Aggressive, corrosive, low pH water - acidic water:

This article describes effects of low pH, acidic or corrosive water on building piping, leaks, dissolved copper, health hazards, and the plumbing system in general. We describe how to detect corrosive or aggressive water and what should be done about it.

The Langlier index is defined and its use in evaluating the corrosivity of a water supply is explained. This article also describes other factors in the formation of leaks in building water piping including scouring, debris, & the effects of hot water on water pH. The article links to more information about green stains traced to the water supply.

Acidic water & copper pipe corrosion/leak risk / leak prevention

Corrosive water is responsible for health effects of increased lead, copper or other contaminants in drinking water and corrosive water in building plumbing & heating systems is also responsible for costly leak damage.

Article Series Contents

• CORROSIVITY or ACIDITY of WATER
  • CORROSIVITY PROBLEMS in WATER SYSTEMS
  • CAUSES of CORROSIVE WATER
  • COPPER IN WATER, HEALTH EFFECTS
  • pH of DRINKING WATER, HEALTH EFFECTS
  • LANGLIER SATURATION INDEX LSI
  • LEAD IN DRINKING WATER, HOW to REDUCE
  • LEAK INSPECTION of WATER SYSTEMS
  • OTHER CAUSES of PINHOLE LEAKS in COPPER PIPES
  • OTHER CAUSES of PIPE PITTING: pH & HCO₃ LEVELS
  • PINHOLE LEAKS by ELECTRICAL GROUND ERRORS

Problems caused by aggressive / corrosive water

1. Corrosive water invites plumbing leaks or leaks in hot water or steam heating systems, water heaters, pipes, water tanks, other metal components in the water handling system that that can lead to very costly damage to the building or its mechanical systems.
   
   Corrosion causes both pinhole leaks and stress cracking in metal components. (Jones 1998, Was 2007).


2. Corrosive water dissolves lead or copper into drinking water, leading to potentially serious health risks. (Isaac 1997 et als)
   
   See LEAD IN DRINKING WATER, HOW to REDUCE for an example of lead contamination in the Flint Michigan water supply.

At "COPPER PIPE PINHOLE LEAKS: cause, cure, prevention" we point out that water chemistry itself can be a source of metal water pipe (and even drain pipe) corrosion.

From our illustration adapted from Environment-Canada you can see a pH scale showing that

• high pH numbers are more alkaline (more basic) while
• low pH numbers mean that a substance (water in our case) is acidic.

[Click to enlarge any image]

Neutral pH values are in the middle of the range. Low pH or acidic water is corrosive or is referred to as aggressive water.

Before we explain the details of the causes and effects of aggressive or corrosive water, here is an except from our copper pipe leak discussion:

If the pH is low <6.0, the hardness low generally<50ppm, the alkalinity low generally <40ppm, the water could be considered extremely “soft” and aggressive to the home’s metallic plumbing system.

If the chlorides are elevated >100ppm this would only compound the problem. The water should be treated to make the water less aggressive by raising the pH, alkalinity or hardness. - CT DOH.[1]

Top Ten Factors Affecting the Corrosivity of Water

1. Bacteria level in water (bacteria such as sulphur reducing bacteria (SRB) increase the corrosivity level of water) (Little 2007)
2. Chlorine level in water (higher chlorine levels in water make the water more corrosive)
3. Conductivity of water (higher electrical conductivity means more corrosive; some dissolved salts or metals increase conductivity)
4. Gases dissolved in water (higher levels of certain gases including oxygen or carbon dioxide (CO₂) increase water corrosivity) (De Waard 1975)
5. Mass ratio (CMSR) of chloride to sulfate: a CMSR more than 0.2 but less than 0.5 increases the risk of corrosion; and a CMSR greater than 0.5 when combined with an alkalinity less than 50mg of calcium carbonates (CaCO₃) per liter is likely to be corrosive
6. Solids dissolved in water (higher dissolved solids such as salts and sulfates increase water corrosivity both chemically and by encouraging bio-chemical corrosion)
7. Solids suspended in water (more suspended solids such as sand or sediment and even moving rust particles increase corrosion by abrasion)
8. Water flow rate through building piping (faster flow rates increase corrosive effects)
9. Water temperature (higher temperatures mean more corrosive water)
10. Water pH that is below 6.5 or above 8.5. Low pH (acidic) water is corrosive while high pH (alkaline) water forms scale that can actually protect against corrosion.

Adapted from Sigler & Bauder ret. 2017, Kiene 1998, Oram, Water Research Center ret. 2017 cited at REFERENCES

Other Water Conditions Causing Pitting & Leaks in Copper Piping: pH & HCO₃ Levels

Mattsson et als (1968) provide a helpful elaboration of the causes of failures in copper piping due to pitting and corrosion from which we quote these excerpts:

An investigation of failures of hard-drawn copper water pipes (phosphorus-deoxidised copper) in service due to pitting corrosion was conducted from November, 1962 to February, 1965.

Fifteen cases were reported. All those about which information could be obtained came from hot water installations and occurred in water with a low pH (?7) and a HCO3- content of, at the most, 100 mg/l but generally below 50 mg/1.

Failures not due to pitting corrosion (i.e. caused by erosion and corrosion or corrosion fatigue) occurred in waters with a higher pH and higher HCO3- content.

A laboratory investigation into the ability of the corrosion products to counteract further corrosion in different types of water was also carried out, using an electrolytic cell which, in principle, was a model of an active pit in a copper tube. This led to the following conclusions, which are in good agreement with the results obtained from the examination of service failures:

If the pH value of the water is high enough, the copper dissolved by the corrosion can be precipitated as basic copper salt. At low pH values such precipitation does not take place.

If the [HCO₃?]/[SO42?] ratio in the water is high, dissolved copper can be precipitated as basic copper carbonate in the neighbourhood of the corrosion site and counteract further corrosion.

At a low [HCO₃?]/[SO42?] ratio, crusts of basic copper sulphate will be precipitated at some distance from the corrosion site and may lead to a high corrosion rate.

Pitting is not likely to occur in hot water tubes of hard copper if the pH is ? 7·4 and the [HCO3?]/[SO42?] ratio ?1 (the concentrations given in mg/1). The critical values mentioned are approximate and may be adjusted in the light of future experience. - [14] "Pitting Corrosion in Copper Tubes – Cause of Corrosion and Counter-Measures", Mattsson, E.; Fredriksson, A.-M., British Corrosion Journal, Volume 3, Number 5, September 1968

For our readers who skipped high-school chemistry:

• HCO₃ is an chemical abbreviation for bicarbonate, an anion of carbonic acid from which one hydrogen atom (H) has been removed. Synonyms include hydrogen carbonate or hydrogencarbonate. You can see from the formula that an HCO₃ molecule contains one Hydrogen atom, one Carbon atom and three Oxygen atoms.
• SO42 in the quote from Mattson might be written more commonly as SO4-2, is a sulfate ion, more often y seen as HSO_4-2 hydrogen sulfate, or in water systems more likely as Ca(HSO₄)2 Calcium hydrogen sulfate or as Magnesium Hydrogen Sulfate Mg(HSO₄)2

Continue Reading at PINHOLE LEAKS by ELECTRICAL GROUND ERRORS

More about Acidic Water & Acid Neutralizers on Building Water Supplies

The following articles on acidic water and its corrosive effects are by Steve Bliss, editor of our sister website BuildingAdvisor.com

• ACID NEUTRALIZERS (in WHOLE HOUSE WATER TREATMENT) - retrieved 2018/01/14, original source https://buildingadvisor.com/buying-land/water-wells/whole-house-water-treatment/#jump3
  
  Excerpts:
  
  Two types of equipment are used in homes to neutralize acidic water that is causing problems, such as blue stains of fixtures and corrosion. The most common system is a neutralizing filter. In the other a chemical feed pump or metering pump is used to inject neutralizing chemicals.
  
  A neutralizing filter runs the water though a tank filled with calcium carbonate or ground limestone, and sometimes magnesium oxide or other minerals for high acidity.
  
  In a chemical feeder, a small pump is used to inject a solution of soda ash (similar to baking soda) and water directly into the well or into the plumbing before it enters the pressure tank. First a small amount of soda ash is mixed with water in a holding tank, and the injection pump is activated with the well pump kicks on.
• HARD WATER, ACIDITY AND TURBIDITY - retrieved 2018/01/14, original source https://buildingadvisor.com/buying-land/water-wells/water-quality/#jump6
  
  Excerpts:
  
  Acidic water, metallic leaching, and lead poisoning. Like water hardness, acidity is a natural condition of some well water that is a nuisance but generally not a health hazard. Water with a pH below 7.0 is considered acidic; above 7.0 it is basic or alkaline. The U.S. EPA doesn’t regulate the pH level in drinking water, but it recommends levels from 6.5 to 8.5.
  
  Alkalinity is not a health problem, but highly alkaline water can make drinks such as coffee taste bitter, cause scale to build up in plumbing; and reduce the efficiency of electric water heaters.
  
  Highly acidic water will leach copper or iron from the inside of piping and deposit blue-green (copper) or rust-colored (iron) scale on sinks, tubs, and other plumbing fixtures. The corrosive effect can also affect metal finishes and lead to pinhole leaks in plumbing over many years as well as a bitter metallic taste.
  
  More ominously, acidic water can leach lead from lead pipes, plumbing fixtures, and solder in copper plumbing.
• TREATMENTS for ACIDIC WATER - retrieved 2018/01/14, original source https://buildingadvisor.com/treatments-for-acidic-water/
  
  Excerpts:
  
  If acidic water is a problem, the simplest approach is to install a whole-house acid neutralizer, which adds a little calcium carbonate to the water. I’ve had a system in a home for a couple of years. In addition to eliminating the blue stains, the water tastes a lot better, due to less dissolved metals in the water.
  
  To reduce acidity, water is piped from the pressure tank to the tall fiberglass tank filled with calcium carbonate (see photo). The multiple shut-offs into and out of the tank, allow for easy flushing of the tank with water flow in either direction.

More Causes of Pinhole Leaks in Copper Pipes in Buildings

Besides corrosive water there are other common and some un-common causes of pinholes or other perforation leaks in copper pipes in building supply and drain piping are listed at OTHER CAUSES of PINHOLE LEAKS in COPPER PIPES

Health impacts of copper on drinking water

Moved: see COPPER IN WATER, HEALTH EFFECTS

Limits for Copper in Drinking Water

Moved: see COPPER LIMITS in DRINKING WATER

Corrosivity & Lead in Drinking Water

See LEAD IN DRINKING WATER, HOW to REDUCE for a discussion of lead contamination in drinking water such as in Flint Michigan in the U.S. - a problem stemming from a combination of corrosive water and lead water supply piping.

Also see LEAD in WATER, ACTION GUIDE.

WHO Advice on Water pH - health effects

See pH of DRINKING WATER, HEALTH EFFECTS

Optimum pH for a Building Water Supply

See pH TARGET for DRINKING WATER, WHO

Acidic Water Treatments to Raise the pH

See pH TOO LOW, ACIDIC WATER ADVICE

Acidic Well Water

Please see pH INCREASE to REDUCE ACIDITY

Water Corrosivity Measurement: Langelier Saturation Index

Definition of the Langlier Index (LI) has moved to LANGLIER SATURATION INDEX LSI

Also see SCALE PREVENTION, WATER HEATER

Water Corrosivity Action Levels in the Langelier (LSI) Index

This topic has moved to LANGLIER INDEX ACTION LEVELS

Also see in that article LANGLIER INDEX ACTION LEVELS.

Inspect copper piping for leaks, corrosion, pinholes & leak risk factors

This discussion is now expanded and found at LEAK INSPECTION of WATER SYSTEMS

Electrical Ground Wiring Errors Can Cause Plumbing Pipe Leaks

Now in a separate article PINHOLE LEAKS by ELECTRICAL GROUND ERRORS we add an electrical ground defect that can cause leaks in metal pipes carrying water, sewage, even air conditioning or heat pump refrigerant.

Effects of hot water on water pH

Please see WATER TEMPERATURE EFFECT on pH

That about exhausts me [DF] on copper pipes, pH, corrosion, copper testing, Langelier index, and treatment for low pH water. Thanks for asking.

...

Continue reading  at COPPER IN WATER, HEALTH EFFECTS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• WATER TREATMENT EQUIPMENT CHOICES - topic home,
• LEAK CAUSES in WATER PIPING
• LEAK TYPES, WATER SUPPLY or DRAIN PIPES - where do leaks occur and how to find them
• PLUMBING LEAK DETECTION METHODS
• PLUMBING LEAK DETECTION & SHUTOFF DEVICES
• WATER HARDNESS: HOW TO MEASURE
• WATER STAINING CONTAMINANTS

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CORROSIVITY or ACIDITY of WATER at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER TREATMENT SYSTEMS

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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