1. A battery-operated irrigation controller comprising:a body forming a chamber having an open end;
a sealing section disposed on the body;
at least one sealing ring configured to contact the sealing section;
a cap configured to cover the open end and having a surface for contacting the at least one sealing ring to create a compression force on the at least one sealing ring to create a watertight seal of the chamber;
a retainer configured to contact the cap and engage with the body to retain the cap to maintain the watertight seal of the chamber, the retainer being separate and removable from the body and the cap;
a battery holder supported by the body and configured to receive at least one battery; and
one or more electronic components configured to receive power from the at least one battery.