I've never had a sprinkler system before, but recently bought a house with a six-zone system. The main controller is an Irritrol Rain Dial, but the heads/nozzles are a mix of Toro, Hunter and Rain Bird. The system is programmed the way I want it, and the 9 volt backup battery has been changed so if the power goes out I'm still in business. I'm pretty mechanically inclined, and had no problem replacing some nozzles and a head that apparently was parked on by a contractor. So now three of the six zones are up and running fairly well. The only problem I see with them is that a few of the pop-up nozzles won't retract the last 1/4". A friend said silicon grease might fix that, but if it comes to it I don't have a problem replacing the heads, as I might want to change the coverage area at some point. My problem is with the next zone I'm working on, Zone 4. From what I can see, there are only two heads on this zone, along a fence and about 10' apart. When I run a manual check for that zone (15 minutes) the water barely come out of the heads, and the nozzles don't pop up. I would equate the pressure to that of slowly pouring out a glass of water. In my mind I'm speculating that a) there is a break/leak in the PVC pipe somewhere, or b) a valve is not functioning correctly. What is the best way to troubleshoot this? I've run two 15 minute cycles to see if the ground gets wet anywhere that might identify a leak, but haven't see anything. If I designed the system I would have put an access box somewhere to gain access to any parts that might need to be replaced, but I don't see anything other than the main valve box, just downstream from my city water service box. There are two standard cutoff valves in the box, both open. Based on experience and the statistics, what is the problem most likely to be, and how do I go about fixing it, both finding the problem and replacing any electrically activated parts? For what it's worth, when I manually run the first three zones I hear the flow of water kick in to the sprinklers because my hot water heater is right next to the timer control box and the cold water line transmits the sound. When I manually start Zone 4 I don't hear anything, so I'm really hoping this isn't a leak somewhere. I also have one other question. I'm guessing the system is constantly charged with water up to every electrically operated valve. When winter rolls around is there a best practices kind of procedure to drain the system so it doesn't freeze? Thanks for any help provided.