It is recommended that the sand in your filter is changed every five years. It is possible to run a filter for longer, but its efficiency will decrease rapidly.
Filter sand has been ground to a size of 0.3 to 0.5mm and is very rough when new. The roughness of the grains is what helps the sand to be efficient at removing the particles of dirt in the water, and return a clear, sparkling water to the pool. Over a long period of time the roughness becomes smoothed out, and the efficiency of the filter consequently diminishes. The system then has to run more frequently to achieve the same task. Your chemical costs may increase as you will have to use more sanitizer. After five years the sand becomes smooth and broken down, this traps the dirt deep down, making backwashing more and more difficult. The result is shorter filter cycles which requires more frequent backwashing. The consequence of this is shorter filter cycles and increased backwashing.
You need to start by removing the old sand. Start by opening the filter. If your filter is the type with a top mounted multiport valve, then you will have to disconnect the pipe work connected to the valve. Often this means cutting the pipe as threaded unions are often not included. This may be a good time to install unions to make servicing easier next time. Filters that have a plug at the bottom are the easiest to remove sand from. Removing the plug will enable the sand to flow out and you can then use a hose to wash the remaining sand from the tank. If your filter does not have this drain plug, then you need to remove the sand by scooping it out from the top. Before you do this undo the drain plug to release any water. Remove the sand using a cup being very careful not to damage the laterals connected to the stand pipe. Filters which have the multiport valve as a side mount have a lid on the top which can be removed by unscrewing. It is now possible to clean out the old sand as described above. Once all the sand has been removed you will should clean and examine the laterals thoroughly. Most laterals simply unscrew easily, and are easily removed from the tank. Check the laterals for any signs of breakage, and replace them if necessary. The laterals should be checked for any damage, cracks or splits, and replaced if necessary.
Finally, rinse out the tank and re-install the clean laterals. Now replace the sand. After each bag of sand has been emptied make sure the bed is level before adding the next. Finally, reassemble the pipework.
