PH level in a hot tub is more important than you might think. I’ve come across many customers over the years that don’t ever test their PH level. They feel that if the water is clear, that’s all that matters. They add chlorine or bromine weekly and as long as the water looks good they don’t test anything else. I am going to give a few examples that will show why this is not a good practice to get into.
PH is measured in a range from 0-14. This is the same PH scale you learned in science class in school. 0 is the low end of the scale and in water is extremely corrosive. 14 is the high end of the scale and is considered alkaline. 7 on this scale in the middle and considered neutral. The safest range to keep your hot tubs water in would be from 7.4 to 7.8. If the water in your tub falls out of this range to the low side, the water will become acidic and corrosive. This will not be good for your hot tub or your body. In the tub acidic water will corrode or etch any metal it comes in contact with. The heater in a hot tub is made of metal and won’t take long to corrode and stop working in acidic water. Now I’m not a doctor, but sitting in acid can’t be good for your body either.
If the water in your hot tub heads above the recommended range, it will also cause several problems. Some of these will be scale and cloudy water. Scale in hot tubs and swimming pools is caused by high PH which allows minerals in the water to fall out of suspension onto tub surfaces. This will leave behind a chalky or gritty residue on the tub’s surface and inside the plumbing lines that will break down any plastic or rubber components in the hot tub. The other result is cloudy water. When the minerals in the waterfall are out of suspension they “show themselves” in the water.
Several factors can cause PH to change in the water. The two most popular reasons are filled water and the sanitizer being used. If you fill with hard water or well water, your PH will rise dramatically. Most well water I have tested comes out of the ground at a PH level of 8.6 or greater. This may differ in other parts of the country or world. The best way to know what is being added to your spa is to test the water coming out of the fill hose. This will tell you whether you are going to change the PH level in your spa by adding fresh water. The sanitizer used in the tub will also affect the PH level. If you are using dichlor (stabilized granular chlorine) it has a PH factor of 6-7. This won’t change the level that much. Calcium hypochlorite (unstabilized granular chlorine) has a PH factor of 12-13. This will raise the PH level in your spa greatly. Bromine has a PH factor of 4-5 but less bromine is used in hot water than chlorine. Also, remember that chlorine is not an effective sanitizer in water that has a high PH.
Just because a hot tub looks clean and has clear water don’t assume everything in the water is fine. A hot tub with water in it that measures at a 6.0 PH level will be crystal clear. The reason being, nothing can grow in acid. The heater and other hot tub equipment will begin to corrode away and your eyes and skin will burn, but that water will look great. Do yourself a favor and test your spa water weekly for sanitizer and PH. It will save you time, money, and possibly your health. If you don’t have a proper test kit, get one. “Drop” test kits are more accurate than test strips. You can also take a water sample to a qualified pool or spa professional for testing. They will be able to tell you what is in your water and how to adjust it. But be careful don’t get oversold by a salesperson.