Can this be mounted?

Yes you can definitely extend this wire by splicing into the existing wiring. It can be extended up to 300 ft. Also remember to have the contacts at a level place in which if water touches, it will touch both contacts at the same time therefor closing the circuit and allowing the alarm to sound. The alarm is 110 decibels and should be tested for sound before deciding to leave the box inside or outside of the closet. For your situation outside may be best for a clearer alarm sound. Please contact us directly at 800.991.0466 ext 3 for tech support for more information on this. We would love to help.

Yes, you can mount this.