Question
I have an irrigation system with 5 zones with 5 heads each.  The first zone has very low pressure and the other zones are not that good either.  The pressure before and after the backflow preventer is about 65lbs.  The valves all look good and seem to operate fine.  I cannot see any obvious areas where a leak in the lines could be.  What would I do next in order to solve this problem?

Answer
Gary,

Have you checked to make sure that all of your ball valves and gate valves are turned on all the way for the irrigation line and for the house supply? A ball valve is one that has a lever and a gate valve has a round knob. If you have a gate valve people tend not to open them all the way.

It sounds like you have a water flow restriction. Are you able to do a flow test? If you can find a 3/4" line that you can get water out of then take a 5 gallon bucket and time how long it takes to fill the bucket this will give you your flow rate.

Sometimes debris can restrict water flow through meters and or back flow devices.