In setting up a chemical feed system, there are three important components to consider. The chemical, chemical feeder and the chemical controller all must be compatible and they all should be certified to work together safely and effectively. Chemical feeders are designed for certain types of chemicals (solid vs. liquid) and even specific chemical formulations (trichlor vs. cal hypo). Using the wrong chemical in a feeder may result in underdosing or overdosing the chemical, and even lead to explosions.
The first thing to consider is the chemical that is being dosed and the target range. Disinfectants, algaecides and other biocides are required by federal law to be registered with the U.S. EPA. They should come with an EPA label stating that they are authorized for use in pools or spas at specific dose ranges. Beyond EPA registration for disinfectants and algaecides, there have been no standardized requirements or review mechanisms for pool and spa chemicals. But that is changing. The new edition of NSF/ANSI 50 contains a new health effects assessment process for pool and spa chemicals. While only a few chemicals are certified today to NSF/ANSI 50, over the coming months and years we expect the majority will be certified. These requirements ensure that the ingredients in a treatment chemical will not cause adverse health effects.
It’s also important to assess the expiration dates and periods prior to ordering chemicals. It does no good to order a two-year supply of treatment chemicals if they expire in six months. You should also be aware that not all brands of a specific chemical are the same. You may think sodium hypochlorite is always the same no matter where it comes from, but different brands vary in concentration as well as purity. Solid chlorine tablets such as calcium hypochlorite vary by brand as well. The leading brands vary in erosion rates by significant margins.
When choosing a chemical feeder, pick one that is designed for the specific chemical you are using. Many manufacturers of chemicals also sell chemical feeders or recommend a specific chemical feeder for use with their product. Using the wrong brand tablet with the wrong feeder could result in under- or overchlorination. Using the wrong type of chemical (such as trichloroisocyanurate in a calcium hypochlorite feeder) could result in an explosion. Also make sure that the chemical feeder is certified to NSF/ANSI 50. This standard requires chemical feeders to be tested with the manufacturer’s recommended chemical for durability with life cycle, pressure and performance tests. The Model Aquatic Health Code requires chemical feeders to be certified to NSF/ANSI 50.
The MAHC also requires that chemical feeders used with automatic controllers utilize controllers that are certified to NSF/ANSI 50. This includes chemical resistance and life-cycle tests, as well as measurement accuracy.
Finally, be sure to monitor the chemical concentration at start-up and several times during the day.