How often should a heavily used commercial pool be drained?

How often you drain the pool depends on if the pool is indoors or outdoors. If the pool is indoors you may need to drain the pool if the TDS (total dissolved solids) get to high. This usually occurs if the TDS goes over 2000 ppm (parts per million) at that point you will notice the pool is cloudy and you cannot get it to clear up. If you should need to drain any pool you need to be aware of the water table in your area. At the bottom of every concrete pool there should be a hydrostatic relief valve that will allow the water under the pool to come into the pool relieving the pressure of the water under the pool and keep the pool from "floating" out of the ground. Before you drain the pool make sure that you have this valve, you will find it in the main drain in the deep end of the pool. DO NOT DRAIN THE POOL IF YOU DO NOT HAVE THIS VALVE AS IT CAN LEAD TO THE POOL POOPING OUT OF THE GROUND. If the pool is an outdoor pool when it rains it will be diluting the TDS and unless you have a very dry season or you live in dry area you will not have to drain the pool unless the surface of the pool needs to be cleaned. So draining the pool should be a very rare event.