The Study “Drinking Water Quality Performance for Newly Installed Polypropylene and Crosslinked Polyethylene Plumbing Pipe” questions the drinking water quality of plastic piping.
Many of the clients we see in our architectural practice have health concerns or are otherwise concerned about using safe, non-toxic building products. While air-borne substances get the most attention, there is reason to be concerned about less-than-healthful water-borne substances. To be sure, the vast majority of people need not be concerned with the quality of their drinking water. But for those with chemical sensitivities or who are hyper vigilant about the long-term health implications of the water coming out of their tap, the issue is not trivial at all.
The following materials are most commonly in use for domestic water piping:
-Polyvinyl chloride (PVC)
-Chlorinated polyvinyl chloride (CPVC)
-Cross-linked polyethylene (PEX)
Galvanizing involves the application of molten zinc to pre-formed steel pipes to provide a corrosion resistant coating. However galvanized pipes in old buildings were manufactured using zinc containing high levels of lead, a common impurity in the zinc. It was not until 1986 that Wheatland Tube Company became the first galvanized pipe manufacturer to be certified to ANSI/NSF Standard 61 for its hot dip galvanized pipe. Galvanized pipes are still common in older homes and many commercial buildings. Galvanized pipes will corrode over time, as indicated by the following symptoms:
- high levels of zinc or iron in tap water
- “metallic“ taste of the water
- poor water flow due to blockage from mineral buildup
- discolored water (brown, red or yellow water)
Modern versions of galvanized pipe are considered to be a relatively safe medium for drinking water. There are, however, potential health concerns if the water supply is corrosive due to low pH. Public water supplies treat their water to make it essentially non-corrosive—so this should not be a concern if you are on a public water system. The concern is not for zinc or iron that may be leaching from the pipe, but for lead and especially cadmium, two other heavy metals that may be present as impurities in the zinc used for the galvanizing process. If you are on a private well with galvanized pipe plumbing and the water frequently has a slightly bitter taste, you should have your water tested.
Historically, copper piping replaced galvanized steel in general use and is generally regarded to be a safer medium. However, studies have found that copper in drinking water can add 4 to 45 percent more copper to a person’s diet than from food sources. Absorption studies indicate that the body excretes about half of ingested copper, which offers some protection against copper poisoning. Copper is widely distributed within the tissues of the body, but accumulates primarily in the liver and kidneys.
Copper rarely occurs naturally in the source water supply for drinking water systems. Most copper contamination takes place at some point in the water delivery system. This occurs as a result of micro-corrosion of the copper pipes or fittings, which are widely used in household plumbing. If incoming water is below pH6.5, or if lead solder was used to join pipe segments, copper and/or lead can leach into drinking water.
Low concentrations of copper in drinking water may not noticeably alter the taste, color or smell of water. At low concentrations, copper in drinking water may cause no health symptoms. At high concentrations, it can cause a bitter metallic taste in water and result in blue-green stains on plumbing fixtures. At high concentrations, copper in drinking water may cause symptoms easily mistaken as flu or other illness.
The National Academy of Science recommends 2-3 mg of copper in the daily diet. A single dose of 15 mg of copper can cause nausea, vomiting, diarrhea, and intestinal cramps. Severe cases of copper poisoning have led to anemia and to the disruption of liver and kidney functions. Individuals with Wilson’s and Menke’s diseases (genetic disorders resulting in abnormal copper absorption and metabolism) are at higher risk from copper exposure than the general public, and can have serious health problems.
Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC):
PVC (used for cold water only) and CPVC (used for both hot and cold water) have been around for years, and both are approved for use with drinking water. Neither can be described as environmentally friendly from a production or recycling standpoint.
Leaching studies commissioned by the State of California and conducted by UC Berkeley found that CPVC plumbing pipe systems might leach potentially toxic chemicals such as chloroform, tetrahydrofuran, methyl ethyl ketone, acetone and organotins into drinking water. These chemicals may cause cancer in humans or other serious health impacts.
PVC is also a suspected endocrine-disrupting chemical. Endocrine disruptors interfere with our body’s complex and carefully regulated hormonal messenger system by mimicking, blocking or altering hormonal levels, thus affecting the normal functions controlled by these hormones.
Cross-linked polyethylene (PEX):
PEX tubing is widely used to replace copper in plumbing applications. One estimate is that residential use of PEX for delivering drinking water to home faucets has increased by 40% annually, and there is substantial evidence that PEX is or will soon become the dominant technology for carrying water in homes and businesses in the next decade or so.
During the Engle process of producing PEX piping, chemical byproducts are often left behind in the pipe. The most prominent are methyl tertiary butyl ether (MTBE) and tert-butyl alcohol (TBA). The amount these chemicals can leach into potable water is uncertain, but test of pipe by one manufacturer showed MTBE levels of 17 parts per billion (ppb) and TBA levels at 6900 ppb.
According to the United States Environmental Protection Agency (EPA), MTBE can be a carcinogen when high levels are inhaled. As far as ingesting MTBE, the EPA has no definitive data on the health effects and according to the EPA’s website, “there is little likelihood that MTBE in drinking water will cause adverse health effects at concentrations between 20 and 40 ppb or below.” However, at these levels, MTBE can still make the water undrinkable due to its offensive taste and odor. TBA has been shown to cause cancer and hyperplasia in mice and rats during lab studies.
A relative newcomer to the U.S. market, polypropylene pipe (PP) has a 30-year history in Europe where it generally enjoys high marks for water safety. It’s a rigid plastic pipe, like CPVC, but it’s not joined together with chemicals. Instead, heat is used to melt the mating ends and fuse them permanently together, thus eliminating chemical bonding agents as a source of water contamination.
From the Study “Drinking Water Quality Performance for Newly Installed Polypropylene and Crosslinked Polyethylene Plumbing Pipe”.
A recent study “Drinking Water Quality Performance for Newly Installed Polypropylene and Cross-linked Polyethylene Plumbing Pipe” found significantly lower levels of volatile organic compounds (VOCs), organism regrowth, and odor impact in PP as compared to PEX piping.
For further reading: