A channel device for transporting gas and liquid between a control unit and a scope accessory, the channel device comprising a wash line and a gas line, the wash line comprising: a wash line gas channel; a wash container; and a wash line wash channel, the wash line gas channel being configured to receive a gas from a wash line gas output of the control unit, wherein the wash line wash channel is configured to attach to a wash line input of the scope accessory, the gas line comprising a gas line channel configured to receive a gas from a gas line gas output of the control unit, and to transport the received gas to the scope accessory, wherein the gas line is configured to attach to a gas line input of the scope accessory, characterised by: the wash line further comprising a piston in the wash container, the piston being configured to be actuated due to an increase in pressure in the wash line gas channel caused by the received gas to cause a liquid to be expelled from the wash container, the wash line wash channel being configured to transport the expelled liquid to the scope accessory, the wash line comprising a valve configured to enable the liquid in the wash container to be replenished while the wash container remains in position in the wash line, the wash line comprising a one way valve, the wash container being attached to the valve, the valve comprising an input port for receiving liquid from the wash container, an output port for transmitting liquid received from the wash container towards the scope accessory, and a refill port for refilling the wash container with liquid, wherein the valve is configured to open and close the refill port, wherein the valve is a three way stopcock, wherein the output port of the valve is connected to the one way valve, wherein the one way valve is configured to prevent liquid flowing up-stream into the valve. a wash line gas channel; a wash container; and a wash line wash channel, the wash line gas channel being configured to receive a gas from a wash line gas output of the control unit, wherein the wash line wash channel is configured to attach to a wash line input of the scope accessory, the gas line comprising a gas line channel configured to receive a gas from a gas line gas output of the control unit, and to transport the received gas to the scope accessory, wherein the gas line is configured to attach to a gas line input of the scope accessory, characterised by: the wash line further comprising a piston in the wash container, the piston being configured to be actuated due to an increase in pressure in the wash line gas channel caused by the received gas to cause a liquid to be expelled from the wash container, the wash line wash channel being configured to transport the expelled liquid to the scope accessory, the wash line comprising a valve configured to enable the liquid in the wash container to be replenished while the wash container remains in position in the wash line, the wash line comprising a one way valve, the wash container being attached to the valve, the valve comprising an input port for receiving liquid from the wash container, an output port for transmitting liquid received from the wash container towards the scope accessory, and a refill port for refilling the wash container with liquid, wherein the valve is configured to open and close the refill port, wherein the valve is a three way stopcock, wherein the output port of the valve is connected to the one way valve, wherein the one way valve is configured to prevent liquid flowing up-stream into the valve. the wash line further comprising a piston in the wash container, the piston being configured to be actuated due to an increase in pressure in the wash line gas channel caused by the received gas to cause a liquid to be expelled from the wash container, the wash line wash channel being configured to transport the expelled liquid to the scope accessory, the wash line comprising a valve configured to enable the liquid in the wash container to be replenished while the wash container remains in position in the wash line, the wash line comprising a one way valve, the wash container being attached to the valve, the valve comprising an input port for receiving liquid from the wash container, an output port for transmitting liquid received from the wash container towards the scope accessory, and a refill port for refilling the wash container with liquid, wherein the valve is configured to open and close the refill port, wherein the valve is a three way stopcock, wherein the output port of the valve is connected to the one way valve, wherein the one way valve is configured to prevent liquid flowing up-stream into the valve.