Using these Drinkwell replacement foam filters is easy. First, turn off the fountain and unplug it. Then, remove the old filter from the fountain. Take one of the new filters from the 2 - pack and place it in the filter compartment of the fountain. Make sure it fits snugly. Plug the fountain back in and turn it on. For maintenance, it's important to replace the foam filter every 4 to 6 weeks to keep the water clean and the pump working well. If you notice the water flow slowing down or the water looking dirty before the replacement time, check the filter and replace it if necessary. When handling the filters, be gentle to avoid damaging them. Keep the filters in a dry place when not in use.