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According to Wikipedia, Total Dissolved Solids (TDS) can be defined as, “a measure of the combined content of all inorganic and organic substances contained in a liquid in molecular, ionized or micro-granular (colloidal sol) suspended form. The most common chemical constituents are calcium, phosphates, nitrates, sodium, potassium and chloride, which are found in nutrient runoff, general stormwater runoff and runoff from snowy climates where road de-icing salts are applied.” Depending on who you talk to in the swimming pool industry, TDS can be a measurement used to determine if you should change the water in your swimming pool. Is this a good determining factor? Well, according to us NO and here’s why:

First of foremost, we don’t like to use it as a determining factor because of how swimming pool water gets tested. Typically, a small amount of water is placed into a cup  and an Electric Conductivity Meter is used to determine the TDS levels in the swimming pool. The water can also be placed directly into the meter (picture shown above). This type of test can be challenging to get accurate results because it is only used in chlorinated swimming pools. To drive this point home we conducted a test and took the same swimming pool water into a pool store. In one of the samples of water we added a small amount of salt to the water and the results were quite intriguing. Both water samples came out the same except for the measurement of TDS. Because salt is highly electroconductive one of the samples pinged the meter and even though it was the same water, the technician recommended that the pool be drained due to high TDS levels. Does this make the test accurate or should this be a determining factor when a swimming pool owner decides to drain or recycle their swimming pool water? We don’t think so and this is why anyone who owns a swimming pool should be educated on water chemistry.

The true determining factor on whether or not you should drain or recycle your swimming pool should be increasing calcium or cyanuric acid (CYA) levels in the swimming pool. In certain parts of the country as water evaporates the calcium levels in the pool rise because of the fill water. When calcium levels rise it can be a nightmare because it stains the water tile line, the liner of the swimming pool, it destroys equipment and ruins water features. another reason as to why a swimming pool owner should change out their water is rising CYA levels. As CYA climbs above 100ppm (typically if you use chlorine tabs) it prevents chlorine from working effectively. When this happens, it’s easier for algae to grow in the pool.

Whether it’s high TDS, calcium or CYA levels you must look at all determining factors before choosing to change out your water. If you live in the Southwest U.S. we recommend changing out your water every 2 years. The best part about all of this is our mobile filtration system can remove all these contaminants from the swimming pool which gives swimming pool owners an option to conserve 85% of the water in the swimming pool and in turn gives them the best possible water in their swimming pool. If you’re curious as to how we recycle swimming pool water you can watch this short VIDEO.