It seems so simple. Fill the hot tub with water, turn it on, and, shortly thereafter, enjoy the soothing benefits of the hot tub.
But there’s more to hot tub use than that. Making sure the water is clean is key to preserving the benefits of the hot tub. The pH level of the water is critical to that cleanliness. By measuring the pH level of your hot tub frequently, you can ensure your hot tub remains safe for years of comfort.
What Should the pH Level Be?
The pH level indicates how acidic or alkaline something is. Measured on a scale of 0 to 14, a low pH (0-6) means the liquid is an acid; lemon juice has a pH of 2. A pH of 8 or higher indicates a base—ammonia has a pH of 12. Finally, a pH of 7 means it’s neutral—milk and water have a pH of 7.
The safe pH range for a hot tub is between 7.2 and 7.8—very slightly alkaline. At this pH, chlorine in the water will work effectively to keep the water clean, and, therefore, not harmful to you. Minerals in the water and sanitizers you add all affect the pH level; you should check it twice per week.
Harm from Low pH Levels
If the water in the hot tub is acidic, things can go wrong quickly. The acid will etch or corrode any metal it contacts. The heater is made of metal, as are many of the fittings. The hot tub walls may crack or delaminate. Sanitizers will be less effective.
The people using the hot tub will also notice itchy and dry skin, as well as irritated eyes. While the pH in a hot tub will rarely, if ever, get to dangerous levels, itchiness and irritation take away from the enjoyment of the hot tub. Low pH may also harm your bathing suits as the acid wears away the fabric.
Chlorine is crucial to keeping the water in a hot tub safe. Chorine works best in a slightly acid environment. Its effectiveness is at 97%, with a pH of 6. That level of acidity, however, would lead to the itchy skin and eye irritation noted previously.
It is worth noting that everything which goes into the water will affect the pH level, including the humans enjoying the hot tub. The pH of human skin is 5.5, which means we lower the pH of the hot tub each time we enjoy it.
Harm from High pH Levels
The hot tub also has problems from high pH levels. A pH of 7.9 or higher means the water is alkaline and can lead to cloudy water and scaling of the pool’s parts. The cloudy water is more an aesthetic harm than a danger to safety, but scaling is damage to the tub.
High pH values also affect the effectiveness of chlorine. A pH level of 8 means that chlorine is barely 20% effective and, when pH reaches 8.5, chlorine’s effectiveness is well under 10%. Chlorine, of course, is the most commonly used disinfectant for water.
Contaminated water can cause a variety of illnesses, largely because of bacteria. Most of these illnesses lead to gastrointestinal upsets, including nausea, stomach cramps, diarrhea, and vomiting. While these upsets will rarely be long-term (or fatal), they certainly can put a damper on your enjoyment of the hot tub.
Changing the pH to the Proper Range
Keeping the pH of your hot tub within the recommended range of 7.4-7.8 will ensure the hot tub is safe and enjoyable. The first step is, of course, checking the pH and alkalinity frequently. As a rule, check it twice per week.
If you notice cloudy water, you are probably noticing a symptom of high alkalinity and pH. You should test for alkalinity first. The level should be between 80 and 120 parts per million (ppm). Then, check the pH. If it is over 7.8, you will need to address it as well.
You should focus on the total alkalinity first. The chemicals most frequently used are sodium bisulfate or muriatic acid. Follow the instructions from your hot tub manufacturer and the product you use. Use a plastic bucket ¾ filled with water from the tub, and add the acid; the water should be in the bucket first. With the hot tub running, gradually add the contents of the bucket to the tub.
The water should circulate for 3-6 hours, and then check for alkalinity and pH again. The pH level follows alkalinity—check again if the alkalinity is in range, but the pH is not.
If the water has a low pH, you also need to measure alkalinity. The most commonly used chemical for raising alkalinity—sodium bicarbonate or baking soda—will not raise the pH by much. Sodium carbonate will affect both measurements.
Enjoy the Tub
pH levels outside the recommended range do not mean the hot tub is unsafe. You do need to address them, however, before things get worse.
Checking and treating the water is easy and, when this process becomes part of your household routine, it will ensure years of enjoyment of your hot tub.