I have a wickes twin impellor 2 bar brass shower pump, that intermittently will not activate. It's been installed about 17-18 years. I'm guessing it's an issue with the flow switch. Does anyone know if it's possible to get at the flow switch on these pumps? I'm thinking it be may be furred up slightly and needs cleaning. I'm loathe to replace it as we will be having a new bathroom in about 18 months.