Denise,
Medela has a vacum gauge that can test pump pressures but it is very expensive.
We bought a pressure gauge at an auto supply store, borrowed the Medela pump
guage from someone who had one, compared the pressure. We then rigged up the
pressure guage so we can test both Classic pumps as well as Lactinas. We now
regularly test our pumps when they are returned and we are cleaning them. Hope
this info helps.
Yaffa Stark, MA, IBCLC