Hot Tub Chemical Basics

Keeping everything in balance

Hot water chemistry can be broken down into four goals: Kill bacteria, provide bather comfort, eliminate scaling and prevent staining. All four can be achieved by maintaining water balance, using a few commercially available products and a couple of minutes each week for diagnostic testing. 


Killing Bacteria 

Normally, hot tubs use either bromine or chlorine to sanitize water. Both products are available in granular or tablet forms, which are added to the water as directed by the manufacturer.


Personal Comfort 

An important factor in maintaining cleanliness and comfort with your water is pH, a measurement of how acidic or alkaline (basic) the water is relative to distilled water, and is measured on a scale of 0 to 14. Numbers below 7.0 indicate acidity, while numbers greater than 7.0 indicate alkalinity. Maximum comfort is achieved at a pH of 7.5 or slightly alkaline on the pH scale. 


On the other hand, water that is low in pH can destroy the total alkalinity content in the spa water. When this occurs, minor adjustments in pH can have dizzying effects due to the water having very little buffering effect, or resistance to changes in pH. Have two products on hand and test for each: one to raise pH, the other to increase total alkalinity.


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Since a newly installed spa is most likely filled with municipal water of an unknown pH level, a simple test will determine how to initially treat the fill water. If the fill water records a higher pH than the recommended 7.4 to 7.6, it is considered alkaline, or base, and will require an acidic additive to lower the pH into range. Conversely, if the fill water is lower than a pH level of 7.4 to 7.6, then it is acidic. If your water requires adjustment, your neighborhood spa store sells products such as “pH up” and “pH down” to bring your spa water back into the recommended range. 


Eliminating Scaling 

Imagine if the spa were as difficult to keep clean as your shower door. The pesky door buildup is because the shower water is high in mineral content and high in pH. In spa water, keeping pH in the desired range keeps minerals from plating out at the water line unless water is extremely full of minerals. To minimize spa scaling, your local hot tub retailer has products designed to remove minerals from water effortlessly by chemically cementing them into a size that can be filtered out, a process called flocculation or chelation. 


Preventing Staining 

Somewhat related to scaling, spa staining can occur by aggressive water attacking the spa finish and equipment. Specific common causes of staining include acidic supply water and overapplying chemicals. Either way, the effects of aggressive water can be rapid and permanent, so be sure to let your spa dealer know about any visual evidence of staining as soon as it is detected. 

Hot tubs are among the most relaxing and healthful products being sold on the market. Their care is remarkably easy with simple chemical additions, routine testing and the assistance of a reputable spa retailer.

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