Understanding the differences between pool and hot tub water quality

Other sanitizing/oxidizing methods

Ionization is a method that generates copper (Cu) and silver (Ag) ions to provide algaecidal properties and extremely limited biocidal properties. It is important to remember ionizers (a.k.a. mineralizers) are not oxidizer/sanitizer systems. Despite marketing claims, ionizers require a small amount of chlorine to provide a sanitizing/oxidizing residual in hot tub water. Caveat: Do not use bromine with ionizers as silver bromide may form. This chemical compound is potentially hazardous if ingested and can stain acrylic/fibreglass shells.

Polyhexamethylene biguanide (PHMB) products are used primarily for microbiological control. Because PHMB lacks oxidation capabilities, hydrogen peroxide (H₂O₂) needs to be added as an oxidizer/shock to eliminate any organic buildup. It is important to note PHMB is not compatible with most halogen-based products (e.g. chlorine, bromine, ozone, monopersulfate, and copper-based algaecides).

Potassium monopersulfate (KHSO₅) is an oxygen-based oxidizer (not a sanitizer) used to remove organic buildup, prevent new combined chlorine formation, 
and kick start the bromine cycle. This product dissolves quickly, produces no odours or irritation, and bathers can get back in the spa within 45 minutes to an hour after it is added. Caution should be used with monopersulfate as it has an extremely low pH (2.3), and overdosing can lead to equipment corrosion and/or water balance problems.

Knowing these hot water chemistry basics will help 
to ensure the water in a customer’s hot tub is in pristine condition. A happy customer can be a company’s best source of advertisement.

Wayne J. Ivusich, BA, MS, CPO,® CPI,™ NSPF®I, is the director of education for Taylor Technologies Inc., in Sparks, Md. 
He has been in the pool/hot tub industry for 25 years and has fielded technical questions from health officials, service technicians, distributors, dealers, and pool and hot tub owners about basic and advanced water chemistry. Ivusich, an experienced conference speaker and recognized industry expert, is a Certified Pool Operator (CPO®), a National Swimming Pool Foundation® Instructor (NSPF®I), and a member of the NSPF® Education Committee. He received his bachelor’s degree in 1987 
and his master’s degree in 2007 from Towson University 
in Towson, Md. He can be reached via e-mail at wayne@taylortechnologies.com.