A canister filter system includes a base, a canister attachable to the base, and positioned inside the canister a filter element having filter media. A drain engages and forms a seal with the filter element in a closed position. In an open position, the drain allows fluid to be removed from the canister. Because the drain is engaged to and forms a seal with the filter element in the closed position, the drain cannot be closed unless a filter element is present inside the canister. This prevents accidental or intentional use of the filter system without a filter element in place.