Hot Tub Water Chemistry 101
The water chemistry of your hot tub is the most important factor in determining its lifespan. It is imperative that you learn the basics of water chemistry to ensure safe bathing conditions and keep the components of the hot tub from deteriorating prematurely.
The basics of hot tub water chemistry are universal: pH, alkalinity and sanitizer. The concepts and monitoring of both pH and alkalinity are the same/similar regardless of the sanitizer used. As noted in the images above, there are 3 main types of sanitizers used today: Nature 2, chlorine and bromine.
At a later date we will dive into the secondary products that buttress your hot tub chemistry. But for now we will focus on the the primary "big three:" pH, alkalinity and sanitizer.
pH and Alkalinity
pH and alkalinity tend to work in tandem assuring that your sanitizer is effective as possible. If in the desired range, pH will allow your sanitizer to work to its maximum efficiency. Most pH testers will measure on a scale from 6.4 to 8.6. For pH in most cases, a range of 7.2 to 7.8 is preferred. However you should check with the label on the specific sanitizer you are using for the proper pH range.
pH imbalance can lead to a loss of sanitizer effectiveness. Additionally, pH and/or alkalinity that is habitually low can lead to scaling of your spa surface. Scale is generally defined as metals that have deposited on the spa shell. Scale is relatively easy to alleviate but shouldn't occur on a regular basis, as this denotes your spa chemistry is out of alignment. If the pH is habitually high it can lead to corrosion of your jets and heating element. Virtually all spa warranties do not cover this and can be costly to remedy.
Alkalinity acts as a buffer for your pH: Imbalancers (tap water, usage, etc) that try to push your pH out of line must first eat away at your alkalinity. Keeping your alkalinity in line allows your pH to stay in line longer, which in turn allows your sanitizer to stay in line as long as possible, keeping bacterial and algae levels as low as possible. The adverse effects of alkalinity imbalance are similar to pH imbalance.
As noted above Nature 2, chlorine and bromine tend to be the most common sanitizers on the market. All three have clear pros and cons and Prestige Pools and Spas does not universally recommend one type of sanitizer of the others. Instead, we prefer to see what are the wants and needs of the user and cross reference that with the pros and cons of the sanitizer before we make a recommendation.
Nature 2 Mineral Cartridge
The most popular spa sanitizer in our market today, Nature 2 "works by automatically dissolving trace amounts of mineral elements into the water. Those elements act as a sanitizer to destroy bacteria and viruses." This is a low-chlorine alternative, with the active mineral being silver.
We refer to the Nature 2 mineral cartridge as the "passive sanitizer," as it works well with keeping the water clean and free of bacteria and algae while the water is between uses. However, once the tub is used extra impurities such as sweat, lotions, makeup, dead skin cells, etc. we need to be countered. When using Nature 2 you are required to add Spa Shock (Potassium Peroxymonopursulfate, or MPS), which acts as an "active sanitizer." Spa shock is a non-chlorine based energizer that oxidizes the aforementioned impurities and should be added regularly after each use.
Chlorine (packaged as Sani Spa here at Prestige Pools and Spas) will be necessary with Nature 2. When the spa is initially filled and balanced a small dosage of chlorine should be added to activate the Nature 2 cartridge. In times of heavy bather loads you may need to add a small amount on a weekly basis
Pros: Nature 2 is the softest on your skin, has the least amount of "chemical" odor and uses the least amount of harsh chemicals.
Cons: It requires the most amount of upkeep, as Spa Shock must be added regularly to keep your water clean and clear and healthy. It can also be the most expensive of the three most common sanitizer options.
Chlorine (Sani Spa)
Chlorine is one of the oldest and most common sanitizers on the market. Its known for being cheap and easy- It tends to not need a shock in most cases (save for perpetual heavy usage) so the number of components is limited. If you don't want to spend a lot of time and money dealing with your water chemistry (other than what you are required) chlorine is typically the way to go, as its a no-nonsense sanitizer that gets straight to the point.
The most important factor when dealing with chlorine as a sanitizer is to make sure you only use granulated chlorine: Tablets will emit a gas and as hot tub covers tend to remain closed when not in use the gas can build up. This is a potential health hazard. Granulated chlorine is quick dissolve and emits a fraction of the gas tablets produce.
Pros: Cheap and easy. Less components overall to purchase and keep track of.
Cons: Emits the most odor, harshest of all the sanitizers on your skin.
Possibly the least common sanitizer but with the most loyal of following, bromine is easiest explained by calling it the hybrid of the two aforementioned sanitizers. It has many of the same pros and cons of each, just to a lessor extent.
Bromine comes in tablet form and utilizes a floater. Though approx. 30% chlorine in its make-up, it is safe and won't emit a noxious gas. It also requires Spa Shock to help oxidize the build up of particulate matter from usage.
The key to bromine is that you must first de-chlorinate your water before the addition of your bromine tablets. The only acceptable form of bromine for your water is in tablet form. Often, users will use the granulated version of bromine (sodium bromide) instead of the bromchloro chemical compound that makes up the active ingredient in bromine tabs. Sodium bromide is not an adequate sanitizer on its own (unless used in conjunction with a specially modified "salt system" for your hot tub).
Pros: Less odor than chlorine, softer on your skin than chlorine, cheaper than Nature 2.
Cons: Utilizes a floater, more expensive than chlorine, not as soft as Nature 2.
Need Further Assistance?
Let us know if we can help in any way. We offer free chemical analysis in-store or can answer questions via email at email@example.com. Or you're welcome to call us at 314.821.6660.
Happy hot tubbing and good luck moving forward,