I recently bought a house that has what appears to be a good sprinkler system installed. Trouble is...it needs some repair work and I can only find two of the valves. It's an 8 zone system, so there should be 8 valves, right? I know where the main shut off valve is...and then 2 of zone control valves. I've been all over the yard to find the other 6 and CAN'T. Does anyone have any suggestions?