system draws water from a lake. recently pulled the screen from mthe lake to clean. water drained from system. upon restart water pressure appears to increase and decrease intermittently as heads pop up full force and gradually lower back down. not water hammer as no sound is heard.
Does this mean there is air in the water lines? If I run the system will it eventually clear out or will I burn up a pump?
There is air in the pump or intake line that you need to get out.
Basically you need to reprime and get all the air out, the easiest way is to have a hose connection set up just a little after your foot valve of the intake line and connect a hose up to it. This way your pushing the water and air through the intake line instead of just filling the line up at the pump with air still inside. Then continually turning on/ off the zones until the pump is primed. Sometimes if you manually turn on several of the zones ( Still within the limits of the pump) this helps pushing the water because it's asking for more demand
There should be an isolation valve between the pump and the system, and a drain valve between those, which will let you more easily prime the pump. Let the air exit the system by way of the drain valve, then open the isolation valve.