Do you remember the first dip you had in your brand new hot tub? It brought you a blissful sense of calm and relaxation from the busyness of the day. But as time passes, you notice that your hot tub water is changing. It is no longer the inviting blue water once was. Instead, what you have is a hot tub of greenish, cloudy, and smelly water.


As you go through the manual to figure out what has happened to your outdoor spa, you suddenly find your head swimming with all sorts of terms and calculations. You feel overwhelmed, confused, and wondering what to do and where to begin to restore your spa.


Difference Between a Spa and a Swimming Pool


In addition to its size, one of the biggest difference between a spa and a swimming pool is the water temperature.

The water in an outdoor swimming usually ranges anywhere between 82 and 84 degrees Fahrenheit. Spas, on the other hand, have a water temperature between 102 and 104 degrees Fahrenheit. This is the reason why spas are sometimes referred to as hot tubs.

While the spa’s warm water temperatures help you relax as you soak in it, this also makes it a more favorable breeding ground for bacteria, fungi, and algae. Not only do these cause a wide range of skin infections. They are also what is causing the water of your outdoor spa to become cloudy and smelly over time.


Getting the Ideal Spa Water Chemistry


That said, it should not be surprising that your spa’s water chemistry should be different than that of your swimming pool.

What makes understanding spa water chemistry quite challenging is its size. The amount and kind of spa chemicals used should be high enough to make sure that the water in your outdoor spa is safe and clean. At the same time, it should be low enough that it doesn’t cause a nasty reaction on your skin and your family’s.

Several factors that affect your spa’s water chemistry and quality.




Of the different factors that affect your spa water chemistry, this is the most critical. It is also the most tricky.

Sanitizers are used disinfect and keep you’re the water in your spa clean and smelling fresh. Too little of this can quickly transform your spa into an ideal breeding ground for harmful microorganisms like bacteria, virus, mold, and algae. On the other hand, having too much sanitizer in your outdoor spa can cause you and your family to experience skin rashes and eye irritation. It can also make it very uncomfortable to breathe while you’re soaking in your spa.

There are several different kinds of spa sanitizers, but the most common ones are chlorine and bromine. The ideal reading for chlorine spa sanitizers is between 1.5 and 3.0 PPM while the average reading for bromine sanitizers is between 3.0 and 5.0 PPM. You can easily check this by using a spa water test kit you can get from your local pool supplies store.

When checking on your sanitizer reading, it’s important that you wait for a few minutes before testing your spa water. This way, you allow the sanitizer to mix in with your spa water, and you will get a more accurate reading.


Total alkalinity and pH levels


These two go hand-in-hand and directly affect each other. Alkalinity is essentially the amount of alkaline components in your spa water while its pH levels tell you how acidic or basic is your spa water. The higher the pH levels, the more alkaline your spa water.

Just like sanitizers, the best way to check this is by using pH test strips you can get from any pool supplies store. Your spa water should have a pH level between 7.2 and 7.8. If your spa water’s pH level is lower than this, that means that your spa water is too acidic, which can cause not only skin and eye irritations but also corrode your spa equipment more quickly. On the other hand, if your spa water’s pH level is too high, it means that there are too much alkaline products in it which can lead to your spa water becoming cloudy and making it harder for your spa filter to do its job.

The trick to making sure that your spa water’s pH level is within the acceptable range is to ensure that its total alkalinity level is anywhere between 80 and 120 PPM.


Calcium Hardness


Believe it or not, even your tap water can affect your spa water chemistry.

There are some regions in the country where the tap water is classified as what they call “hard water.” What this means is that the tap water contains high levels of minerals like calcium, magnesium, and iron. Using this type of tap water to fill your outdoor spa can cause the formation of scales on your spa’s surface and leave your spa water cloudy.

The ideal calcium reading for your spa water should be between 100 and 250PPM if your spa has an acrylic finish, and 250 and 450PPM for a plaster-finished spa.

If you see that your water’s calcium reading is higher than the ideal range, you can treat this by using a water softening agent.


Shock treatment


Shock treatment, otherwise called as “Super Chlorinating” is a process where you put a concentrated amount of chlorine or bromine into your spa water. This process breaks down all those unfilterable materials in your water like dirt, soap films, hair spray, lotion, oils, perspiration, and other organic matter so that they can be washed out. Otherwise, they would build up in your spa water and serve as a food source for bacteria and algae.

When giving your spa a shock treatment, it is important that your spa cover is open for at least 20 minutes. Otherwise, the fumes coming from the high concentration of chlorine or bromine tablets used during the shock treatment will discolor and corrode the underside of your spa cover.

These are the water chemistry basics that will help you maintain your spa. Just remember that unlike a swimming pool, the water in your outdoor spa doesn’t have any way of being pumped out. Make it a point to test your water regularly so that you can always enjoy soaking in its hot water to relax and unwind.