Hot Tub Life Articles

What is the Hamilton Index ? - The Spa Guy Answers Questions

If you have a Hot Tub Spa question that you would like answered in an upcoming column, write to the Spa Guy
c/o Poolandspa.com, 672 Los Feliz Street; Las Vegas, NV 89110.

Dear Spa Guy,

One of my friends was talking to me the other night about his hot tub spa. He mentioned to me that he uses something called the "Hamilton Index" to maintain his water. He says the water is always clear, never smells, and it sounds like he uses a lot less chemicals than me. I did not want to sound ignorant, so I told him that I used it too! What the heck is this ? A brand of chemicals, a different test kit ? Please help !

R.S., Hobbs, New Mexico

Dear R.S.,

You know, when I agreed to write this column, I figured that most of the questions would be real easy, like "what is a pump ?". However I am beginning to see that I have to put a lot more thought into this than I planned !

I guess our readers are pretty knowledgeable about their spas, and you are certainly not "ignorant" to be unaware of the Hamilton Index. As a matter of fact, I bet many of our readers already use the Hamilton Index and don't even know it !

About 6 years ago, a California research group was looking for a way to improve the chemical sanitization of hot tub spa water. What they developed was named the Hamilton Index. It involves rethinking the ways people have always been taught to care for hot tub (or swimming pool) water chemistry.

Most of the information about spa water chemistry is given to spa dealers by the manufacturers of spa chemicals. This information is then taught to the spa owners. Obviously, the chemical manufacturers would like you to use the most chemicals possible ! With the Hamilton Index, you can actually use less chemicals and have better sanitized spa water.

The basic concept is this - for many years, the accepted chemical level reading for bromine was 2.0, pH was 7.4 and Alkalinity was 80. The Hamilton Index rethinks this accepted water chemistry. By analyzing the chemical reactions down to their molecular level, it actually turns out that these "old" accepted chemical levels are neither the most economical nor the best and easiest way to sanitize water.

Over the years, we at Poolandspa.com have seen that our customers have had a lot of trouble maintaining their pH and Alkalinty at the proper levels. If they boost the Alkalinity level, the pH goes up too much. When they add pH Minus to bring down the pH, the Alkalinity drops way down. They are caught in a perpetual "Catch-22" and usually end up getting very frustrated and just dump out and change the water. Proper use of the Hamilton Index specifically fights this problem of pH and Alkalinity bounce as well as cuts sanitizer use by up to 50 %.

According to the Hamilton Index, the Total Alkalinity level should be at least 100-120 instead of floating between 60 and 80. Remember, Alkalinity is different than pH and must be tested with either a test strip or a 5 part dropper bottle test kit. The benefits of running a higher Alkalinty are: less sanitizer is needed, the pH is much more stable, there is a reduced tendency for cloudy water and stale smell, makes maintaining other chemical levels easier and reduces the possibility of corrosion to metal spa parts.

The pH level should be kept between 7.6 and 8.2 instead of 7.4 to 7.6. The darker red color on most test kits is better than the middle pink/red color. The benefits of running a higher pH are: less sanitizer is needed, sanitizer is more stable, less skin irritation, less chemical smell, reduces corrosion of metal spa parts, reduces chance of algae, improves water clarity, and higher pH is automatically "locked in" when Alkalinity is at 100-120.

Your sanitizer level (bromine) should be 1.0 instead of 2.0. The lighter yellow color on most test kits is better than the middle yellow color. The benefits of this are: less sanitizer odor, less skin irritation, less inert chemical materials building up in the water, less water foaming, less sanitizer cost.

To start using the Hamilton Index, simply follow the our "E-Z Chemical Instructions" elsewhere on this Site. You will quickly find that maintaining your spa water chemistry becomes much easier, and something that you can do only once a week, rather than every few days. Feel free to call us if you have questions !