A watertight electrical compartment for use in an irrigation device can include a compartment body having a chamber and a sealing section configured to mate with one or more sealing rings. A sealing cap can mate with the sealing section and/or the sealing rings to seal the chamber. A cap retainer can be advanced over at least a portion of the sealing cap. One of the compartment body and cap retainer can have internal threads to be screwed onto external threads of the other one of the compartment body and cap retainer. The cap retainer can also have a stopping feature to keep the sealing cap in its sealed position. The watertight electrical compartment can be used in a wireless flow sensor assembly, a battery operated irrigation controller, and/or a battery-operated central controller device, to provide irrigation control, and/or sensor information, without the need for AC power.