Attwood Bilge Switch S3 Series - 12V [4801-7]Automatic Bilge Switch S3 Series Part #: 4801 7 Incorporates a proprietary Electronic Sensing technology to detect bilge water levels and trigger pump activation and has been engineered to operate in any bilge water mixture consistently without failure. Your pump won't be exposed to continuous cycling as the S3 switch can easily distinguish splashing bilge water, chemicals, sludge build up or foam and comes equipped with fully sealed electronics that