SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

We recently turned on sprinkler system on and tested it, all the heads were working fine. The next day we noticed a section of our yard was very soggy; not necessarily the grass but it felt like water was under the sod/lawn. We unplugged the sprinkler but nothing changed. We then shut off the water supply, and the next day water was gone, everything was back to normal. We didn't install the system, it was here when we bought the house and have always had a professional winterize it for us. I have no idea what could be wrong. I opened the control box and there were 5 circular knobs with 2 red wires running out of the top and between each other. I am not sure why there are only 5 when we have 8 zones (I thought it was one valve for each zone - if in fact these "knobs" are valves). There might be more but they are randomly buried throughout the box. Does anyone have any insight into what might be the problem? Our system is a TORO, Model 188-96-12 from 1998.