From its looks a spud wrench is very much like any other wrench. While some types of wrenches are capable of performing the same task, a spud wrench was designed for a very specific purpose. Changes in plumbing design have made their original function all but obsolete, but spud wrenches are still used by steamfitters, pipe fitters and other industrial workers.
A spud wrench is intended to loosen and tighten a section of piping found on older model toilets. This piece of piping was called a 'spud'. The spud wrench was designed to work on the bolts, collar and other pieces of the spud unit. The spud connected the toilet bowl to the reserve tank.
Thomas Maddock made the Maddock Spud in the early 1900's. His design was eventually bought by the "Standard" toilet company which used the spud until 1920. At that time Standard began using an expansion type spud. Each of these required a unique spud wrench for installation or maintenance.
Some spud wrenches are a set size, such as 2-inch, while others are adjustable. Most spud wrenches today are adjustable and can look very much like a large pipe wrench. There are few other applications in which a set size spud wrench would be useful.
Some spud wrenches will have two different wrench heads, one on each end of the tool. The wrench was designed to tighten or loosen not only the slip nut but the collar as well.
The original wrenches which fit only a single size spud can be difficult to locate. The adjustable wrenches can normally be found at stores such as True Value, Lowes, or Home Depot.