A wound therapy system includes a wound dressing fluidly connected to a fluid canister. The fluid canister is attached to a canister receiving attachment of a housing structure. A pump is fluidly coupled to the canister and is configured to draw a negative pressure within an interior of the canister. A controller of the wound therapy system is configured to operate the pump to apply a vacuum to the interior of the canister and to obtain one or more measurements representative of at least one or a flow rate of air that is exhausted from the canister interior, a pressure within the canister interior and pump ripple. The controller is configured to estimate the volume of the canister based on the comparison of the measured parameters against model data stored by the controller that is representative of the operation of the therapy system with canisters of varying volumes.