Drywall Mud Pump
Drywall mud pumps are essential if you are going to use automatic taping tools. Typical drywall pumps are simple lever action pumps that sit in a 5 gallon bucket of mud. They have about a 3 inch tube that reaches to within a couple inches of the bottom of the bucket and sucks drywall mud from the bottom.
Picture of a drywall mud pump
The spout on these pumps is approximately 5/8" in diameter and located at the base of the lever which sits near the top of the 5 gallon bucket. The spouts also come with a small metal tube flattened on one end that serves as an adapter to fill taping boxes. You can also attach a goosneck to the spout which allows you to fill a drywall bazooka with drywall mud.
Picture of a Drywall pump goosneck attachment
Drywall pumps should never be used with hot mud, or quick setting drywall mud. Quick setting drywall mud hardens by means of a chemical process, therefore it can easily harden inside of the pump before you have a chance to clean it out.
There are pneumatic drywall pumps on the market as well. They are usually sold in conjunction with specific tools. For example, the "Apla Tech" taping system is centered around a pneumatic pump system.
There is not much reason to invest in a drywall pump if you plan on using no more than basic taping tools like pans and knives. However, if you choose to invest in automatic taping tools including flat boxes, angle boxes, a bazooka, the mud runner or any of these types of tools, you will need to make sure you have a reliable drywall pump.