Hot Tub Water Chemistry

Hot Tub Water Chemistry

Let's start with the components of "healthy" water, but don't despair if this looks too technical for you to master. As the descriptions that follow will demonstrate, anyone can maintain a clean, healthy hot tub with a little knowledge and a very small investment of time.

• Chlorine residual (sanitizer): 1.0-3.0 ppm
• Total alkalinity: 80-150 ppm
• pH level: 7.4-7.6
• Hardness: 200-400 ppm
• Total dissolved solids: Less than 2000 ppm

Of course if you use an alternative to chlorine in your hot tub, the appropriate level of that sanitizer would be listed instead.

Hot tub water chemistry is a process of balance. Change one component, even to bring it into a correct range, and you may adversely affect another component, thereby adversely affecting the entire hot tub.

Imagine that the water quality parameters listed above are stones, each of equal size and weight, evenly distributed around the edge of a dinner plate and balanced on one finger. If one stone is doubled in weight or removed, it will change the balance, eventually making the entire plate crash to the ground. So it is with water chemistry a balancing act, with each component working on the others.

This is the "balance" of water chemistry, but what is the "demand" part? Water is a solvent. It will dissolve and absorb any substance until it can no longer hold what it dissolves (called the saturation point). After this, it will "dump" the excess of what it has dissolved (called precipitate). Therefore, you can say that water makes "demands" on anything it comes in contact with until those demands are satisfied.

For example, if your hot tub water is very acidic, it will "demand" to be balanced with something alkaline. If your hot tub is plastered, the alkaline lime in the plaster will be dissolved into the water until that balance is achieved. When the water is no longer acidic, it will start "dumping" excess alkaline material, depositing it on tiles and inside hot tub equipment as well as back on the plaster as rough, uneven calcium deposits.

Therefore, successful water maintenance is the quest for balance between the various demands of each aspect of water chemistry. Let's examine those now.