Originally Posted by Sawdustguy
The reason for the magnetic head pump that the output can easily be restricted by a valve. The magnetic pump will simply slip when the output is restricted but a normal pump will probably burn up. This is very handy when fly sparging and you are trying to match flows.
Any centrifugal pump can have it's outlet restricted and it won't hurt it. Sanitary centrifugal pumps are used in most pro-brewery applications. The main reason mag pumps are used in home brewing rigs are: "Shaft-drive pumps require periodic maintenance of their seals. If the seals should start to fail, air can be sucked into the pump, aerating the hot wort or infecting the cool wort. Neither of these situations is desirable. Magnetically coupled pumps eliminate these worries." Brewing Techniques.
A sanitary rated centrifugal pump does cost quite a bit. when producing a product for general consumption it is best to use only materials that are food grade.
Drop me a PM next time you come down to the flatlands. I'd be honored to show you my rig. Maybe we could visit the Bull & Bush brewpub. Their system is cobbled together from various bits of old dairy equipment.
I was fortunate enough to only brew on commercial made gear.