How often should I replace the cartridge filter and/or grids?

The first indicator of a cartridge needing to be replaced could be severe bloating of the pleats (folds of the cartridge) or inability to proper cleanse with routine maintenance.

D.E. grids should be replaced if debris appears to be bypassing the filter and returning directly back to the pool, as this will typically indicate the cloth-like material that covers the grids has been torn.

Otherwise, grid replacement should take place if physical inspection shows any rips, tears, or structural breakage of the grid's framework.

You should always verify proper operating pressure on the filter as a quick indicator of possible filtration issues.