WATER CHEMISTRY

Water is water, isn’t it? If I can drink the water, why can’t I soak in it? These are good questions, but the answers are not as simple as the questions. As you remember from chemistry, all water starts as H2O. But what happens after that is why all water is not the same. If the water comes from a well, there are usually minerals and metals dissolved in the water due to underground deposits. If the water comes from a community source, there may be chlorine, fluoride, and other compounds added to the water.

Water that comes from your tap should be safe to drink, but is probably not safe to soak in for very long without adding chemicals to the water. Initially when you fill the spa, the water probably did not have dangerous levels of bacteria, germs, or algae present. However, exposing that water to the air, sunlight, and to people, will cause drastic changes in the water. You also need to remember that since the tub contains only a small volume of water relative to the number of people using the tub, special attention needs to be paid to the duration of the filtering cycles and the chemistry of the water.

There are many items that are manageable in the water to make it safe to soak and we need to cover a few of those items.

WATER BALANCE

Water balance is a term used to describe the condition of the spa water when all the factors such as pH, total alkalinity, calcium hardness, total dissolved solids, copper, iron, and manganese along with temperature of the water are in their proper relationship with one another. A formula called Langler’s Index measures water balance. The ideal index reading is 0. A significant plus reading will cause scaling and cloudy water. A significant minus reading will cause etching, damage to heaters, and “red eye” in users.

pH

The term pH is a chemical symbol representing the potential of the hydrogen ion. pH measures relationship between the acidic and the caustic nature of the water in the tub. The pH scale reads from 0 to 14 with the midpoint of 7 being neutral (neither acidic or caustic). What some owners have trouble remembering is that this scale is logarithmic and not numerical. This means that when you move from the neutral 7 up to the reading of 8, you have not increased the caustic in the water one time, but multiple times.

TOTAL ALKALINITY

Total alkalinity is the measurement of the carbonate, bicarbonates, and certain other alkaline (caustic) chemicals in the water. The desired range is between 80 and 150 ppm. A low total alkalinity reading increases the sensitivity of pH changes in the water. This will allow the pH to “bounce” up and down. This is not good for the spa or the equipment. If the total alkalinity is high, the water will be cloudy and will use more sanitizer.

CALCIUM HARDNESS

Calcium hardness is the measure of the combined calcium ions present in the spa water. The ideal range is 175 to 275 PPM. Very low calcium hardness concentration will cause the water to be a pale clear green and in the case of a plastered spa the water will actually destroy the plaster. Very high calcium hardness concentration will cause cloudy water and a very high concentration will also cause the water to be a milky white.

PERFECT pH

We just finished talking about Total Alkalinity (TA) and Calcium Hardness (CH) and trying to give you a “snapshot” look at why they are important. A new product has been added within the last few years that will “lock” your pH into the desired range with one application after each refill of the tub. If your CH level is in the normal or less than optimum range, Perfect pH may be the easy way for you to maintain your pH. If you have a higher than desired CH level, adding Perfect pH may cloud the water and cause some of the calcium to participate out of suspension. You should not use Perfect pH if you have a plastered spa or high CH. If you use Perfect pH or similar products, you do not have to maintain the CH level of your spa water - one less chemical to be concerned with.

CHLORINE

Other than a complete drain and refill after each use (similar to what happens in jetted bathtubs), Chlorine is probably the oldest method of sanitizing water. It comes in all types, concentrations, and container sizes. The effective sanitizer is the hydrochlorous ion, which is part of the molecule of the different Chlorine sanitizers. Chlorine can be organic or inorganic and has varying strengths due to the blend of the mixture. Chlorine varies from a concentration of 5% such a NaOHCl2 (household bleach) to 99% C3N3O3Cl3 (Trichloro-S-Triazinetrione) which is Trichlor powder and is only used in very special applications. Not only does Chlorine vary in “strength” but also different compounds dissolve at different rates, have differing pH values, and most importantly, have different uses. Remember this about Chlorine – if mishandled it can be dangerous in whatever form you use it. Treat it with utmost care and follow the label instructions exactly!

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