I have two bathrooms that have been completed in the last year. Both have the same Price Pfister rough-in valve. One is sticky and requires a bit of force to turn on the water (turns on by pulling). It actually has gotten worse over time. The other turns on with a gentle pull of handle. The plumber that installed the sticky one may have pulled out the cartridge and messed it up (rationale: because he messed up other things). I'm wondering if this sounds like something I might be able to fix or should I get a new cartridge? The valve in question is a [Pfister 0X9 Brass Single Control](http://www.homedepot.com/p/Pfister-0X9-Brass-Single-Control-CC-x-CC-Mixing-Valve-Less-Stops-0X9-010A/100013032#.UUZUC9HEpZ8).