Discover the most common sources of water leaks in multi-unit buildings and how smart monitoring can prevent costly damage. Learn how proactive leak detection reduces insurance claims, protects residents, and safeguards your bottom line.
Water leaks are one of the most costly and disruptive issues facing multi-unit buildings today. From insurance premium hikes to structural repairs and frustrated residents, an undetected water leak is more than an inconvenience–it’s a silent threat to a building’s financial and operational stability.
Water is the #1 source of property insurance claims, with the average water leak causing over $65,000 in damage and displacing residents for up to three months.
The good news? Most water leaks can be detected and contained before they escalate into major issues. By understanding the most common sources of water intrusion in condos, co-ops, and multi-unit buildings, property managers and board members can take proactive steps to reduce claims, protect residents, and avoid costly emergencies.
Below, we highlight five of the most frequent sources of water leaks, the hidden costs they create, and how smart monitoring and early leak detection can transform your building’s risk profile.
This article includes insights from Paul Yelle, product specialist at ProSentry. Paul is IICRC-certified in water damage restoration, fire and smoke restoration, and applied microbial remediation. His background in emergency restoration across NYC gives him a unique lens into how early detection can save time, money, and stress for everyone involved.
Air conditioning systems are essential for resident comfort, especially in the summer. However, they also pose one of the most common risks of water leaks in residential buildings. Fan coil units can drip condensate water due to clogged drain lines or failed components. Because these systems are often tucked into walls or hidden under window enclosures, leaks can remain undetected for days.
Paul says: "Water leaks from AC units and fan coil units can be deceptively destructive and costly. Often, leaks go undetected until they've already caused damage. They seep into ceilings, walls, and floors, which can lead to microbial growth, structural deterioration, and expensive repairs. It's important to stay on top of routine maintenance, but even more important to take a proactive approach by detecting leaks before they become insurance claims."
Battery-powered water leak sensors installed in fan coil enclosures beneath the condensate pan detect leaks early, often sensing slow drips that would otherwise be absorbed into the wood floor, avoiding the need for a visual detection.
Kitchens are packed with hidden plumbing, making them a prime zone for slow, undetected water leaks. With plumbing lines hidden behind cabinets and appliances, slow drips often go unnoticed until serious structural issues have developed. While spills on the floor are obvious, cracked hoses or worn valves can leak undetected for weeks or even months.
“If you're lucky, you’ll catch a water leak in the kitchen before it spreads,” says Paul Yelle, product specialist at ProSentry. “But when ignored, small drips can snowball into building-wide issues with expensive secondary damage. Rapid response, moisture mapping, and professional drying are essential. Better yet, use point-of-leak sensors under sinks and dishwashers to detect leaks before they become costly insurance claims.”
In a mid-rise condo on Manhattan’s Upper West Side, a cracked dishwasher drain hose slowly leaked behind the kitchen cabinetry. The owner never noticed the water leak until the unit below reported water staining on their ceiling. By then, water had saturated the cabinet base, warped the engineered wood flooring, and led to visible mold growth. The water leak resulted in a $35,000 restoration bill, highlighting the high cost of undetected leaks in multi-unit buildings.
Point-of-leak water sensors installed under kitchen sinks and beneath dishwashers detect the earliest signs of a leak, often just a few initial drips. If left unnoticed, these small leaks can escalate into full pipe failures, resulting in burst pipes that flood multiple apartments. Compact and battery-operated, these sensors are ideal for tight spaces and send real-time alerts the moment water comes into contact with the sensing strip.
Bathrooms experience constant use, making them hotspots for water leaks that often go unnoticed until significant damage has occurred. Leaks under the sink, worn toilet seals, or continuously running toilets can cause significant damage over time. These issues not only affect the unit where the leak originates but also contribute to higher utility bills and complaints from neighboring units.
Paul says: "Even a small, slow leak under a bathroom sink can cause thousands in damage if not caught early. Running toilets are also a silent budget drainer, wasting hundreds of gallons per day if left unchecked. Sensors placed in bathroom vanities or near toilets can help spot issues before they escalate."
Battery-powered strip water sensors placed beneath bathroom vanities and behind toilets are discreet yet highly effective at detecting even small pools of water from slow leaks. Many of these sensors also include temperature and humidity monitoring, helpful in identifying conditions that often precede microbial growth. Additionally, monitoring repeated toilet refills through a water usage sensor can flag continuously running toilets, which often waste thousands of gallons of water without detection.
Laundry machines are one of the leading sources of sudden water leak incidents in multi-unit buildings. A cracked hose, overflowing washer, or blocked drain pan can release gallons of water in minutes, quickly damaging flooring, walls, and the units below.
Paul says, "If ignored, leaks in laundry areas don’t just damage a single unit. They often cascade down into mechanical spaces, electrical rooms, or other apartments. A single failed hose or overflow can trigger tens of thousands in damage. Installing sensors around laundry appliances is one of the simplest ways to catch leaks early and avoid cascading damage."
Water strip sensors placed at the base of laundry machines and inside drain pans provide early, reliable warning of leaks or overflows, helping prevent costly water damage before it spreads.
Every building has one, and it’s often one of the least monitored areas. Packed with plumbing infrastructure, boilers, sump pits, and HVAC equipment, these spaces are highly susceptible to a major water leak, especially when left unmonitored. These rooms are especially vulnerable to flooding when sump pumps fail or when leaks go unnoticed for hours or days.
In an Upper West Side skyscraper, a failed pump on a mechanical floor caused a significant overnight water leak that went unnoticed for a short time. Water flooded the subcellar, damaged elevator banks, and seeped into multiple residential apartments below. Within minutes, the elevators malfunctioned, and the resulting insurance claim exceeded $150,000.
Sump pit monitoring sensors provide alerts when water levels rise too high, indicating a pump failure or other issue. Rope sensors placed around floor drains, water heaters, and boiler bases detect leaking water at the earliest stages. Additionally, boiler temperature sensors can signal potential malfunctions or system failures before any visible leak occurs.
Water leaks may be inevitable, but preventing damage from a water leak is not. With the right monitoring strategy and a proactive mindset, property managers and board members can reduce claims, extend the life of building systems, and avoid costly surprises that strain operating budgets.
By addressing water leak risk areas before they become emergencies, buildings can lower repair costs, reduce insurance premiums, and deliver a better experience for residents. It’s a smarter way to protect your property, your reputation, and your bottom line.
Water leaks are one of the most costly and disruptive issues facing multi-unit buildings today. From insurance premium hikes to structural repairs and frustrated residents, an undetected water leak is more than an inconvenience–it’s a silent threat to a building’s financial and operational stability.
Water is the #1 source of property insurance claims, with the average water leak causing over $65,000 in damage and displacing residents for up to three months.
The good news? Most water leaks can be detected and contained before they escalate into major issues. By understanding the most common sources of water intrusion in condos, co-ops, and multi-unit buildings, property managers and board members can take proactive steps to reduce claims, protect residents, and avoid costly emergencies.
Below, we highlight five of the most frequent sources of water leaks, the hidden costs they create, and how smart monitoring and early leak detection can transform your building’s risk profile.
This article includes insights from Paul Yelle, product specialist at ProSentry. Paul is IICRC-certified in water damage restoration, fire and smoke restoration, and applied microbial remediation. His background in emergency restoration across NYC gives him a unique lens into how early detection can save time, money, and stress for everyone involved.
Air conditioning systems are essential for resident comfort, especially in the summer. However, they also pose one of the most common risks of water leaks in residential buildings. Fan coil units can drip condensate water due to clogged drain lines or failed components. Because these systems are often tucked into walls or hidden under window enclosures, leaks can remain undetected for days.
Paul says: "Water leaks from AC units and fan coil units can be deceptively destructive and costly. Often, leaks go undetected until they've already caused damage. They seep into ceilings, walls, and floors, which can lead to microbial growth, structural deterioration, and expensive repairs. It's important to stay on top of routine maintenance, but even more important to take a proactive approach by detecting leaks before they become insurance claims."
Battery-powered water leak sensors installed in fan coil enclosures beneath the condensate pan detect leaks early, often sensing slow drips that would otherwise be absorbed into the wood floor, avoiding the need for a visual detection.
Kitchens are packed with hidden plumbing, making them a prime zone for slow, undetected water leaks. With plumbing lines hidden behind cabinets and appliances, slow drips often go unnoticed until serious structural issues have developed. While spills on the floor are obvious, cracked hoses or worn valves can leak undetected for weeks or even months.
“If you're lucky, you’ll catch a water leak in the kitchen before it spreads,” says Paul Yelle, product specialist at ProSentry. “But when ignored, small drips can snowball into building-wide issues with expensive secondary damage. Rapid response, moisture mapping, and professional drying are essential. Better yet, use point-of-leak sensors under sinks and dishwashers to detect leaks before they become costly insurance claims.”
In a mid-rise condo on Manhattan’s Upper West Side, a cracked dishwasher drain hose slowly leaked behind the kitchen cabinetry. The owner never noticed the water leak until the unit below reported water staining on their ceiling. By then, water had saturated the cabinet base, warped the engineered wood flooring, and led to visible mold growth. The water leak resulted in a $35,000 restoration bill, highlighting the high cost of undetected leaks in multi-unit buildings.
Point-of-leak water sensors installed under kitchen sinks and beneath dishwashers detect the earliest signs of a leak, often just a few initial drips. If left unnoticed, these small leaks can escalate into full pipe failures, resulting in burst pipes that flood multiple apartments. Compact and battery-operated, these sensors are ideal for tight spaces and send real-time alerts the moment water comes into contact with the sensing strip.
Bathrooms experience constant use, making them hotspots for water leaks that often go unnoticed until significant damage has occurred. Leaks under the sink, worn toilet seals, or continuously running toilets can cause significant damage over time. These issues not only affect the unit where the leak originates but also contribute to higher utility bills and complaints from neighboring units.
Paul says: "Even a small, slow leak under a bathroom sink can cause thousands in damage if not caught early. Running toilets are also a silent budget drainer, wasting hundreds of gallons per day if left unchecked. Sensors placed in bathroom vanities or near toilets can help spot issues before they escalate."
Battery-powered strip water sensors placed beneath bathroom vanities and behind toilets are discreet yet highly effective at detecting even small pools of water from slow leaks. Many of these sensors also include temperature and humidity monitoring, helpful in identifying conditions that often precede microbial growth. Additionally, monitoring repeated toilet refills through a water usage sensor can flag continuously running toilets, which often waste thousands of gallons of water without detection.
Laundry machines are one of the leading sources of sudden water leak incidents in multi-unit buildings. A cracked hose, overflowing washer, or blocked drain pan can release gallons of water in minutes, quickly damaging flooring, walls, and the units below.
Paul says, "If ignored, leaks in laundry areas don’t just damage a single unit. They often cascade down into mechanical spaces, electrical rooms, or other apartments. A single failed hose or overflow can trigger tens of thousands in damage. Installing sensors around laundry appliances is one of the simplest ways to catch leaks early and avoid cascading damage."
Water strip sensors placed at the base of laundry machines and inside drain pans provide early, reliable warning of leaks or overflows, helping prevent costly water damage before it spreads.
Every building has one, and it’s often one of the least monitored areas. Packed with plumbing infrastructure, boilers, sump pits, and HVAC equipment, these spaces are highly susceptible to a major water leak, especially when left unmonitored. These rooms are especially vulnerable to flooding when sump pumps fail or when leaks go unnoticed for hours or days.
In an Upper West Side skyscraper, a failed pump on a mechanical floor caused a significant overnight water leak that went unnoticed for a short time. Water flooded the subcellar, damaged elevator banks, and seeped into multiple residential apartments below. Within minutes, the elevators malfunctioned, and the resulting insurance claim exceeded $150,000.
Sump pit monitoring sensors provide alerts when water levels rise too high, indicating a pump failure or other issue. Rope sensors placed around floor drains, water heaters, and boiler bases detect leaking water at the earliest stages. Additionally, boiler temperature sensors can signal potential malfunctions or system failures before any visible leak occurs.
Water leaks may be inevitable, but preventing damage from a water leak is not. With the right monitoring strategy and a proactive mindset, property managers and board members can reduce claims, extend the life of building systems, and avoid costly surprises that strain operating budgets.
By addressing water leak risk areas before they become emergencies, buildings can lower repair costs, reduce insurance premiums, and deliver a better experience for residents. It’s a smarter way to protect your property, your reputation, and your bottom line.
Insights, innovations and updates from the ProSentry Knowledge Base
Learn how to build an effective emergency response plan for water leaks. Discover how smart sensors and real-time alerts from ProSentry help you act quickly and reduce costly water damage.
At InsurTech Hartford, John Rusk of ProSentry shares how low-cost, user-friendly IoT solutions with proven ROI are crucial to driving better adoption in the property and insurance industries.
Learn how to build an effective emergency response plan for water leaks. Discover how smart sensors and real-time alerts from ProSentry help you act quickly and reduce costly water damage.
Explore the Knowledge Base
