If you are using fresh clams, place the water and the clams in a large kettle with a lid. Bring the liquid to a boil in the uncovered pot, then lower the heat to medium, cover the kettle, and cook the clams until they open. With tongs or a slotted spoon, remove the clams from the liquid as they open (discard any that have not opened after 7 minutes of steaming). Reserve all the liquid. When the clams are cool enough to handle, remove the meat from the shells. (If the shells are intact and nice-looking, you can separate the halves, boil the shells in water to remove all traces of fishiness then dry and store them for use as hors d'oeuvre containers

Finely chop the clam meat, and set it aside (refrigerate the clams if you will not be using them within 1/2 hour). You should have about 1-1/2 cups of chopped clams, but a little more or less will not matter. If you are using canned clams, drain them, set them aside, and reserve the liquid.

Strain the clam juice from the cooked live clams through several layers of cheesecloth or a fine-meshed sieve into a 2-cup measuring cup, and set the juice aside. If necessary, add water to make 2 cups of liquid.

To prepare the chowder, in a 5-quart or 6-quart pot or Dutch oven with a nonstick surface, cook the Canadian bacon for about 1 minute, stirring it constantly.

Except for the reserved clams, add all of the remaining soup ingredients, including the reserved tomato liquid. Bring the chowder to a boil, reduce the heat to medium-low, and simmer the chowder for 15 minutes.

Add the reserved clams, simmer the soup for another 15 minutes, remove the bay leaf, and serve the chowder.