioration of the other component as well.  Generally, the type of failure and its location is greatly dependent upon the type of tank or pressure vessel involved.  Dedicated fire sprinkler water storage tanks, since…