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 A Hidden Time Bomb - Corrosion of Piping Systems
Causes of Corrosion in a Piping System, Traditional Repair Methods 

and the Modern System of Pipe Restoration 
January 2000 - Recently in British Columbia the issue of leaky condo�s has caught the attention of consumers, engineers, realtors, builders, government agencies. Initially and perhaps still, the issue created a valuation challenge for those involved in the appraisal profession. 

Ready for a new challenge, what about the next big �Leak� issue. Only this time it is international in scope and involves the building�s piping system, leaking from the effects of corrosion. 

Out of sight and out of mind, hidden behind walls and in ceiling cavities, water pipes have been deteriorating with few paying any attention to scope of the problem and the potential cost to cure. 

For those involved in the appraisal profession it may be time to take a look behind those walls, so to speak, and understand just what is happening to those water lines. Consider the effects on building valuation and how repairs can be made to mitigate direct damage and loss of revenue. 

In this article we will look at the causes of corrosion in a piping system, traditional repair methods and how a modern system of pipe restoration, not only repairs the piping system while it is in the walls of the building but stops the corrosion process from coming back. With pipe restoration, no walls need to be torn out, no tile to be removed, no mess, loss of room revenue is kept to a minimum and typically a piping system can be restored in ½ the time with savings in the 30% to 60% range over the cost of a conventional re-pipe. 


A good starting place is to get familiar with the pH levels in your local water supply. A low pH will indicate the water has an acidic nature which can be corrosive to a piping system. 

When on site, your inspection of the building�s mechanical systems should include a look at the piping system. Note the type of material the piping system is constructed of. If copper, look for green stains in sinks or tubs. In areas where the pipe is visible look for evidence of leaks or repairs including sections of new pipe or the use of gear clamps, which are used as a temporary stop gap measure on pin hole leaks. Look for water stains on ceilings and ask the question to the building manager about his experience with leaks in the piping system. 

If the piping system is constructed of galvanized steel, again look for evidence of repairs or leaks but also check the water pressure as you tour the building. Low water pressure and changing water pressure usually indicates that the pipes are encrusted and the water flow is being restricted. As well as asking the building manager about leaks, repairs and water pressure, ask about water pump replacement. Pumps that work harder to deliver water through heavily encrusted pipes usually wear out faster, another good indicator of encrusted pipes.


In a piping system there are a number of factors working alone or in combination that can effect the rate of corrosion occurring in pipe. Depending on the degree of these factors a new piping system can show signs of corrosive wear in as little as two years after installation. 

The corrosive effect the source water can have on the piping system does not mean poor water quality is being delivered. In fact in the Pacific Northwest region of the United States and Canada, the source water quality has been rated as some of the best drinking water in the world. Yet, that water has a very corrosive effect on piping systems. 

The rate of corrosion on a piping system is related to basically these factors:

  • the pH of the water
  • the amount of oxygen in the water
  • the chemical make up of the water
  • the amount of galvanic corrosion from the use of dissimilar metals contained in or in contact with the piping system
  • the temperature of the water
  • the velocity/pressure of the water in the pipe

Acidity of a water sample is measured on a pH scale. The pH scale ranges from zero (maximum acidity) to 14 (maximum alkalinity); the middle of the scale, 7, represents the neutral point. Acidity increases from neutral toward 0.  The pH scale is based on logarithmic progression like the commonly used �Richter� scale for earthquake measurement. A difference of one pH unit represents a tenfold change in acidity. Normal rain has a pH of 5.6 � slightly acidic because of the carbon dioxide picked up in the earth�s atmosphere by the rain. Acid rain with a pH of 3.6 has 100 times the acidity of normal rain with a pH of 5.6! 

In copper pipe systems when the pH is more than 8, a copper oxide film is usually formed on the pipe walls. This film acts as a barrier that slows the effects of corrosion. However, when the pH in the water supply is lower than 8 in the water supply the copper oxide film (barrier) is dissolved leaving no protective barrier and the pipe is subject to the corrosive action of the water. 


A domestic water system is an �open� system where the water in use is always being replenished with fresh oxygenated water. Dissolved air in water consists of about 30% oxygen and the rest is mostly nitrogen, which is non-corrosive. Oxygen degrades metals through an electro-chemical process of internal oxidation. The result is that metal gradually gets converted to an oxide (rust), becoming thinner and weaker in the process. As the pipe corrodes the impurities are deposited in the water lines. Encrusted build up is the direct result of the oxidation process. 

While oxygen content decreases under higher water temperature and higher pressure it is these higher temperatures and higher pressure conditions that speed up the oxidation process. Experience shows that corrosion is more pronounced in hot water lines. 


Dissolved minerals in the water and the basic chemical composition of the water may have differing effects on the corrosive forces at play. For example a moderate to high level of calcium would help form a protective coating on the pipe which could slow down the corrosive effects. However, high levels of calcium may cause a calcium build up in the pipe. 


Galvanic corrosion, also known as electrolysis, occurs when different metals come into contact with each other. When conflicting metals are touching each other one of the metals has a tendency to give up electrons. Basically at the point of contact the metal giving up the electrons dissolves over time. The most frequent cases of this happening are when galvanized pipe and copper are connected; copper pipes touch steel studs, or steel pipe hangers. Contrary to common belief, the effects of galvanic corrosion are limited to the immediate area of contact. The use of dielectric fittings helps stop the problem but does not repair the resulting thin walled and damaged pipe. 


The higher the water temperature the faster the rate of oxidation. Experience shows that corrosion is more pronounced in hot water lines. 


Water velocity problems are usually associated with a �closed� loop piping system where the need to pump or circulate the water is required. 

Erosion corrosion occurs at locations where water turbulence develops. Turbulence can be caused by excessive velocity, sudden changes in direction (sharp turns, elbows) and through �flow� obstacles such as burrs and solder excess. 

In the case of copper pipe, a copper oxide layer is established under the right pH conditions on the inside surface of the pipe and this acts as a protective barrier. However, when the water velocities are above 4 ft/sec the copper oxide layer is destroyed or cannot form in the first place. Without this oxide layer the metal will tend to deteriorate at a more rapid rate. 

The major contributing factors to this type of erosion corrosion include:

  • water velocities exceed 4 ft/sec
  • oversized circulation pumps
  • installation of undersized distribution lines
  • multiple or abrupt changes in the direction of the pipe
  • burrs on the inside of the pipe
  • improper soldered joints
  • improper balanced system

The internal corrosion of piping systems raises health concerns. These health concerns include the negative health effects associated with the leaching of lead, copper and other harmful metals from water pipes into the drinking water supply. 


There are various traditional methods available to treat the problems of corrosion but in any given case each situation must be explored separately. 

The cause and effect of the corrosion must be identified. Items like water chemistry vary from one geographic region or from one water source to the next. The design of piping systems varies from building to building. Water velocity, water temperature and even the metallurgy of the piping system need to be identified. 

Some of the more traditional methods of repair focus on:

  • chemical flushing of the system
  • spot repairing  and replacement
  • redesign the hot water recirculating system to keep water velocities below 4 ft/sec for temperatures up to 140 oF, for water temperatures over 140oF flow maximums are recommended to not exceed 3 ft/sec
  • avoid abrupt changes in piping direction
  • de-burr all tube ends before joining
  • ensure all proper soldering joints
  • ensure no dissimilar metal are in use or at least they are isolated
  • spot repair using gear clamps or other temporary device
  • use a water treatment system to adjust the water quality and chemistry
  • repipe the building in whole or in part
  • install some form of system to stop galvanic corrosion from occurring
In almost every case using one or a combination of some of the traditional methods of repair involved tearing out walls and pipes and in the case of chemical flushing, chemical agents are used. 

Traditional methods of repair were also found to be expensive owing to the amount of associated �civil work� i.e.: wall, tile and ceiling repair that is needed after accessing pipes behind walls and ceilings. 

In revenue generating properties, such as Hotels, rooms not available for use create a direct revenue loss. 


A simple fact: For corrosion in pipes to take place, water must be in contact with the metallic surface of the pipes. By the application of an epoxy coating on the interior of the pipe, water to metal contact is eliminated. 

The ACE DuraFlo�system of pipe restoration is designed to clean the piping system of encrustation build up and then coat the interior of the pipe with a NSF Standard 61 approved epoxy coating material. Approved for use in drinking water systems. The size of pipes that can be restored using this process range from 1/2� to 4� in diameter. 

As the restoration process is applied to pipes right within the walls it eliminates the traditional destructive nature associated with a re-piping job. Savings in time and costs when compared to a re-pipe are striking. Piping systems are typically restored in ½ the time and with 30% to 60% cost savings over a repipe job. 

In many cases, erosion corrosion caused from burrs, improper soldering, excessive turns in the piping system and �wear� on the pipe walls created by suspended solids can  be repaired by the restoration process. Cleaning will eliminate the burrs and the ridges created by improper soldering. The epoxy coating smoothes out the inconsistent surface of the pipe created by pitting, cavitation, improper soldering and burrs. The epoxy coating is engineered to repair most pin hole leaks in the pipe. 


The appraiser like many other professionals employs in their day to day assignments a number of standards, principles and rules and like many other professionals the appraiser must try to keep abreast of changes affecting those standards of practice. 

The Principle of Change continues to affect the manner in which appraisers perform appraisals. Changes and developments in the real estate field have a substantial impact on the appraisal profession. Changes in the cost and manner of constructing and marketing commercial, industrial, residential and other types of real estate all impact on the appraiser. 

The issue of dealing with so called hidden deficiencies in real estate always seems to come to the forefront after a problem arises. The question of disclosure and what a professional ought to have known or disclosed to his/her client is and will be the topic of conversation and litigation for years to come. We can all be sure of that. 

However, awareness that a potential problem may exist with a buildings piping system, the reasons and the cost to cure are important to be identified and dealt with before your client calls back and asks �Did you consider the cost of a new piping system in your appraisal?�


ACE DuraFlo Systems, LLC
United States and International Headquarters
711 West Kimberly Avenue
Suite 100
Placentia, CA 92870
Outside of USA 1-714-256-0220
Fax 1-714-854-1833
[email protected]

ACE DuraFlo Canada, Inc.
[email protected]


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