In The News Eye On Ions How to purify water with copper, silver and direct current. (TECH NOTES by Marilyn Pitts) Among alternative sanitizers, ionizers are probably the least understood. The ignorance is partly the result of the system's own oddness - it sounds so strange, and is so unlike other sanitizing methods - and partly the result of excessive claims made in the past by some manufactures. Ionizers have been promoted as all that is needed to treat spa and pool water. They are not. "It's a supplement to water treatment, not 100 percent treatment," says Dan Katz, president of Pure Water Corp. "It's not a cure-all or a panacea." But while acknowledging ionizers can't cure everything, the manufacturers of these systems say they can reduce the problems and hassles sometimes associated with chlorine and bromine sanitizing methods. According to these makers, using an ionizers cuts the pool-maintenance workload, as well as the chemical expenses. "An ionizer is very simple tool for maintaining water without adding so many chemicals," says Katz. Some chemicals may still be needed: an occasional oxidizer (to help break through the cell membrane of algae and to clean up the cytoplasm left by the bacteria the ions have killed; unlike chlorine or ozone, ions do not break down what they kill) and perhaps a sequestering agent to control scale and a chelating agent to clump contaminants so they can be filtered out. Clearly, effective filtration is necessary if ionization is to be effective; the water's chemical balance is very important too. The two ions that are widely used are copper and silver. Research has demonstrated clearly that copper ions inhabit algae growth in water. (When you add copper sulfate or a copper based algaecide to spa and pool water, you create copper ions.) And some research has indicated that silver ions kill bacteria. In 1962 the U.S. Public Health Service approved silver for use in drinking water. But what exactly are ions? Basically, they are atoms or groups of atoms that have an electrical charge. An atom acquires this charge by gaining or losing electrons. Electrons which have a negative electrical charge, are one of three basic constituents of atoms; the other two are protons, which have a positive charge, and neutrons, which have no electrical charge. The process by which an atom gains or loses electrons is called "ionization". There are a variety of ways it can occur, some quite simple. In fact, ionization takes place when ordinary table salt is dissolved in water; it goes from being sodium chloride to being positive sodium ions (NA+) and negative chloride ions (CL-). For pool and spas, ionization is produced by more sophisticated means. Pool and spa ionizers use electricity to generate metal ions. Water passes through an ion chamber that's plumbed in line with the filter and pump. Inside the ion chamber are two electrodes, set slightly apart and in line with the direction the water is moving. These electrodes produce the ions. During operation, a safe, low-voltage direct current (like several flash light batteries working together) passes through the electrodes. This voltage causes the atoms on the outer surface of the electrodes to shed electrons; the atoms become positive and attempt to leap to the other electrode. Before the ions can make it across, through, the water sweeps them away. Metal of Choice The two most common types of ionizers for water treatment are copper systems and copper/silver systems. Copper systems have copper electrodes and so produce only copper ions; copper/silver systems have one copper electrode and one that's copper and silver, so they produce both ions. For pool and spas, most manufactures recommend the two-ion system. (Copper systems are typically used for such applications as fountains, where corrosion and algae control are the primary concerns). To monitor copper levels, use a copper test kit. The test is colorimetric; just add a reagent to the water sample and check the results against a color chart. The generally recommended copper level would be between 0.3 and 0.4 parts per million, with a total alkalinity reading of 80 to 120 ppm and a pH of 7.2 to 7.6. (It's when these levels are exceeded that copper staining occurs). There are no federal standards for ions in swimming pools, though there are Environmental Protection Agency limits for drinking water: 0.05 ppm silver and 1 ppm copper. (That's why the electrodes are mostly copper). Operation/Maintenance tips Treating scale: An ionizer won't remove scale from pool water, though some manufacturers say that the copper ions do discourage the formation of scale on pool and spa equipment by discouraging the formation of slime that calcium and magnesium salts cling to. To prevent scaling, keep the calcium level below 300 ppm. In hard water areas, that may mean using a sequestering agent. Adding an oxidizer: To control algae more effectively, some makers of ionization systems recommend weekly dosing with an oxidizer. Potassium peroxymonosulfate (vinal lined pools only), at the rate of one pound per 10,000 gallons, is commonly used. Sodium perborate, the granular form of hydrogen peroxide, is also said to be effective. If the pool or spa has an area that needs algae removed, brush the area and sprinkle it with a little potassium peroxymonosulfate. Let the oxidizer work for a while and then brush again. Sodium hypochlorite (liquid chlorine) can also be used ( 1 2/3 to 2 cups per 10,000 gallons). Added in the evening, it will have done its work and be gone by morning. Another method: Every two weeks (or when the water is looking dull) mix 3 to 4 ounces of calcium hypochlorite per 10,000 gallons in a bucket of water and distribute it around the pool. Then follow behind with 1/3 cup of a non-chlorine oxidizer such as potassium peroxymonosulfate. Replacing electrodes: The electrodes in an ionizer will eventually wear out and need to be replaced. How long it will be until "eventually," and how much new electrodes cost, varies greatly. Removing copper stains: If necessary, reduce metal levels and prevent staining by using a chelating agent. Remember, the key to preventing stains is proper water balance.