Spa Water Chemistry - Test and Balance



Testing your spa water regularly is the best way to really understand your water chemistry. It's always changing, your water chemistry - and usually very rapidly, when 3 or 4 adults jump into 500 gallons of water.

" Balanced spa water" means that your pH, Alkalinity and Calcium Hardness levels are correct. Each of these 3 can need adjustment, but in terms of stability - Hardness stays fairly stable, followed by Alkalinity. pH can have the quickest and widest swings in level, so pay especially close attention to your spa pH levels.


Testing Spa Water

Test strips are the most convenient way to test spa water, in part because anyone can use them - without much instruction. Even my 4 yr old grand daughter can test the hot tub! Just dip and swirl, then compare the colors - it's almost fun!

I use the AquaChek "Red" test strips, and check the water nearly every other day, or at least 3 times per week. These spa strips test for Bromine, pH, Alkalinity and Hardness - everything I need. digital-strip-tester

The AquaChek Digital Strip Reader is great for us older folks with tired eyes, or maybe for my color blind husband (who claims he isn't). Just dip the strip and then insert it into the strip reader. Colormetric scanner determines the reading, and displays an exact digital readout of your spa water chemistry levels.

When your spa water is not in balance, your sanitizer is unable to work effectively, and algae and bacteria may thrive. Besides helping to keep your spa water safe and sanitary, balanced water also protects your spa shell and equipment from scaling or corrosive water conditions.

Test your Spa! It's the only way to know what is too low and what is too high. Test your hot tub every time you use it, or at least once per week.

Balancing Spa Water

After testing the spa water, adjust your Calcium Hardness levels first. If your water is very soft (less than 150 ppm), you should add a small amount of hardness increaser (Calcium Chloride) to the hot tub. This buffers the water, and can help prevent spa foaming. Next, adjust your Alkalinity level, if it's outside of the range of 80-120 ppm. Add baking soda (Sodium Bicarbonate) to increase it, or use a pH decreaser chemical (an acid) to lower

With calicum hardness (Ca) and alkalinity (Alk) levels correct, move on to pH. When pH is too high (above 7.6), your sanitizer is very weak and sluggish. When the pH is too low (below 7.0), the bromine is very effective, but the water is dangerously close to acidic range. Over time, acidic water can be corrosive to the spa finish, spa filters and to your spa heater. Add pH increaser or pH decreaser, to keep your hot tub pH level in the 7.2-7.4 range.

Finally, with the spa water balanced, we can address the sanitizer level, and make any adjustments necessary, and shock the spa. It's always important to have balanced water first, before boosting bromine, or shocking the spa.

How Much Water is in my Hot Tub? To adjust your spa chemical balance carefully, you need to know how much water is in the spa, so that you can add the proper amount of spa balance chemicals. If you know the make and model, find the specifications sheet online for "water capacity". If you can't locate this information, you can calculate your spa's capacity by measuring your garden hose flow rate, and then monitoring how many minutes it takes to fill the spa. To do this, time how long it takes to fill a bucket of known size. If your hose takes 1 minute to fill a 2 gallon bucket, for instance - and it takes 150 minutes to fill the spa - you can deduce that your spa holds 300 gallons.

For hot tub adjustment chemicals, see our Hot Tub Chemicals section. When you maintain water balance in your spa, you won't need so many other chemicals. Not only that, but hot tub maintenance is reduced, and your spa components can last longer. Just from testing and balancing your spa water chemistry!

Carolyn Mosby
Hot Tub Works