Water pH & Your Plumbing

What is pH?

• pH stands for "potential hydrogen". Without getting too deep into the actual chemistry, it's a measurement of the concentration of hydrogen ions present in something - the greater the ion concentration, the more acidic something is. Less hydrogen (and more hydroxide ions) makes a substance more basic (sometimes referred to as "alkaline").
• Many things affect the pH of a water source. The most significant factor is the composition of soil and bedrock that the water is found in, be it a surface water body (the bed/banks of a lake or river) or a groundwater aquifer. Large amounts of decomposing plant matter in a water body can also increase pH through the release of carbon dioxide (which turns into a weak acid in the water).
• Outside of hard science, pH is commonly measured on a scale going from 0 to 14, with 0 being highly acidic and 14 highly basic (chemists will be quick to point out that it is possible to have pH values beyond these numbers, but this has little bearing on "real world" applications). A 7 on this scale means a substance is neutral (having balanced concentrations of hydrogen and hydroxide ions), as is the case with distilled (pure) water.
• The scale is logarithmic, meaning that each jump between numbers represents a tenfold change - a pH of 3.0 is ten times more acidic than a pH of 4.0, and 100x more acidic than a pH of 5.0.

How Does pH Affect Plumbing & Water Quality?

The pH of drinking water is not regulated by the EPA or any other government agency. It's instead classified as a "secondary" drinking water contaminant - contaminants whose effects are aesthetic, cosmetic, and/or technical (potentially affecting water equipment and/or treatment), as opposed to other contaminants that carry health or environmental risks. EPA does however recommend that pH levels fall between 6.5 and 8.5.

Acidic Water (< 6.5 pH)

• The main concerns with acidic water are corrosion and leaching. Besides the obvious potential for leaks in plumbing, there's the even more serious issue of metal toxicity. While acidic water is not itself a health concern, its interactions with plumbing systems and other materials can result in elevated levels of several metals, which can be harmful.
• Cadmium and manganese might be leached from the environment; other metals like lead, copper, iron and zinc might also be environmental, but are more often given up by home plumbing (pipes, fittings, solder, faucets) in the presence of acidic water. Excessive levels of any of these metals in water can result in health problems. While some acidic water may have a sour or metallic taste to it, most of these metals are not usually detectable outside the laboratory.
• As corrosive water eats away at pipes, the dissolved metals that aren't ingested often come to rest at the bottoms of sinks and tubs, potentially staining vulnerable surfaces. With copper plumbing, these stains are blue-green; with galvanized steel or cast iron, you might encounter red or rust-colored stains.
• The corrosive effects of acidic water are for the most part mitigated when plastic plumbing is used for water distribution - PEX and CPVC are not known to be affected by acidic water.

Basic Water (> 8.5 pH)

• Water with a high pH isn't quite as problematic as water with low pH, but does have its issues. Among them is hard water - water with high levels of minerals (mainly calcium and magnesium). Hard water typically has a high pH because the minerals in the water buffer against acidification.
• Hard water is responsible for a number of plumbing problems, ranging from the annoying to the expensive. Behind most issues is limescale (calcium carbonate). Limescale deposits are usually not too significant, at worst ruining finishes and shower doors - and maybe a few washers and seals. In some cases, scale builds up so much inside pipes that water flow is reduced.
• In the worst cases, scale builds at the bottom of tank water heaters or around coils in electric water heaters, causing them to overheat and potentially burn out.
• Water with a high pH might taste slightly bitter, but is not known to have any effects on health - for good or ill. So the next time you see a bottle of "super-hydrating" alkaline water at the store, don't bother - the science just isn't there.

Remedies

• It's fairly easy to test the pH of your water at home using cheap and widely available pH test strips (if you can't find them in the pond or pool supply area of your local home improvement store, try the aquarium section of a pet store). These aren't anywhere near as accurate as lab-grade electrode testers, but will give you a decent indication of where your water's at. We recommend conducting several tests to get a more reliable picture.
• For finer-grained analysis of your home's water - and a far more accurate pH assessment - consider sending your water to a state-certified lab for testing. The EPA website has information on finding such a lab; your water provider or county health department should also be able to point you in the right direction. Be sure to get detailed directions on collection procedures from the lab.
• Your water provider may be able to provide you with detailed information on their water sources, including data on pH and contaminants. Some make their water assessment reports easily available online; otherwise, try contacting them directly.
• Acidic water is typically best treated by an acid neutralizer. These contraptions utilize calcite (calcium carbonate) to increase water's pH - acidic water is fed into a calcite-filled tank and run through the mineral, which dissolves and raises the pH. Some neutralizers use magnesium oxide instead of calcite to the same effect.
• In some cases, chemical feed pumps are used instead. These inject an acid-neutralizing agent into the home water supply (typically soda ash/sodium carbonate or caustic soda/sodium hydroxide).
• Note: Water should be tested for hardness after installing an acid neutralizer. Since they essentially increase hardness to raise pH, it's easy for water to become too hard - in which case you may also require a water softener.
• Basic water is usually only treated when the pH is extremely high (which can be just as corrosive as acidic water) or when the water is also hard.
• Extremely high pH values can be lowered using a chemical feed pump, which injects an acid (usually sulfuric acid) into the home water supply.
• Hard water is best treated with a water softener. These use a process called ion exchange to remove hardness minerals. Water flows through a tank containing a negatively-charged resin, which attracts the positively-charged hardness ions out of the water, thereby "softening" it. A sodium- or potassium-chloride "brine rinse" flushes the hardness ions from the resin.