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May 1, 2023

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    Water damage is one of the worst scenarios a homeowner can encounter. Water damage can spread toxic mold spores, ruin appliances and furniture, and even result in collapses and structural hazards. If you discover a flooded room, you will need to act immediately to quell the source of the leak and mitigate as much damage as possible.

    This guide will break down all the significant elements of water damage, including its causes, hazards, and the immediate steps you should take to resolve it. 

    Identifying Your Water Category and Class of Damage

    The Institute of Inspection Cleaning and Restoration Certification (IICRC) uses two metrics to assess water damage: water category and class of damage. The water category refers to the type of water introduced to an affected area, with each category reflecting the hazardous materials within the water. The higher the water category, the more unsanitary it is and the more dangerous it is to handle. The water damage class reflects the amount of water introduced to a location and how difficult it is to remove. 

    Understanding the classifications and categories of water damage is essential, as not all types of leaks are manageable on your own. Even smaller, lower classification leaks, if they are of a high enough category, can be highly toxic and should only be handled by professionals. On the other hand, even completely clean water, if in a high enough classification, can damage the home’s structure so much as to require restoration services. 

    What Are the Different Categories of Water? 

    Domestic water falls into three categories, some of which have respective subcategories: Category 1 (clean water), Category 2 (greywater), and Category 3 (blackwater). 

    Category 1: Clean water

    Clean water, as its name implies, is water with little to no hazardous materials. This water is the safest and is manageable by homeowners in small to moderate amounts. While usually only the cause of minor damage, in large enough quantities, it can still cause significant damage to house structures, furniture, and appliances. While also relatively clean, if not managed and removed correctly, it can turn into greywater and then blackwater quickly (within 24 to 48 hours). You most often see Category 1 water damage from the following sources: 

    • Rainfall 
    • Leaky pipes 
    • Broken appliances 
    • Toilet tanks 
    • Faucets 
    • Snowmelt 
    • Leaky roofs
    • Damaged sprinklers 

    Category 2: Greywater 

    Greywater, sometimes spelled graywater, is a type of wastewater produced mainly from appliances. It contains minor contaminants such as a dishwasher’s food particles or less hazardous chemicals from appliances. These contaminants make the water less safe to handle than clean water and dangerous to ingest, but still safe enough for homeowners to clean on their own. Greywater has two subcategories, dark and light greywater, differentiated by the water source and the hazardous materials within that source. 

    • Light greywater: This is the less dangerous of the two and comes from showers, water basins, tubs, and clothes washing machines. Light greywater contains chemicals like detergents or soaps. 
    • Dark greywater: This type of greywater contains food particles and more dangerous chemicals. Dark greywater comes from dishwashers, kitchen sinks, mop sinks, and so forth. 

    In small amounts, greywater is cleanable at home, but in large quantities can turn into more dangerous blackwater in less than 48 hours. If you decide to clean greywater at home, wear thick rubber gloves, eye protection, a face mask, and rubber boots if the water is above ankle-deep.

    Category 3: Blackwater 

    Blackwater is the most dangerous type of domestic water you can encounter. Blackwater contains dangerous pathogens, chemicals, and other hazards, making it unsafe to handle without the proper gear and training. Due to its high contamination levels, blackwater is not manageable by homeowners under any circumstances. Blackwater can lead to rapid, toxic mold growth and should be removed by a professional immediately. Sources for blackwater leaks include: 

    What Are the Different Classes of Water Damage?

    The next factor in water damage assessment is the class of damage. Water damage classification reflects the amount of water allowed to seep into an affected area, the water’s contents, and how difficult the water is to remove. The higher the classification, the more water, the nastier the water is, and the harder it will be to remove. 

    Class 1

    Class 1 refers to rooms that have been partially affected by water damage and are the lowest classification. Minor leaks, such as dripping pipes, or rooms with a low amount of porous substances, often constitute most Class 1 incidents.   

    Class 2 

    The second class of water damage reflects medium-sized leaks and rooms with moderate amounts of porous materials. Rooms with carpet, drywall, and wooden floors affected by a broken pipe would fit into this category. This class covers situations where the water has wicked up the wall 2 feet or less, has absorbed into the entirety of the carpet, and begun to seep into the surrounding construction of the room. 

    Class 3

    This class represents when the water has thoroughly soaked into the construction and support materials of the room or where the water has wicked up higher than 2 feet. When structures such as the subflooring, ceilings, flooring, floor coverings, and gypsum have absorbed considerable water, the damage reaches Class 3. This class is often the result of minor floods, significant leaks from upper floors, and damaged or ruptured water lines.

    Class 4

    Class 4 is the final level of water damage and is the most damaging. When water becomes bound (or trapped) in significant areas of the room’s construction, the damage becomes Class 4. This class represents the most challenging water damage to remove, as the water is in difficult-to-clean areas and requires special equipment to clear. Some examples of Class 4 water damage include water getting trapped inside sections of a wall, a hardwood floor absorbing water to its core, and water getting behind built-in cabinets. 

    What Are the Major Causes of Water Damage?  

    Water damage can result from numerous causes, some more common than others. If you spot early signs of water damage (such as spots on the ceiling, warped floorboards, or cracking and bubbling of paint), you should always try to find and eliminate the cause. Even if the damage is minor, it can spread, or the source may build up and become a more significant leak. 

    Leaky Pipes 

    Leaking pipes are one of the most common causes of minor water damage. On their own, leaky pipes cause little harm, but they can be signs of more significant problems down the road. A leaky pipe can be caused by water pressure issues, the pipe’s materials degrading, poor seals, or climate-induced conditions like freezing. 

    Broken Appliances 

    Another common cause of water damage is broken or faulty appliances. From dishwashers to washing machines and even water heaters, these tools can burst and flood rooms if not maintained. Be sure to always keep an eye on your appliances and have them inspected if they begin to malfunction or act strangely. 


    Floods are less likely to occur than other culprits on this list, but when they do happen, they can be devastating. Floods introduce the most dangerous kind of water to your home, potentially in massive quantities. Even a minor flood can ruin entire portions of a home, and to make matters worse, they are typically not covered under most homeowners insurance policies. If you live in an area prone to floods, your best bet is to seek out a separate insurance policy against flood and mold damage, keep an eye on weather reports, and prepare accordingly. 

    Clogged or Otherwise Broken Gutters 

    Clogged gutters are a cause of water damage that homeowners often overlook. Gutters funnel and redirect rainwater away from the home’s foundation and walls. This system helps keep your lawn, foundation, siding, and walls free of water damage. If your gutters become clogged, they cease to function, leading to water damage outside and inside the home. Be sure to clean your gutters at least twice yearly and repair or replace damaged sections immediately. 

    Leaky Roof 

    Your roof, like your gutters, is designed to protect more susceptible areas of the home. Your roof shingles are coated in a waterproof asphalt coating, followed by an underlayment that keeps moisture out. When these systems fail, water can seep into the roof structures, down into your insulation, and then into the ceiling. To stop roof leaks before they can cause severe damage, you should keep an eye out for signs of a damaged roof, such as: 

    • Curled shingles 
    • Missing shingles 
    • Clogged valleys 
    • Moss growing between shingles 

    Severe Weather

    Thunderstorms, hail, hurricanes, and even high winds can cause damage to shingles, siding, and other home sections designed to keep water out. When this happens, your home can become susceptible to water damage. Severe rainfall can also cause immediate water damage if drainage systems cannot quickly redirect the water. Severe weather is challenging to prepare for and plan against, as heavy storms can occur spontaneously. The best practice for homeowners is to ensure that their water drainage systems (like gutters, storm drains, etc.) are functioning correctly and that the roof, siding, and other structures are well maintained. 

    Clogged Drains 

    Clogged drains in the kitchen and bathroom are among the most common causes of indoor water damage. These clogs result from hair, grease, dirt, and debris buildup. Eventually, these materials clog the drain enough to prevent water from passing through, overflowing, and causing damage. To prevent this, make sure your drains are funneling water properly, and if you suspect a drain is experiencing a clog, don’t put off cleaning it. 

    Damaged or Burst Utility Pipes 

    The pipes that carry water into the home are designed to be long-lasting and durable. But these systems are pressurized to direct water to the appliances and features that need it. This pressure can degrade these utility pipes over time and, in the case of a fault or damage, cause severe ruptures that can spread water very quickly. Before a full-on burst, there are several signs of a leaking or faulty water main you can keep an eye out for: 

    • Discolored water 
    • Low water pressure 
    • “Hissing” sound coming from pipes 
    • Bubbling sound coming from pipes 
    • Foul-smelling water 
    • Puddles of water in and around the home 

    Damaged Sprinklers

    Damaged sprinklers can result in a spectacular display, sending water over a dozen feet into the air. What isn’t spectacular is the damage this causes to your lawn. A broken sprinkler head or damaged pipe can result in severe water damage to your foundation, not to mention an overly moist yard, which can attract pests. To avoid this, be sure not to set your mower deck too low when mowing, and thoroughly inspect your sprinkler system yearly during the spring. 

    Signs of Water Damage to Look For

    Basement Wall Water Damage
    © Sheri Swailes / Adobe Stock

    The evidence water damage leaves behind isn’t always obvious. It can range from a puddle on the floor to a mysterious musty odor caused by mold growing somewhere you can’t see.

    Standing Water

    The most obvious sign of a problem is a puddle of water anywhere it shouldn’t be. If it’s near an appliance, fixture or pipe, check there for damage first. That includes appliances and fixtures on the upper floor that could be causing water to leak through the ceiling and onto the floor below.

    Remember, though, if the floor is uneven, water can flow and pool somewhere that isn’t immediately near the source.

    If the water is coming from a leak in the roof, you can try to pinpoint the damage by inspecting the roof from the attic, but this isn’t always possible. Water can enter one part of the roof, then travel until it finds a weak spot to infiltrate. Having a professional inspect your roof is the most reliable way to start addressing the damage.

    Visible Mold Growth

    Mold thrives in damp conditions, so any time you find it growing, it means there’s excess moisture coming from somewhere. Household mold usually takes the form of flat blotches of black, grey, brown, orange or green, but a variety of textures and colors are possible.

    If you find mold inside a cabinet, on the floor around the sink or toilet or growing in a line on a wall containing a pipe, chances are that fixture or pipe is either leaking or sweating excessively. Mold around the windows suggests a condensation problem, but it’s still worth checking for leaks.

    On the other hand, mold growing in the cool, dark corners throughout your home, such as behind furniture, under rugs, and on the undersides of shelves, most likely means your indoor humidity is too high.

    Funky Odors

    Standing water and damp building material are rich breeding grounds for mold, bacteria, and rot. These issues typically happen with porous material, such as wood, drywall, and carpet. Often, the damage is hidden from view inside a wall or under the flooring.

    You might not see any problems, but you’ll notice a musty, earthy smell similar to damp leaves in the fall or less commonly, a dirty sock smell. If a sewage line is leaking, you’ll smell sewage.

    Cleaning the room, opening the windows, and using air fresheners won’t get rid of these smells permanently because you’re not eliminating the source. To clear the air, you’ll need to stop the leak or condensation issue, then remove or thoroughly clean the damaged material.

    Not all mold gives off an odor, though, so a lack of bad smells doesn’t always mean your home is free from water damage.

    Damaged Paint and Wallpaper

    If a pipe in the wall is leaking or sweating, or condensation is forming due to poor insulation, moisture can build up inside the wall. When that moisture seeps through, it can cause paint and wallpaper to bubble and peel, and leave brownish or yellowish water stains behind.

    Wall damage and stains that show up in a straight line, following the line of the pipe behind the wall, are clear signs something is wrong with the pipe.

    Dampness, staining, and deterioration on the lower parts of your walls suggest condensation problems caused by poor sub-floor ventilation or leaks due to poor foundation drainage. More rarely, in older brick houses, it happens because the house’s damp-proof course (dampness barrier) has failed.

    This kind of home water damage is tricky to diagnose, so contact a certified, experienced water damage specialist if you find signs of it.

    Bubbling and peeling wallpaper on walls throughout your home is more likely to come from high indoor humidity.

    Sagging Walls and Ceilings

    A severe leak can soak part of a ceiling or wall with so much water that the extra weight causes the surface to sag or bulge. This is especially common in ceilings of rooms under chronically overflowing tubs and toilets. It usually affects a small area limited to the size of the leak source, but the damage will grow if neglected. Water damage like this is a safety hazard because the ceiling or wall is a risk for sudden collapse.

    Damaged Flooring

    Wherever water in your home comes from, gravity will eventually bring it to your floor. Once there, it can seep into the carpeting, wood flooring or even tile, then move on to the subflooring and joists. Because water damage to flooring is so common, it’s a good idea to inspect your floor if you think your home has moisture problems now or has had them in the past.

    Some of the signs to look for are:

    • Stains – Lingering water can leave blotchy dark grey or brown stains on wood floors.
    • Warping and expansion – Dramatic changes in moisture levels can cause wood floorboards to warp, so they look misshapen, and gaps appear between them. If they absorb enough water, both wood and laminate floorboards can expand and turn up at the edges, leaving a raised seam between each board.
    • Buckling – Severely waterlogged wood flooring can completely detach from the subflooring and buckle into sharp peaks.  
    • Bubbling – The top protective layer and photographic layers of laminate flooring are vulnerable to water damage. If the flooring gets too wet, these layers can bubble like damp wallpaper.
    • Sagging – Wood flooring that’s suffered repeated or long-term water damage can start to rot. It will feel soft and spongy when you step on it, and eventually sag. With any type of flooring material, water can seep into the subflooring and cause sagging.
    • Cracking – Floor tiles can crack and sink if the subflooring beneath them becomes too badly water damaged to provide support.  

    What To Do if You Discover a Leak

    Finding an active leak or flooding situation in your home can be shocking or, depending on the size of the leak, terrifying. But by keeping a cool head and following these simple steps, you can quickly stop the leak and mitigate the amount of damage it can do. 

    Assess Immediate Dangers and Safety Hazards

    Leaks can be dangerous depending on the rooms they occupy. For example, leaks can cause shorts in wiring, resulting in serious electrical shocks. A leak can also weaken surrounding structural support increasing the risk of room collapse. When you find a leak, before trying to intervene, take a few moments to assess the situation and look for any possible safety hazards. 

    Disconnect Power to the Affected Area 

    You should immediately shut off the power to a room if the leak has either covered an electrical device, originates from an electrical device (such as an appliance), or has flooded to the point of covering electrical sockets. Proceed to your circuit breaker or fuse box and turn off the switches that control the flow of electricity to the flooded area. If you are unsure which circuit to switch, turn off all power through the main switch – this switch will disconnect power to your entire home and is found at the top of the box. 

    Search for the Leak’s Source 

    While some leaks can be obvious, such as a burst pipe or broken appliance, some can be deceptively difficult to identify. Many leaks originate from pipes you never see that run through walls and ceilings. In these cases, try to follow the trail of water to the source as safely as possible, and if the source is coming from inside a wall or ceiling, immediately proceed to shut off your home’s water main. 

    Disconnect Water to the Leak 

    If the leak is visible, you may be able to find a flow control valve. These are individual valves that allow appliances and specific pipes to access your house’s main water sources. These valves typically resemble small red wheels or small, silver, ovular wheels. 

    Remove Standing Water 

    Once the area is safe and the flow of water has ceased, you can proceed to remove the standing water. For small to medium-sized leaks, a wet vac is your best option, as it’s cheap, easy to use, and drains water quickly. You will need to use a pool pump or hire a professional for more significant leaks and full-on floods. 

    Take Photos

    Take photos of damaged structures, appliances, and furniture throughout the cleaning process. You will need these when you file your insurance claim. 

    Inspect for Mold 

    Alongside structural stability and electrical shocks, toxic mold is one of the leading health hazards associated with water damage. As you clean your home, keep an eye out for mold growth, and if spotted, immediately remove ventilation to the room before it spreads. Mold can be a severe problem, with certain species toxic to humans. You should always contact a professional if you notice serious mold growth. 

    Ventilate and Dry the Area 

    If no mold is immediately present, you should ventilate the area. Large box fans are adequate for small leaks and floods, but you need a dehumidifier for more significant or deep-set water damage. 

    Remove Affected Porous Objects and Catalog Them 

    As the area dries, you will want to remove all porous objects that have been saturated with water. Small objects like shirts, blankets, and stuffed animals are salvageable if washed quickly. However, anything that won’t fit into a washing machine must go. 

    Clean Location to Prevent Mold Growth 

    Once the area is dry and the waterlogged furniture has been removed, you will want to clean every surface that has been affected by the water. This cleaning will remove any immediate bacteria and kill the lingering mold spores spread by the water. Numerous antifungal soaps are explicitly designed for this situation, but a bleach solution works just as well in a pinch.

    Call Your Insurance Company 

    Dealing with water damage after a massive leak can be catastrophic, but you don’t have to go through it alone. Unfortunately, most homeowners insurance policies don’t cover floods and natural disasters, but occurrences like burst pipes or broken water mains are often covered. You should always contact your homeowners insurance company to help cover the repairs if you have encountered severe water damage. 

    Call a Water Damage Restoration Company 

    If the water damage has seeped into your home’s walls, ceiling, or floor, it may be too much for you to handle. If that’s the case, it may be time to call a water damage restoration company. These industry professionals can help get your house up and running after a flood or major leak. 

    Final Thoughts

    Home water damage is more than just unsightly. Ignore it, and it can spread, eventually rotting the wood structure of your home. The mold and bacteria buildup isn’t great for your health, either.

    If you spot signs of water damage in your home, contact a certified water damage specialist. They can diagnose the problem, then offer guidance on how to solve it and repair the damage to prevent any further harm to your home or your health.

    When faced with extreme water damage, keeping a cool head is essential. Always assess the situation for shorts in wiring, weakened structural systems, and other hazards before trying to resolve a leak. Then, once the situation is stable, you can use the information in this article to mitigate the total damage the leak has caused.

    Editorial Contributors
    Sam Wasson

    Sam Wasson

    Staff Writer

    Sam Wasson graduated from the University of Utah with a degree in Film and Media Arts with an Emphasis in Entertainment Arts and Engineering. Sam brings over four years of content writing and media production experience to the Today’s Homeowner content team. He specializes in the pest control, landscaping, and moving categories. Sam aims to answer homeowners’ difficult questions by providing well-researched, accurate, transparent, and entertaining content to Today’s Homeowner readers.

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    Lora Novak

    Senior Editor

    Lora Novak meticulously proofreads and edits all commercial content for Today’s Homeowner to guarantee that it contains the most up-to-date information. Lora brings over 12 years of writing, editing, and digital marketing expertise. She’s worked on thousands of articles related to heating, air conditioning, ventilation, roofing, plumbing, lawn/garden, pest control, insurance, and other general homeownership topics.

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