For those who do not want to invest in an Apex LDS, I found this that may be useful as an alternative, and cheap.
http://www.homedepot.com/p/Zircon-Corporation-Leak-Alert-Electronic-Water-Detector-64003/100015624?ds_e_ad_type=pla&cm_mmc=Shopping|Base&gclid=CjwKEAiAw56lBRCs29jB9uOvkygSJADnD3-6S2XKhqIdF97Vw01rpbbuPXMpMqPZRH_qEcL3oMR_bBoCngzw_wcB&gclsrc=aw.ds