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The operation pressure of your filtration system will increase when the filters are dirty because the pumps are having a harder time pushing water through the filters. This higher pressure on your gauges is a great indicator of when its time to clean the filters. There are cases when the pressure won't increase even though the filter is dirty, such as if there is a hole in the filter that water can easily flow through. However, in most cases, high pressure is a good sign that your filter needs cleaning. Unless your pool gets very dirty, very often, this should only occur once or twice a year. Locate the main electrical breaker for the pool filter system and turn it to the off position. Then locate the water supply disconnect and turn it to the off position as well. Turning these off before you remove your filter will ensure that water will drain from the filter compartment and that there will be no risk of shock while you are cleaning out your filter. Once the water is turned off, you can release the system pressure by turning the pressure valve. The valve is usually located on top of the filter compartment or near to it. Releasing this valve will allow the water to drain from the filter compartment before you take the lid off. You will know that you have successfully released the valve when you hear pressurized air coming out of it. In most cases, you will turn the valve counterclockwise until it won't move any more to release the pressure in the system. The top of the filter compartment is usually held on with a clamp. Use a wrench or pliers to open up the clamp handle, which will allow the top of the compartment to be removed. Once the top is off, you can grab the filter and pull it straight up and out. There are a variety of types of clamps that may be used on your filtration system. Follow the instructions that came with the system to properly detach the lid of the filter compartment if it is unclear to you. Once the filter is out of the filtration system, look over the entire filter for holes and tears. Even small rips can let water flow through without removing dirt and debris. If the filter is damaged, it should be thrown away and replaced, instead of cleaned. It's best to inspect the filter right away after removing it so that you don't waste time cleaning a filter that should just be thrown away.
Remove the filter when the pressure is 7-10 lbs above normal. Turn off the pool pump and water supply to the system. Release the air relief valve to depressurize the filter system. Open up the filter compartment and pull the filter out. Inspect the filter for damage.