Question
I have a hydrotek 4000 4 zone irrigation valve.  I'm getting sand in my sprinkler heads in 2 of the zones.

Answer
Hi Calvin
do you have any recent broken pipe?
If the water comes from a lake or canal probably the screen canal get to the bottom and is sucking sand.
If you are using city water could be a loosen sprinkler or a broken pipe.
Regards
Guillermo