Drinking Water Treatment pH Adjustment

pH is an indicator of the acid or alkaline condition of water. The pH scale ranges from 0-14; 7 indicates the neutral point. The normal pH range of drinking water is 6 – 8.5. The pH is mostly a result of natural geological conditions at the site and the type of minerals found in the local rock. The pH can also be affected by acid rain. Water with a pH value less than 7 is acidic and tends to be corrosive. Acidic water (low pH) can leach metals from plumbing systems, which can cause pipes to leak. Metals that leach from the pipes (lead from lead pipes or copper from copper pipes) may also cause health problems. Water with a value greater than 7 indicates alkalinity and tends to affect the taste of the water. Alkaline drinking water may take on a “soda” taste. Corrosion problems also can occur in plumbing. The three types of pH adjustment devices are discussed below.

A neutralizing filter is used if drinking water is acidic (low pH). It is a simple treatment device that raises the pH of water by adding a neutralizing material. However, it should be noted that the neutralization process may increase water hardness.

Neutralizing filters are point-of-entry devices that raise water pH to neutral levels (around 7) which reduces or eliminates plumbing corrosion problems. Calcium carbonate treats water with a pH greater than 6 and synthetic magnesium oxide will treat water with a pH below 6.

Untreated water flows through the filter, which is filled with calcium carbonate (limestone) or a synthetic magnesium oxide medium. This material dissolves in the water and raises its pH level.

The neutralization process takes time and in general the flow rate should not exceed 3.0 gallons per minute per square foot of filter bed area. A bed depth of 32 to 36 inches is necessary to provide adequate contact time; shallower beds will not provide sufficient neutralization.

All treatment systems require regular maintenance. The material used in a neutralizing filter needs to be refilled and the filter needs to be backwashed regularly.

Installing a cartridge filter prior to the neutralizing filter will remove solid particles from the water and can help to prolong the life of the neutralizing filter.

The biggest drawback to neutralizing filters is that they may increase or cause water hardness if calcium and magnesium are used in the filter. If hard water becomes a nuisance, the neutralizing filter should be followed by a water softener. If water hardness is treated with sodium, it may be unsuitable for people on a low-sodium diet.

In addition to water hardness, neutralizing filters may also cause water pressure loss due to the fact that the water needs to flow through finely ground neutralizing material.

Neutralizing filters are typically installed after the pressure tank, so neither the pressure tank nor the well pump will be protected from corrosion. If the flow rate is high, a liquid injection system (see below) may be better than a neutralizing filter, as it is installed before the pressure tank and thus provides corrosion protection to the tank and the plumbing system.

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