The first thing to do is turn off the filter from the system. Then, using an industrial vacuum cleaner, pump out sand from the filter tank. It is very important to control the full pumping of quartz sand from the filter. If you found lumps before the start of work, then most likely at the bottom you will encounter a “cemented” layer. This layer should never be broken. For its elimination, any sour solution is best suited. The most optimal is a weak solution of hydrochloric acid, but you can also use an automobile electrolyte.