Going to the source: knowing the properties of your source water can help you determine which chemicals to use for disinfection and pH adjustment - service

Most service technicians know how sanitizers, pH, calcium hardness and total alkalinity (TA) affect pool water chemistry. However, water experts say many overlook the most prominent influence on those parameters: a pool's source water.

"One of the biggest mistakes most technicians make is that they don't bother to check or monitor [source] water," says Wally James, president of Con-Serv Associates in Powder Springs, Ga.

The properties of the source, or "makeup" water, not only affect how the water is balanced, but actually can dictate which chemicals should be used to sanitize the pool and to maintain proper pH and TA levels.

When called to a job site, source water properties are "the first thing I want to know," says James, who consults on aquatic design, construction and maintenance. "If that's causing a problem [and we don't check it], we can beat ourselves on the head for a long time and never solve the problem. It is truly amazing how many people don't check their makeup water."

Know the source

Kent Williams, a commercial pool consultant based in Newcastle, Calif., agrees. "If you don't know your source water, you don't know your pool," Williams says.

Knowing the source water means testing for water properties that affect pool chemistry. Experts recommend testing the source water for pH, TA, calcium hardness, chlorine content and metals such as iron, manganese and copper.

Complete water analyses also can be requested from the local municipality. The analysis should include the aforementioned properties plus total organic carbon, which may reveal whether there will be a higher sanitizer demand, according to Wolfram Hartwig, Ph.D., manager of Ozone Systems for ES, a division of Neuman Pools in Beaver Dam, Wis.

Municipal water districts are required to provide this analysis, says Hartwig. "It's a federal mandate under the Safe Drinking Water Act monitored by the EPA," he says.

Hartwig explains that there are three basic types of municipal drinking water:

(1) surface water, which is drawn directly from a river, lake or reservoir;

(2) ground water, drawn from a well or an aquifer; and

(3) ground water under the influence of surface water, usually known as "water under the influence."

Water under the influence occurs when a well is drilled near a lake, and lake water infiltrates the well. According to drinking water regulations, water under the influence must be treated as surface water, which means it must be filtered. All surface water requires filtration, but pure ground water does not.

Knowing the source water properties throughout the year can be a tricky proposition if the municipality switches its sources.

"If the source water has a single, steady source then ... you have a fairly reliable way of determining the water you use," says Hartwig, who is also a water chemistry consultant for Water Technology Inc., an aquatic planning, designing and engineering firm in Beaver Dam, Wis. But, he says, "there are municipalities that switch water on a seasonal basis. For example, in Minnesota, in winter, they pump ground water. In the summer, they use surface water. This will, of course, drastically change the water chemistry."

In San Diego, water supplies frequently alternate between reservoirs and water from the Colorado River. Local water tables, which change throughout the year, dictate which source is operating at any given time, says Richard Robert, vice president of Knorr Systems in Santa Ana, Calif., a commercial pool design, service and equipment firm.

If you have taken a job or a route in a new area, you should immediately determine whether the municipality switches water sources and, if so, when the switch takes place. If the city draws from wells, it may rotate use of the wells during periods of equipment maintenance or when aquifer levels change.

If you are familiar with the source water, periodic checks will suffice. If you know the source water to be stable, says Hartwig, "you only need to check once a year. The vast majority of [water districts] have a stable supply."

Some experts warn, however, that being overly vigilant with your testing is not necessary. Sudden, unexplained changes in the pool-water chemistry should be a warning that it is time to check the makeup water.

"You'll see it in the disruption of the normal process you're used to," James says. "Inexplicably, the water will get cloudy, turn a color--maybe green or reddish brown. All of a sudden, chlorine consumption may go sky-high, pH is bouncing all over the place and you can't control it."

Making adjustments

Balancing pool water is a lot easier if the properties of the source water are allowed to dictate the chemicals used. "The treatment system should be tailored to the makeup water," Hartwig says.

Sometimes source water lacks properties needed for good water balance and you'll need to adjust to it. For example, "City water is not always good, pool-wise," says Alvaro Mendoza, president of CES, a provider of automated chemical control and filtration packages for commercial pools based in Jupiter, Fla. "We like to ... match the sanitizer with the deficiencies of the source water."

If the source water registers low levels of calcium hardness (aka soft water), it's undesirable for pool water.

"For drinking water, the ideal water is somewhat soft," says Hartwig. "Ideal drinking water has [a calcium hardness of] 100 to 120 ppm. For pools, we're looking at something around 300. Pool water is supposed to be harder."

0Mendoza recommends calcium hypochlorite as a sanitizer for pools with soft water sources because it adds hardness.

If the water is hard--containing high levels of calcium hardness--and you enjoy the convenience of cal hypo, you can still use it.

"You might have to run different chemical levels, like a lower pH and low alkalinity, to accommodate the higher calcium," says Mendoza.

For overly hard water, a better sanitizer choice is sodium hypochlorite (bleach).

In some circumstances, the conditions of the source are so extreme that they render chlorine-based sanitizers ineffective.

"If we have a constantly rough condition with the makeup water, it may very well justify [adding] an alternative sanitizer," says James, who lists ozone, ionization and UV light as potential alternatives.

Of course, the effectiveness of any sanitizer hinges on proper pH levels. The properties of the source water dictate the pH-correcting methods as well.

To adjust the pH in water with low TA, experts recommend using carbon dioxide because it raises the alkalinity. With source water that contains high TA levels, you would be better off with muriatic acid, which lowers pH.

Williams relates the story of a public pool in Northern California with a TA level of 650, the highest he's ever experienced. It turned out that the pool's source water had a TA of 150, and operators used CO2 to correct pH. The CO2, of course, kept raising the TA.

Operators used CO2 because the county required excessive safety precautions when using muriatic acid, and the technicians didn't want to hassle with the precautions. Williams says this was a prime example of choosing a chemical without checking its appropriateness in relation to source water.

RELATED ARTICLE: The first tim.

When filling a pool for the first time, or filling it after replastering, check the makeup water for metals, which can stain the new plaster.

If the water does have a high metal content, experts recommend using a sequestering agent to keep the metals in a dissolved state.

"That's certainly a big deal because [the customer] hates to spend all that money to have [the pool] stain the first day you fill it," says Richard Robert, vice president of Knorr Systems in Santa Ana, Calif.

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