Hot Tub Water Chemistry

APSP recommends using one of its member companies to provide support for maintaining, using and caring for your hot tub. If you want to maintain it yourself, we have developed 7 steps to keeping your water clear and healthy. ALWAYS make sure your filtration pump is working and wait 30 minutes before adding different chemicals.

  1. Testing Water Hardness
    • The hardness of your warder is determined by the calcium level. Too much calcium could cause scaling and excessive foaming. The ideal calcium levels should be between 200-400 parts per million.
        1. Fill your hot tub or spa
        2. Use a test strip while the water is still cool
        3. Add a product to raise the calcium level to cool water
        4. Wait 2-3 days before retesting
        5. If you have added too much calcium increaser, drain 6-12 inches of water, refill and retest
        6. For water with too much calcium, run it through a water softener or keep water and alkalinity levels in balance and use a mineral protection agent
  2. Balance Your Water
    • Balancing your water means keeping your pH level between 7.2 and 7.8 ppm and your alkalinity between 80 to 120 ppm. Water that is too acidic could corrode your components and irritate your skin. A pH level that is too high could cause scaling and damage to your hot tub's shell.
      • Use a test strip to measure your pH and alkalinity levels
      • Always correct alkalinity first by running the pump on high
        • To raise alkalinity, use a product that will raise the alkalinity and follow the instructions
        • If the alkalinity is in range and the pH needs to be raised, add half an ounce at a time, wait 30 minutes and test again, repeat as necessary
        • To lower alkalinity without lowering the pH, add as much product as necessary
        • If the pH still needs to be lowered, add half an ounce at a time, wait 30 minutes and test again, repeat as necessary
        • If your have high alkalinity and a pH below 7.0, drain 6 to 12 inches of water, refill and retest
  3. Choosing & Using A Sanitizer
    • Chlorine - A fast-acting for correcting aggressive water problems. It is recommended to keep it on hand to use to shock the water if needed. Chlorine is available as Trichlor, which is slow dissolving recommended for pools, and Dichlor, which is quick dissolving and recommended for hot tubs. Avoid using chlorine for pools as it can cause many problems, including invalidating your warranty.
    • Bromine - Commonly used in hot tubs because it doesn't evaporate as fast as chlorine. It can be added to water using two different methods:
      • Tablets are the easiest method of adding bromine to your water and require the use of a floating dispenser which should be removed when you use your hot tub and replaced when you exit. Some models have an independent pump and hidden skimmer basket to hold bromine tablets which will sanitize the water more frequently and doesn't require removal.
      • Sodium bromide is a two-step process because it needs to be activated with an oxidizer like chlorine or a non-chlorine shock. It requires a little more effort and is a learned process.
    • Mineral cartridges - Can be installed in the filter or used in a floating dispenser. Most cartridges last up to 3 months and we recommended they are used in conjunction with chlorine, bromine or a non-chloring shock.
    • Ozone - Powerful oxidizer that keeps water free of bacteria, mold, spores and viruses. Many hot tub models come with an ozonator that feeds ozone gas into the water and produces "off gasses." Ozonators should not be used on indoor spas unless they are properly vented. They are designed to be used in conjunction with another sanitizer.
  4. Prevent Scaling & Staining
    • Many local water areas contain high levels of iron and/or copper which can stain your spa shell, damage your heater, discolor water and require more sanitizer. Add a stain & scale agent every week as a preventative measure. Test your water to determine the right amount of agent."
  5. Keeping Your Water Clear
    • Hot water can cause bacteria to form and cloud or discolor your water. Add a clarifier when you first fill your hot tub to prevent cloudy or discolored water. There are two types of clarifier:
      • Natural enzyme - breaks down the organics and contaminants in the water, minimizes scum line and oil slicks without creating more work for your filter or limit the water flow of your jets without affecting water chemistry
      • Synthetic coagulant - bond many small particles into a larger mass which can be cleaned by the filter, while cheaper than natural enzymes, synthetic coagulants can affect your water chemistry.
  6. Clean & Replace Your Filter
  7. Keep Your Hot Tub Covered
    • Covers help keep your water clean, prevent evaporation and maintain a safe water environment.

Common Questions on Water

Why do I need to correct my pH/Alkalinity constantly?
Almost everything can cause the pH level to change; Example: spa usage raises the pH level whereas adding chlorine lowers it. Alkalinity can also change when you add water.

Why is the pH level higher in my spa than in my pool, or when I test it from source water?
Warm water maintains a naturally higher pH level.

Is it better to have the pH read on the low or high side of 7.2 to 7.8?
Chlorine prefers a lower pH level (7.2 to 7.5) where bromine works equally well throughout the entire range of 7.2 to 7.8.

What is the benefit of using Potassium Monopersulfate?
This non-chlorine shock agent reduces the use of sanitizers by doing some of the work of chlorine and bromine by oxidizing contaminants and requiring the chlorine or bromine to simply do the sanitizing.

What is Scaling in the Water?
Scaling is a precipitation (like barnacles) that forms on the internal spa components along with the spa shell when they are in contact with water where there is a too high level of Calcium, pH, alkalinity, and/or mineral content, or an excessively high water temperature.

Will it hurt my spa or my water chemistry if I add too much of a mineral agent?
The overuse of most mineral agents will not affect your water chemistry or hurt your spa but it is recommended to check with the manufacturer of the product you are using.

How Often Should I Change My Water?
The common answer voiced by all is every 90 days but it actually depends on the amount of chemicals you have added to your water. If you use your spa more often you may need to check the total dissolved solids level. If your water is oversaturated your chemicals become ineffective.

What Causes the Foam in Spa Water?
Common causes of foaming are laundry soap residue on bathing suits and cleaning solution on filter cartridges that have not been thoroughly rinsed, along with deodorant, body lotions, hair products, waiting too long to change your water, high pHlevels or poorly formulated chemicals.

What causes milky water and how do I correct it?
Untreated cloudy water can become milky water. Adding ph+ to a spa with very low pH level can cause a temporary chemical reaction that creates cloudy water. Adding a Natural Enzyme clarifier and putting in a new filter will help.

When I haven’t used my spa or jetted bathtub over a period of time I sometimes get a foul order when I first activate the jets. How can I rid myself of this problem?
This is a very common problem especially with jetted bathtubs since they do not have a filter system and the water in the lines often remains stagnant breeding bacteria. It is also a problem with hot tubs that have multiple pumps and jets where they are all not required to activate once or twice a day (often referred to as a clean out system). To rid yourself of this problem you can use a product often referred to as a jet-line cleaner.

Do Chemical Products have a shelf life?
Most chemicals do not have a shelf life as long as they are kept in a temperature controlled, dry environment. Liquid chemical products that freeze-up and granular products that are hardened should be disposed of.

Is it beneficial to purchase from a US Supplier?
Yes, primarily because many products are sensitive to temperature and humidity there is a possibility that ocean based shipments could have experienced extreme temperature conditions in their transit causing damage that may even not be noticeable to the US vendor.