Hi, On demand model 80(about 9 years old, single tank model) Noticed water is leaking into brine tank in service mode. It causes the float to shut off the water flow. I believe the float is for safety for this kind of problem to prevent flooding of tank(?) Looks like something is causing the water leak inside main valve ass'y. Experts, is there a repair/rebuild kit for a problem like this? I have an original manual which came with the unit. TIA, Tony