Locke Well & Pump Company

I would like to purchase a uni-dose U142-281 (240 volt) pump. I have had two already. One is a U142-281, and the other is a U142-281TU. One uses univalves and the other has ball valves. Which one would this be? Is one better than the other?

All Unidose pumps are now supplied with ball checks. Univalves are only used in the old style pumps.