Getting a water alarm like that shown below is an inexpensive way to avoid expensive water damage repair costs.  Remember that you are responsible for any damage caused by your unit or appliances.  This includes damages to your unit, your neighboring units, common elements, and utilities.  These alarms are less than $10 and are battery operated so there is no wiring required.  I suggest one at each water using location in your unit including water heaters, clothes washers, dishwashers, and under sinks.  Battery can last up to 5 years and alarm is 110dB so it can be heard throughout the house.  Alarm will sound for up to 3 days depending on battery life, but can be quickly shut-off upon response to the incident.  Can be purchased at Home Depot stores for under $10, or online by clicking http://www.homedepot.com/webapp/wcs/stores/servlet/Search?keyword=watchdog+water+alarm&langId=-1&storeId=10051&catalogId=10053