Health Considerations for Hot Tub Owners

Few would deny the health benefits of relaxing in your very own hot tub. What some owners may not realize, however, is that when improperly cared for hot tubs can pose some significant dangers.

The warm water of a hot tub, when combined with organic matter, can create a breeding ground for potentially harmful bacteria. Among the more common risks are Legionella pneumophila, the cause of both Legionnaire’s disease and Pontiac fever, and Pseudomonas aeruginosa which can cause red rashes and even abscesses. There is also some evidence to suggest that the Herpes virus may also survive in hot tub water. Algae may proliferate, causing the water to turn cloudy or smell unpleasant.

Properly cared for, your hot tub should continue to bring pleasure for years into the future. On the other hand, the seeming luxury of a home hot tub can quickly turn sour if the correct routine is not maintained. In this guide we will look in depth at how best to keep your hot tub water fresh and hygienic, and thus how to avoid the potential risks that an uncared-for spa may represent…

The Four Stage Process

Managing the chemistry of your hot tub water can be a complex process for the uninitiated. Attempting to decipher the many chemicals and their uses can frustrate even the most patient of readers. For the purposes of this guide therefore, maintaining your hot tub water for optimal health can be thought of in four stages.

These are:

  1. Water Testing
  2. Sanitation
  3. Oxidation
  4. Filtration

We’ll look at each of these topics in turn, in order to keep the information presented as orderly and logical as possible.

#1. Water Testing

Hot-tub-water-testingPossibly the simplest stage of all is testing the basic chemistry of the water in your hot tub. Incorrect water chemistry can lead to a range of problems; health-wise poor chemistry can cause skin and eye irritations, as well as making the other steps of the process less effective. Supplementary to your personal health, incorrect water balance can also shorten the lifespan of your hot tub itself.

The easiest way to test your hot tub water is to use test strips as sold by specialist retailers. These strips allow us to test for the following elements:

  • pH – pH is a measure of how acidic the water in your hot tub is. When this is wrong, skin and eye irritation can follow. Just as importantly, the sanitizer which is used to clean the water works less effectively. Cloudy water may also be observed. The optimal pH for a hot tub is as neutral as possible. A pH reading of between 7.2 and 7.8 is ideal. Fortunately it is simple to correct pH using chemicals; one increases the pH while the other reduces it.
  • Total Alkalinity – Total alkalinity affects how easily we can change the pH. The optimal range is 80-120 PPM (part per million). Once again, there are chemicals available to help increase or decrease the total alkalinity.
  • Calcium Hardness – Calcium hardness is essentially a measure of how much calcium is in your water. The health impacts here are only indirect, in that hard water can lead to less effective filtration. It is included here for completeness, and once again can be controlled through the use of chemicals. The ideal level for hot tubs is around 100-200mg/l.

With these checks complete, and the levels corrected, we can then continue to the next stage of our program; sanitization.

#2. Sanitization

hot tub water sanitization

The first stage of our regimen really just set the scene for this stage; in essence we were primarily focused on making sure that the chemistry was right for sanitization. In this second stage we actually go ahead and “clean” the water of microbes, algae and other unwanted potentially disease-causing agents.

There are a number of different alternatives here to sanitize your water. Here are some of the more popular options:

  • Chlorine – One of the best-known and most reliable sanitizers is chlorine. This chemical is supplied in granular form, and great care should be taken to add the right amount based on our previous readings. The granules quickly dissolve in the warm spa water, particularly if you leave the water jets on while dosing. The downside to chlorine is that it can cause irritation, especially if it gets in the eyes, or for those with more sensitive skin.
  • Ozone – Less an alternative, and more a supplement, ozone may be pumped into the water. The ions released then help to sanitize the water. Note that ozone is generally used alongside chlorine, but that when using ozone sanitization less chlorine is required. This means fewer irritations for users.
  • Salt Water – In a similar vein, salt granules may be used as a sanitizer, which reduces the volume of chlorine necessary.

While none of the above methods is necessarily “better” than the other, an increasing number of users opt for the second or third options, which minimize the harsh side effects of traditional chemical use.

The key, irrespective of the option chosen, is to rigidly follow the guidance provided by the manufacturer, in order to ensure the effective removal of microbes with the minimum of irritation for you and your family.

In many ways this sanitization process can be thought of as ongoing maintenance. Water should be checked every week or so followed by sanitization.

However despite this process, it is likely that some micro-organisms still survive. This is because of the relatively low levels of chemicals used in standard sanitization. To kill everything we move on to stage three – oxidation.

#3. Oxidation

hot tub Oxidation

Oxidation is also known as “shocking” your hot tub. It can be thought of as a more severe version of sanitization, in essence using a higher volume of chemicals. This is done less often as sanitization handles the majority of micro-organisms, and using a spa after oxidation can be uncomfortable.

Experts recommend shocking your system after a period of non-use, after heavy use (lots of guests over the weekend) or every four weeks. Once again, be sure to use approved chemicals designed to work with your hot tub, and follow the dosing instructions carefully.

While there are a range of shocking liquids available for hot tubs, the vast majority are chlorine-containing. They are added to the tub after use (not before) and left to do their magic. Such a dosing will essentially damage any microbes floating in or on the water. These, together with dead skin cells and cosmetics like suntan lotions, can then be removed from the water by your filter.

#4. Filtration

hot tub Filtration

Filtration is the final stage in this cycle, whereby the water is physically strained through a mesh. This filter slowly becomes clogged with matter, and so needs to be cleaned to remain efficient.

Most manufacturers recommend that filters should be cleaned every two weeks by washing them vigorously with a hose to remove any physical detritus. Less frequently, typically every 3-4 months, the filter should also be soaked overnight in liquid filter cleaner. The following day the filter can again be hosed clean before being reinserted into the hot tub.

Once again, most hot tubs come complete with manufacturer recommendations on how often to clean your filter.


As you can see, maintaining the water quality of your hot tub to prevent bacterial or viral infection is not without its complications. In many ways each hot tub owner will need to experiment with their own cocktail of chemicals in order to keep their water hygienic. Armed with this guide, however, and paying attention to the guidance of your local pool chemicals supplier, you should be well on your way to enjoying all the benefits of your hot tub, without any of the potential risks.