Piping Technology Review

The following technology review was solicited by a client comparing various piping materials for a high rise residential structure.  The intention of this document was to synthesize a large amount of technical and market information into a concise decision matrix specifically curated for the needs and priorities of the owner)

 Piping Technology Review:

As part of the project for the renewal of the potable water system, this technology assessment report follows on the potable water piping condition assessment and reflects those finding on several available technological solutions.  The HOA Board of Directors will make a decision on their most appropriate solution based on a cost / benefit / risk / reward profile.

The contents of this report were compiled from many sources; a detailed bibliography can be largely found on the project website under the “research” tab.

Three Important Questions

For this assessment, we will use a simple risk management technique that is well known in the insurance and banking industry.  Our simplified form of this technique is called Three Important Question:

In order to manage risk, one must be able to answer all three questions.  If any one of these questions cannot be answered, then we are unable to manage risk.  If, and only if, all of these questions can be answered, then we can take actions to mitigate the risk. The action of reducing the severity, seriousness, or painfulness of something

The best way to demonstrate this technique is to imagine you are crossing the road.  The first question you ask yourself is “can I identify the peril – are there any cars coming?”  OK, so you can see the cars.  The next question is “What is the likelihood that one of those cars will hit me?”  Are we crossing west Harrison street or the I5 freeway? Now you are considering your dash across the road and you ask yourself, “if a car does hit me, what are the consequences?”  If the cars are bumper to bumper gridlocked, the consequences are minimal.  On the other hand, if you can’t see the cars coming and you have no idea the likelihood the car will come and if it hits you, you could die, then you have an unacceptable condition.

Operating Conditions

Most people would view the entire potable water system as a single entity that transports water to various different places.  However, when we apply the 3 questions, we wind up with a very different set of answers.

The Large pipe – 2-4 inches in diameter carries water from the street to the pump room and branches out to feed the risers network.  These larger pipes normally operate at a relatively slower velocity of water than smaller pipes and are not susceptible to erosion. However, they also operate at a higher pressure after the booster pumps from 80 PSI to 200 Psi.

We can therefore identify the risk of an infinite supply of high volume water at high pressure.  While the likelihood of failure is small, a complete rupture of such a pipe would create significant flooding.  However, the flooding would be confined to the parking garage area and perhaps the laundry room and storage units where drains are well placed.  The flood would probably be discovered fairly quick and the fire department or water district would shut off the valve at the street.  Lots of people would be without water.  A pinhole leak would not cause a great deal of damage.

Medium sized pipes include 2” inch vertical risers branching off to I” inch horizontal supply lines that reach each residence.  These lines are also relatively high pressure and hidden from view or inspection behind walls and are not readily available for investigation.  A pinhole leak would soak a smaller area perhaps appearing as puddles, staining on the units below, a hissing sound, humid smell, or the appearance of mold.

A complete rupture would be catastrophic dumping a high volume of water on multiple units to cascade down all of the floors below the rupture.  This is the type of failure that can cause millions of dollars worth of damage.  So the consequences are dire.

Small pipe carries relatively high velocity water and can introduce turbulence, erosion, and water hammers. Small pipes also carry hot water – a condition known to increase the rate of corrosion.  A pinhole leak or a ruptured pipe will likely be discovered and isolated faster and therefore cause less damage.

When we look at the different operating conditions of the potable water system, it is clear that we need to address individual operating conditions as separate problems – at least from a risk management perspective

Potable Water Technologies

For this project, we are evaluating four separate technologies for applicability in the three operating conditions of the structure.  These are (see slide)

No single solution to replacing the potable water system is 100% failure proof.  All existing technologies have advantages and disadvantages in each segment of the system.  Each has limitations, known risks, and unknown risks.  It is important to understand these limitations so that we may accept, avoid, or mitigate risk as best as possible.

(Other technologies such as CPVC and Polybutylene are not discussed here due controversies surrounding those materials which remain unresolved)

How will we do this?  You guessed it; We will ask the three important questions.

Epoxy Pipe Liner – advantages

Epoxy liner is making its mark as a fast and cheap solution for the renewal of potable water system.  Indeed, epoxy is a magnificent substance that has proven itself for strength, adhesion, and durability in countless applications from boat hulls to medical application.

The advantages of the epoxy liner system are that it uses the existing pipes with no tear-out or re-hanging.  The pipe preparation is done with a sand blasting technique and the cure time is a matter of hours.  The image of a smooth, glossy, hard, and inert coating is indeed powerful

Epoxy Pipe Liner – disadvantages

Unfortunately, there are substantial risks that must be understood and accepted because potential problems will be so difficult to mitigate.

From tests that we have conducted and case studies that we have published for a galvanized steel renewal in Epoxy, as well as a long list of established research, the epoxy lining process is very vulnerable to workmanship quality.  A great deal of information about the existing condition of the pipe, as well as the amount of material that the epoxy process will be removed by the sandblasting, are essential components in addition to a final inspection process.

We have established that a poor epoxy application may likely in precisely the locations where the pipe itself would likely fail.  A chain is only as strong as it’s weakest link

New Copper Pipe – advantages

Copper emerged as a common piping material about 40 years ago as the replacement material for Galvanized steel.  Keep in mind that Galvanized steel replaced Lead pipe which replaced wood stave pipe and open aqueducts prior.  We are now at an age where serious replacements for copper are emerging.

However, one very important advantage of copper is that it has been extensively researched. Under perfect circumstances copper corrodes at 1-3 ten thousandths of an inch per year.  A 1/32 of an inch of copper would take over 300 years to corrode through. This is fact because corrosion in copper is very to measure; a simple current meter can easily measure electrons leaving copper under various conditions for a definitive quantification of corrosion. Therefore, the things that make copper fail are very well known. A successful copper piping requires the mitigation of those known problems.

Additionally, all plumbers now and in the foreseeable future know and understand how to work with copper.  It is relatively plentiful, easy to purify, and holds a premium market valuation in real estate.

New Copper Pipe – disadvantages

However, the vulnerabilities of copper are not trivial. Rapid corrosion and pitting failures have been known to occur where known vulnerabilities are not mitigated.

The main protection for copper is a layer of natural corrosion that forms to protect the raw material.  Naturally occurring organic solids help copper to form this protective layer.  Anything that disrupts or attacks that protective layer will also attack the base copper.

The protective layer of copper is vulnerable to poor electrochemistry such galvanic potential (due to contact with dissimilar metals) or improper grounding from a water heater or plumbed appliance.

Water chemistry can have a direct impact on the protective layer in copper as well. Notably, chlorine readily exchanges electrons with copper, which is accelerated in hot water and accelerated again in overly acidic or alkaline water.  Chlorine is an important additive for a municipal water supply with very important health and safety functions.

Workmanship can have a direct impact on copper longevity since the flux used in soldering the unions can be highly corrosive if used incorrectly, Excess solder within the pipe can cause turbulence that break down the protective layer.  Incorrect pipe sizing can create a high-velocity situation that breaks down the protective layer and leads to erosion corrosion.

Finally, the copper itself must be free of contaminants in the raw material or resulting in the production and manufacturing process.

Corroding copper is not only bad for the pipes but copper ions can attack downstream plastics such as polypropylene and polyethylene (PEX) .  A plastics failure may not always be attributed to a copper failure so root cause is often difficult to find later.

New Polypropylene Pipe (Aquatherm) – advantages

Polypropylene is a class of plastics that includes polyethylene that relies on stabilizers to accomplish its formidable characteristics.  The polypropylene molecule is comprised of only carbon and hydrogen – so nothing bad can leach from it.  Polypropylene is used in thousands of food grade applications and is very well studied.  It’s use as a piping material is not new, however, it appears to be emerging as a strong alternative to most other plastic potable water pipe solution.  Aquatherm is the supplier of note here and they succeed because of their ability to support projects with sufficient and diverse inventory, complete fittings, tooling for creating fusion welds, as well as training and technical support for field applicators.

We chose polypropylene for this technology assessments instead of Polybutylene or CPVC simply because it was surrounded my much less controversy regarding leached chemicals and embrittlement failure and stress cracking, etc.  Polypropylene has the advantage of being a very simple material with very simple characteristics; It is light, it fuses perfectly when heated and connected and it has great shock, noise, and thermal properties.  There are very few known failures in a potable water system and many high profile projects from world-class designers use the Aquatherm brand.

New Polypropylene Pipe (Aquatherm) – disadvantages

Polypropylene appears to be highly vulnerable to the witches brew of copper ionization, hot water, and aggressive water chemistry.  While it may be easier to conceptualize a plumbing job in Polypropylene, a good deal of planning is needed get the material in the right position for a fusion joint.  Crooked joints are said to hold tight if they pass a pressure test, however, it would seem important that they are plumbed straight and true.

Possibly the greatest disadvantage with the Aquatherm product is the sole source out of Germany.  Any piping project is hoped to last 50 years or more, but a lot can happen in 50 years and if Aquatherm is not around, then getting fixtures or finding trained personnel could be a problem.  Aquatherm is a proprietary product with the addition of composite strengthening fibers, as such, it would not likely be prudent to try to fuse any other brand of polypropylene to Aquatherm.  If the tools are not available in 50 years, then a repair, upgrade, or expansion could be thwarted.  As we will see in the mitigation section of this report – we have no control over Aquatherm’s future so we need to amplify the risk of the sole source material and fixtures.

Cross linked Polyethylene – advantages

Cross Linked Polyethylene is a modification of polyethylene plastic commonly found in children’s playground equipment.  Cross linking means that the individual ‘mers’ in the polymer are bunched up into knots instead of aligned in direction.  This allows the material to return to its original size and shape after being stretched.  This is great for holding on to fittings, bending around corners, and expanding under pressure, heat, or even freezing conditions.

PEX is very fast to install and can be thread through walls without having to necessarily cut out large sections of wall board.  Connections can be visually inspected with great reliability and precise measurement is not a critical as other products.  PEX has been widely in use for several decades with broad acceptance in the market and universal familiarity in the plumbing trade.  Many different companies support the PEX products with accessories and connectors such as manifolds, hangers, and specialty adapters.


 Cross linked Polyethylene – disadvantages

PEX is clearly not without controversy. The two primary issues regarding PEX are associated with some fittings and chemical leaching.  At least one class action lawsuit was filed against the makers of a particular brass fitting that was failing in service causing substantial property damage.  The root cause was found to be the dezincification – meaning that the zinc corroded out of the allow and left the remaining copper porous and weak.  Most of these fittings were found in big box hardware stores and made cheaply overseas.  This suit was settled for 90 million dollars or so and the problem is now easily avoidable.

PEX was also found to leach harmful chemicals such as MBTA, TBA, BPA, and other chemicals that are considered toxic.  The State of California has banned PEX in all building structures.  It is now known that of the three types of PEX (called type A, B, or C), type B is the only formulation that does not have any leaching considerations.  As such, this problem is also easily avoidable.

The stabilizers in PEX are highly vulnerable to UV radiation – while they say that some exposure is acceptable, we advise that all precautions are taken to shield this material from UV rays.  PEX is also known to be destabilized by chlorine in the water chemistry as well as copper ions produced by failure corrosion in upstream copper.  As with Polypropylene, these factors are amplified by aggressive and hot water.

Risk Mitigation

Mitigation is the act of reducing the severity, seriousness, or painfulness of something.  It is our hope that the following section can mitigate your reaction to what has been presented so far.

So far, this discussion has been all about identification of the risk exposure, estimating the probability that such risks may manifest in this project.  Then we consider the consequences if the risk does actually occur.  This next section we will discuss ways in which we can reduce the severity of the vulnerabilities for each material

Mitigating Epoxy Liner

The epoxy application process will remove material from the existing pipe during preparation, as such, it is essential to know how much material remains since the integrity of the system will still depend on the integrity of the pipe itself.

Regarding epoxy liner, the American Society of Testing and Materials publishes F2831-12; Standard Practice for Internal Non Structural Epoxy Barrier Coating Material Used In Rehabilitation of Metallic Pressurized Piping Systems.  This document compiles all of the governing documents for epoxy applications as well as specifies acceptable testing standards for adhesion and substrate preparation.  Independent Engineering oversight should be applied to the installation of this product to witness compliance with ASTM F2831-12

Any respectable epoxy applicator will have an in-depth quality manual that specifies each step in the process with decision trees, flow charts, and check lists.  Moral hazard does exist because it is very easy to hide poor workmanship and profit may be directly correlated to skipping steps.  A random sample of epoxy shots must be tested for adhesion per ASTM F2831.  In addition, a section of pipe should be removed and split open for deep inspection by a third party.  This should be done while the applicator is on site to re-coat the repair.

Finally, we call attention to the epoxy paradox: in the event that an application failure – or future failure – is found, then what? The biggest problem with Epoxy is that there is no contingency plan for any failure of any installation, expansion or repair of the system, or even the replacement of valves in the future.  Once the continuity of the epoxy is compromised, corrosion will re-occur.  The epoxy cannot be removed and a re-pipe is therefore inevitable…so why not just re-pipe to begin with?

Mitigating New Copper Pipe

As mentioned, the possibility that a copper piping system could endure for a very long time should be attractive to any homeowner, Condominium Association  or property manager.  The problems are well known and well studied so our first steps in mitigating the vulnerabilities are clear-cut.

All plumbers should have a refresher course or master plumber testing in the standard practices of soldering connections and the application of solder flux, specifically per ASTM B828 and ASTM B813 document.  Review of these documents is essential even if the plumber may resist simply because the consequences of any failures in workmanship can be catastrophic.

The material specified for the job must be verified to conform to material specification ASTM B 88.  This standard will eliminate the likelihood that cheap ‘high- zinc’ alloy would placed in the structure.  Many failures in new developments have resulted in contractors cutting corners with less expensive materials.

Most utilities will introduce chlorine into the water supply and an essential anti-microbial and disinfectant for community safety.  By the time that the water reaches a structure, the chlorine level has dropped significantly.  It is essential then to periodically test the chlorine level at the mains.  If it is too high, there may be ways to consume additional chlorine prior to entering the potable water system.

Natural organic compounds (such as calcium carbonate or magnesium) that appear naturally in above ground public water sources are essential to create the initial protective patina on the copper surface.  Deep-water wells may lack these essential components.  PH balance most be close to neutral, neither too acidic nor too alkaline (PH).

Finally, engineering design must use correct sizing and proper routing to avoid high velocity flow rates and to eliminate the stagnation of water in the system; each of these conditions can result in breakdown of the protective coating that naturally forms on copper.

Nearly all vulnerabilities are known for a copper installation and careful foresight in using expert corrosion / MEP opinion can vastly reduce the already rare occurrence of early copper pipe failures.

Mitigating Polypropylene

Polypropylene is an attractive alternative to consider, especially in situations where pricing is most favorable.  Most of the material mitigation strategies would be similar to PEX, watch the water quality for that known witches brew of aggressive, ionized, and hot water.

The supplier issue is not trivial.  Nobody can see 50 years into the future what repairs or changes may be required for the structure and if Aquatherm will even exist, especially is another technology should arrive and bump Aquatherm out of the market.  After all, 50 years ago, most TVs were black and white and commercial airplanes used propellers.

Using polypropylene in the largest tubing where fewer connections would be required and where future replacement may be least expensive may mitigate this problem.  Aquatherm does have excellent properties for larger pipes; ability to withstand cold temperatures, collision resistance, upstream of copper, and visibility.  Riser use may be equally safe since established connections are unlikely to change over time and access doors provide visibility, as long as upstream pipe is not copper.


Mitigating PEX

PEX is a very important technological advance in plumbing technology.  One good thing about class action lawsuits is that they tend to flush out problems on an industry wide basis as a wealth of research, case studies, and innovation hits the market. While unknown problems may exist, a fairly long usage history combined with accelerated laboratory use cases minimizes this likelihood.  As always, it is prudent to take care in avoiding known problems.

Type B PEX is not known to be vulnerable to the leaching concerns as type A and C.  As such, only this product should be specified for this project based on current information.  ASTM F2023 provides a basis for determining the impact of the existing water chemistry a specific project on the likelihood of oxidation failure.  All fittings must be sourced from a reputable supplier and labeled with a LZ (low zinc) production code.

From factory to fixture, all UV radiation exposure must be monitored and minimized, if not eliminated.  Finally, an access panel should be installed near the main resident manifold so that a periodic visual inspection can be performed to identify possible degradation well into the future.  PEX may be listed as a separate line item on the reserve study and hot water lines may be replaced on a more frequent schedule than other parts of the system.

Risk Matrix

This risk matrix compares the 4 different technologies against the three important questions and the ability to mitigate known problems.

For epoxy; it is impossible to perform a 100% visual inspection of surface preparation and adhesion.  A destructive test must be performed and there is no way to re-work a poor application except by re-piping.  The likelihood of a failure is high based on research conducted by our team and a moral hazard exists for the applicators to shortcut the process.  The consequences of a failure can be catastrophic if existing material is reduced to a point where structural capacity of a pipe is compromised.  Should a riser fail under any physical duress from collision to lightning strike, or earthquake, the damage could amount to millions of dollars.  Therefore, the three risk management questions do not have formable answers and the ability to mitigate failure is deeply inadequate.

Copper offers an acceptable position on the risk matrix chart.  We can identify risk exposures; we understand the likelihood that something can go wrong.  A total rupture is the least likely failure in copper as such catastrophic failures would be rare.  And finally, strategies exist to mitigate most known vulnerabilities.

Polypropylene also offers an acceptable position on the risk matrix – the only exception is a non-trivial possibility that Aquatherm leaves the market.  This is a condition for which we have absolutely no control over.  As such, we are unable to mitigate this risk.

Finally, PEX also offers an acceptable position on the Risk Matrix. We can see the risk exposures; we understand the likelihood that they will occur. Since it would not be used on risers or mainlines, the consequences of failure will be localized and likely contained. We know enough about PEX to mitigate known vulnerabilities


Risk matrix chart has been updated to reflect additional information about the Aquatherm product which lowers the likelihood of long term maintenance and availability.  This analysis is presented in document found here; Aquatherm Research 2.0