I have a pool that came with the house. The sand filter has a mfg date of 2001. I don't know if the sand has ever been changed. However, it doesn't seem to filter efficiently. I have to run the filter 24/7 and even then the water does not clear up very fast. We've had a ton of rain the last few weeks and a lot of dirt in the pool. It's a little better after a back flush but the pressure never drops very much. Always seems to run around 18 ~ 20 psi. Think it's time to change the media? Thanks