In general, there are two time periods for when to change your spa water – either every 4 months or annually. The difference has to do with your spa sanitation regimen though how you use your hot tub may change both refill frequencies.
Changing Your Spa Water Every 4 Months
The most common frequency for spa water changes is every 4 months. This applies to most spa sanitation regimens including the use of dichlor, bromine tabs, biguanide, etc. With all of these chemical regimens, chemicals other than just chlorine, bromine, or biguanide are being added to your spa. A 4-month change is needed due to the gradual build-up of these chemicals as you add these chemicals on a weekly, or more frequent, basis. Eventually, usually around 4 months, the concentration of these chemicals in your spa is just too high causing foaming, reduction in the effectiveness of the actual sanitizer, and potential skin irritation.
Using Dichlor As Your Spa Sanitizer
Dichlor is the most common sanitizer used in spas. It is relatively inexpensive and effective at killing bacteria and other spa pathogens. It is a combination of chlorine and cyanuric acid (CYA) in an approximate 50 / 50 ratio.
Cyanuric acid is a two-edged sword in your spa. Its purpose is to extend the useful life of the chlorine in your spa. However, cyanuric acid also reduces the actual killing efficacy of the chlorine. As you add dichlor to your spa, you are also increasing the concentration of cyanuric acid. Generally, around 4 months you must drain your spa and add fresh water in order to remove the cyanuric acid and regain the full bacteria killing efficacy of chlorine.
Changing Your Spa Water Annually
An exception to the 4-month spa water change is spas using a salt system sanitation system. These spas have either sodium chloride or sodium bromide in the spa water. These are the “salts”. In fact, ordinary table salt is sodium chloride. The salt system converts these salts to either chlorine or bromine to be used as the actual sanitizer.
Salt System spas are not adding chemicals on a weekly basis to the spa. Generally, they only require the addition of salt once between each spa water change. I noted above that the reason for changing spa water every 4 months is the accumulation of chemicals in the spa water. Salt system spas do not have a build-up of chemicals though your own use of your spa will gradually add other chemicals that will need to be removed with a spa water change. The net result of not regularly adding chemicals in salt system spas is you can usually change your spa water annually.
Adjustments to a 4-Month or Annual Spa Water Change Cycle
I noted that other factors can alter these spa water change frequencies. These factors are collectively known as “bather load”. The higher the bather load, the more sanitizer is needed. Of course, the opposite is also true.
Bather load includes four factors. These are (1) How often is the spa used? (2) How many people use the spa? (3) How many hours per week is the spa used? and (4) How clean are the bathers? (Taking a shower before use is best but often not done.) As these factors increase so does the need for sanitizer. Hence higher bather load means the accumulation of chemicals in a spa is more rapid, causing a need to drain and refill your spa more often than usual.
When Should I Purge My Spa?
It’s important to note that in addition to changing spa water, you should purge your spa at least annually. Our Serum Total Cleanse is the best spa purge available. The active ingredient, benzalkonium chloride, and special salts, we use in Total Cleanse are not used in other spa purges.
Purging a spa removes the biofilm that develops and grows in the plumbing of almost all spas. In addition to being gross, these biofilms put an added load on the spa sanitizer, hence you want to get them out.
What Does It Cost to Change Your Spa Water?
I occasionally hear concerns expressed about the cost to replace the water in a hot tub. But when you do the math, the expense is minimal and certainly not sufficient to suggest delaying changing the water in your spa on a regular basis. Here is an example.
The typical hot tub contains around 400 gallons of water. The most expensive water in the US is in San Diego at nearly $1.82 per gallon. This includes both the actual cost of the water and discharge / sewer fees. Hence, the cost to replace the water in a 400-gallon spa in San Diego is a bit over $7.00 and that is the most expensive location in the nation. Your costs is very likely quite a bit lower than this.
Thanks for reading,
