I've got a hunch my Aquatec 8800 has died. I flush my membrane for a minute or so when I start up my RO system and then flip a valve to direct water through the restrictor. When I do this I hear the pump noise change considerable.....it sounds like it's working harder. It's been this way since I installed the pump about 12 years ago or so. I went to make water today and did my normal thing, but when I flipped the valve, no change in pump noise....just the regular hum when I'm flushing. I do not have a pressure gauge on my antique RO unit, so no idea if the pump is raising the pressure. It's the lack of change in the noise that has me concerned it's not working. Anyone know these pumps?