Total Alkalinity is the measure of all of the alkaline substances that can be found in your pool or spa.
Your main focus when dealing with Total Alkalinity is to measure your calcium carbonate, keeping your calcium carbonate in a safe range will help with the up keep of your pool and much more. Your Total Alkalinity should be kept between 80 parts per million and 120 parts per million. When your Total Alkalinity is in this range it will prevent rapid pH changes in your pool or spa as well. It really helps to stabilize the pH.
If your Total Alkalinity is low there are many things that this could do to your pool or spa. With it being low, it can corrode metal parts that are in the pool or spa, for example your steps, hand rails, pumps, etc. it can also stain the pools walls and floors, and make the water green. On top of all that it will cause your eyes to burn and can cause your pH to bounce seemingly at random. If your Total Alkalinity is too high it really makes it difficult to adjust the pH levels in the pool or spa. With the Total Alkalinity being too high it can also make your water cloudy and cause the chlorine to lose its effectiveness as a disinfectant. This could also cause your filter and heating elements to get clogged up. So keep in mind that it is very important to keep your Total Alkalinity in the correct range and it will make it a lot easier for you to be able to keep up with the up keep of your pool or spa.