A well cap is a metal cover that sits on top of a well casing (almost like a lid),
although manufacturers also produce well caps that include ABS. Well caps are often designed with the ability to allow pump wire to pass through underneath the lid (most often via conduit) and there is often a grounding bolt also included. Well caps do not support submersible pumps, as any situation where a well-cap is installed will also include a pitless adaptor. A well cap is seated along the top and outer edges of a well casing, creating a seal with an integrated O-ring gasket on the outside of the well casing.
Well Seal
A well seal also sits on top of a well casing, but it serves a number of other purposes that a well cap
does not. A well seal allows for pump wire, a faucet or hose hookup, and the primary water supply to pass directly through the seal via the holes that are a part of the design of the seal. In addition to this, the well seal itself also supports the submersible pump which is suspended from the seal. A well seal is seated along the top and inside edges of a well casing, creating a seal with an integrated O-ring gasket from the inside of the well casing.
The safest bet—if you are replacing a well cap or seal—is likely to continue using what the previous installer had already used. But if you’re unaware of what was used before, or have reason to believe (in the very unlikely event) that the wrong type was used, there is a more logical way to conclude what makes the most sense for you.
