The humble chairside trap, also known as the vacuum collection canister, is the first line of defense for your central vacuum. The collection canister does more than simply trap large debris that may be picked up by your HVE valves. While trapping debris that can clog or harm your central vacuum is an important function, the collection canister allows you to have multiple vacuum valves in the room.
The canister has a single connection to the central vacuum providing vacuum into your operatory. It has three outlets to connect to your vacuum valves. It has a standard configuration of two ½” ports for the high volume evacuator valves (HVEs) and one 7/32” port for the saliva ejector (SE). These sizes are standardized in the US, as are the hoses which attach to them, so you have universal compatibility.
Above is the bottom view of the type “A” canister with the ports called out. As you can see, the HVE and SE ports are all in a line across the diameter of the canister. The drain port is larger (5/8”) on this canister and offset to one side. It also uses a metal bracket and incorporates brass inserts, which accept the mounting screws that hold the bracket. There are 4 holes, so you can mount the bracket to either side as you prefer.
The type “C” canister has the same size ports as the “A,” but the drain line comes out the side of the canister rather than the bottom. Otherwise, the ports are in the same configuration (the HVE and SE ports are all inline along the diameter) and it uses the same basket as the type “A.” The side drain allows the “C” canister to be used in locations where you need the drain to come off at a 90 degree angle, such as inside a cart or at the end of an assistant’s arm.
Type “B” canisters are slightly smaller in diameter than the “A” and “C." Its ports and drain are all off-center. As you can see below, the drain port is the same size as the HVE ports (1/2”). This is one of the distinguishing features of the type “B” canister; it has a smaller drain than the “A” and “C” canisters.
The “B” canister also has a unique clip-on connector to attach to the brackets it can be used with — these allow use of the “B” canister in tight spaces.
As far as drain sizes go, the “B” canister has a ½” drain and the “A” and “C” canisters have a 5/8” drain. With a 5/8” drain size, one might expect the type “A” or “C” canisters to allow better flow than the type “B,” but ultimately the vacuum is dependent on the HVE and SE valves (which restrict to less than ½” either way) which restrict vacuum more than either drain line will. Regardless of the canister used, the suction you get out of the valve should be the same.
Whether you’re replacing an existing canister or adding a new one, you should now know the ABC’s of collection canisters, so you’re best able to find what you need!