Flapper Valve Disc Set, # 155A152 for 155, 150, 160, 163, and 168 Series Valves.
Osmonics newer part # 1033013.
Some older manuals have part # 165N109 as the part number for this SET.
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Autotrol Valve Leaking to Drain after Replacing Valve DiscsReplacing the Autotrol Flapper Valve Discs
The expected life span of the Autotrol softener control valve is 20 - 30 years with a few minor repairs along the way. The Flapper Valve Discs in the valve body generally need replacement after 15 - 20 years. However, if your system is on a chlorinated water source, the Flapper Valves ( part # 155A152 ) will need replacement much sooner ( 5 - 10 years is common ). On chlorinated water supplies it is also necessary to replace the Flow Control Ball ( part # 4F ) which sits inside the Backwash Plug on the right rear of your valve. In severe cases it made be necessary to replace the injector ( # 28F-BB ) also. There is no need to change other parts or o-rings unless you have a leak.
The flapper valve discs can be replaced by removing the 11 screws holding the top plate on ( you need to remove the cam and the timer housing first ). The flat springs pop out of the top of the valve discs. A pair of needle noses pliers helps with removing the springs ( and popping them back in place ), and also with pulling the valves out of the valve body. It is a fairly simple procedure.
PLEASE check carefully that the area where the valve disc "seat" is 100% clean, and be sure to Install the Discs into the Valve Body, and THEN lower the Top Plate on top. The Valve Discs must all be INSTALLED and SEATED first, for best possible results ( less chance of problems or leaks ).
The only other "tricky" part is to be careful putting the 11 screws back in. The screws are self tapping. I recommend turning them slowly in reverse until you feel them drop into the thread groove, then alternate tightening them down. Do not over tighten, since you are screwing metal into plastic.