A Balancing Act.
Keeping your spa water sanitized is your primary goal. For any sanitizer to work well, however, the water needs to be balanced. Five factors contribute to water balance: pH, total alkalinity, calcium hardness, total dissolved solids (TDS), and temperature. With the exception of temperature, each factor can be measured with a test kit available from a pool and spa supply dealer, as well as some home improvement stores and mass merchants.
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Click on Photos for Next Small Spa Bathroom Gallery ImagesIf the values are on the low side, the results can be metal corrosion, surface etching, and staining. If they are on the high side, you may see cloudy water, staining, and mineral deposits. In either case, soakers are likely to experience eye and skin irritation.
Because a change in one factor can affect the others, your challenge is to balance the water using various types of chemicals, also available from most hot tub dealers. The process isn't as hard as you may think, as long as you understand how each factor contributes to the overall balance.
First, it's important to note the volume of your spa, because the amount of chemicals you'll add depends a lot on how many gallons or liters of water you are treating. The volume of water in a spa is usually noted in the manufacturer's owner's manual, but if you own a custom spa, you may need to calculate its volume on your own using basic geometry. Refer to Calculating the Volume of Your Spa, page 39, for easy-to-follow formulas.
Now let's look at the five water balance factors and how they affect the quality of your spa water. Most of them are easily monitored using test strips.