pH scale for common materials  - pH Standards & Adjustments
Effects, cures for too low pH or too high pH in water

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Recommended pH for drinking water, effects of too high pH or too low pH water - acidic water.

This article provides the WHO guideline for recommended pH for drinking water. We discuss water that is too high in pH and water that is too low in pH. We suggest ways to correct corrosive, aggressive, or too- acidic well water.

This article series 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.

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The World Health Organization, WHO Advice on Water pH - health effects

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Article Contents

Effects of Exposure to Extreme pH Values in Water

What is the Optimum pH for a Building Water Supply?

WHO says in general the optimum pH target for drinking water should be 6.5 - 9.5, adding " No health-based guideline value is proposed for pH." [but they didn't appear to consider the effects of dissolved copper - if it occurs]

Acidic Water Treatments to Raise the pH (lower acidity): Calcite Filters vs. Soda Ash Injection

According to the Clean Water Systems & Stores (who sell this equipment) , calcite neutralizer filters

... will typically raise the pH of the water to 7.0 to 8.0 and add 30 to 100 ppm of hardness depending on the alkalinity and water hardness. [2]

More sophisticated is a soda ash injection system. That approach requires a pump and metering device along with an intermediate tank to give the water enough contact time with the soda ash. And room to store 25 or 50 pound bags of soda ash.

Like some other water treatment systems (like a chlorine injector) the soda ash injector pump is hooked up to run when the well pump turns on. It seems that a soda-ash injector system is recommended when the low pH of water is due to dissolved mineral acids (do you live near a mining site or in New York a natural gas from shale mining operation?).

Chemical Feed / Neutralization Soda Ash: water treatment systems dispensing a soda ash chemical feed are used to correct high water pH (acidic) conditions by injecting a base (soda ash) into the water supply followeed by filtration. Water high in natural acids or high in carbon dioxide (CO2) are acidic and are likely to need a treatment of this type.


Acidic Well Water Advice

Reader question: Sage advice needed about corrosive / acidic well water

I have fairly acidic well water on Cape Cod – pH 6.3. I get a lot of blue stains on bathtubs and sinks, which I assume is copper leached from the inside of the copper water-supply piping. I built the house about 16 years ago and replaced the water heater a few years ago.

Am I at risk of developing pin holes or other damage to the copper plumbing and other equipment, including an electric water heater, boiler, and baseboard radiation?

If that’s the case, what’s the preferred (and cheapest) solution: calcite neutralizer tank, soda ash feeder, or other?

FYI, copper level was last measured at 0.11 mg/L, well below the MCL of 1.3, so I don’t think there’s a health issue. But I figure if copper gets leached from the pipes for enough years, at some point there won’t be much pipe left.

Muchas gracias, Steven Bliss, 4 Burlington, VT


I do not have experience with pH treatment first hand, but it appears to me that the short answer is that for most situations, calcite filters are the easiest and cheapest method of treatment. But certainly experts have been looking at this problem for along time, and continue to research it. See Mattsson et als [14][15].

Before choosing one I'd measure the LANGLIER SATURATION INDEX (LSI) of the water so you can figure out the level of treatment needed and check that against the treatment method proposed.

Incidentally, before water testing or asking your test company about what they commonly find in wells in your area of Cape Cod, don't rule out the water supply itself as contributing to the supply of dissolved copper.

You could easily distinguish between copper from acidic effects on copper water piping and copper in the water supply by comparing two water tests, one taken from in the building (I give some aggressive testing suggestions below) and one taken from water where it enters the building, presumably through a plastic or galvanized iron well pipe (not a copper one).

Until you know the score, if there is a worry that pipes may already be thin or at risk, that's an extra reason to shut off water when leaving the property unattended.

Some of the suggestions at WINTERIZE A BUILDING might help.

Hot water and water pH - what happens to pH when we heat up the water?

You could collect a hot water sample as well, running water until it's hot, but because the "hot" water has arrived fresh from the water heater tank, it has not sat overnight in the piping and so is not such an aggressive test - I wouldn't bother. Not unless your home uses an antique copper water heater tank.

The WHO guidelines for drinking water quality points out some interesting technical detail,including that (at least for pure water) heating the water will decrease the water's pH. A pH decrease of 0.45 occurs when you raise water temperature by 25 deg. C. [13]

If the house has part plastic water supply piping, you'd want to see where the copper is located, calculate (by linear feet of pipe and its diameter) how much cold to run out to be sure you've collected a sample from inside the copper pipes.


Continue reading at LANGLIER SATURATION INDEX LSI or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

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