Guest Column - April 2008
Find a printable version here

Spas: Hot Water Basics

By Terry Arko

any pros who begin servicing hot tubs often do so with a misperception that caring for a small spa or hot tub will be easier and involve less chemical use and time than a swimming pool. Those who have cared for spas and hot tubs know that nothing is further from the truth.

In fact a spa is much more than just a tiny swimming pool. There are many differences between a pool and spa, and these differences call for a different and more strategic plan for care:

  • Most pools have a maximum temperature of 80 degrees; for spas it's 92 to 104 degrees.
  • A higher evaporation rate leads to more scale and increased calcium levels.
  • Air jets and blowers cause quicker chemical reduction.
  • The smaller body of water means a greater affect on pH, total alkalinity, calcium hardness and TDS from added chemicals.
  • The bather load ratio is far different.
Balance your water

Balanced water is critical in a spa. There are two main adjustments to be made when dealing with spa water:

Total Alkalinity: This creates a buffer in your water so that it can resist any acids that may be added to the water. This is the first and most important adjustment to be made. Total alkalinity acts as a control to the pH. The pH cannot be properly adjusted if the total alkalinity is out of the suggested ranges. The recommended total alkalinity range in spas is 80 to 120 ppm.

pH: This is a measurement of the acids or bases in the water. A low pH indicates the water is primarily acidic. A high pH means that the water is more base or alkaline.

A good tool for adjusting and holding pH and alkalinity in place between drainings is to use a product that holds the pH steady by boosting the total alkalinity. The technology raises the alkalinity by adding a soft form of calcium to the water. The result is the pH gets locked in and can't be easily affected by acids.

Common Hot Water Problems

CLOUDY WATER: Lack of sanitizer, shocking and clarifier. Check filter and clean or replace cartridge. Check water balance, shock and clarify water proactively on a weekly basis.

COLORED WATER: Metals, i.e., copper, iron. Check water balance. Low or high pH can cause copper to precipitate. Oxidation can cause iron to drop out. Check water balance use stain and scale prevention products.

FOAMING: Caused by soft water or by high dirt and oils in water. Increase water hardness with calcium chloride. Use a clarifier that flocs organics and oils or an enzyme. De-foamers help temporarily, but many are straight silicone oil and exacerbate the problem in the long run.

CHEMICAL ODORS AND EYE AND SKIN IRRITATION: Need for shock, water balance, make sure cover is left off when shocking. Check TDS and drain water if needed.

SKIN RASHES: Source water bacteria pseudomonas. Allergy to chemicals chlorine or bromine. Improper water balance, lack of sanitizer or water in need of draining.

BIO-FILMS: If spa and hot tubs are not maintained and sanitized properly, a bacteria-containing slime can form on filters and in plumbing. This bio-film can contain disease-causing bacteria. Clean filter cartridges monthly with a good filter cleaner follow by rinsing thoroughly with a high-pressure nozzle to break up and prevent the formation of bio-film.