On page 19.of the manual for Autotrol 255 valve 460i control, Preventitive Maintenance - #3 “relieve system pressure by opening valve #5 (at rear) with a screw driver. We can’t find this valve. we are trying to clean the injector and screen. any help would be hugely welcome. thanks in advance.

I just bought a house with a GE brand, model PNSF35B00 water softener already installed. Previous owners said in disclosure documents that they "didn't know" if the unit worked. The salt tank is about 1/3 full of salt but there was no water in the tank (salt was bone dry). I ran the regeneration a couple times and still no water. I poured about 10 gallons of water in the tank so the water level is the same as the salt now. I ran another regeneration and the water level didn't go down at all. Couple questions. There is a large (~3") black tube that has a float in it, and a smaller black tube (~3/8") tube running into it that comes off the side of the control unit. I'm guessing this smaller tube is what pulls the brine out to flush through the resin tank. Does the unit replenish the water to the salt tank through this same tube? The other question: There is a diagram under the lid for disassembling the venturi/screen apparatus for cleaning. It looks like this unit has two different "flow plug" (tiny rubber grommet-type thing), one above the venturi and one below. It seems the upper flow plug is missing. Would this cause no flow in either direction? Is there anything else I should be look at?