backups · burst pipes · leaking roof · leaks · overflow · water damage · water supply · Sep 01, 2025

How to Avoid the Most Common Causes of Home Water Damage

According to the Insurance Information Institute, (Facts + Statistics: Homeowners and renters insurance)

Water damage and freezing accounted for 27.6% of claims in 2022, up from 2021 by 4%.
Each year, about one in 60 insured homes has a property damage claim caused by water damage or freezing.
The average claim for water damage and freezing came in at just below $14,000.

(The water damage and freezing category includes damage caused by mold, if its covered.) You and your home don’t have to be part of those statistics, though! Sure, accidents happen, but think about it–insurance companies find ways to hedge their risk, and homeowners should, too. Let’s face it, fighting with an insurance company to get the proper repairs done and being inconvenienced or possibly out of your house while they are being done is not desirable. What are these types of water damage, and what can we do as homeowners so that we don’t get hit?

Let’s look at the top causes of water damage (Water Damage Statistics):

AC leak or condensation
Appliance leak
Blocked drain
Clogged gutters
Corroded pipes
Dripping faucet or showerhead
Faulty HVAC system
Faulty plumbing (including sink drains)
Faulty sprinklers
Frozen pipes
Leaky roof
Leaky water heater
Leaky water supply line (including washing machine hoses)
Overflowed tub or toilet
Sewage backup
Sump pump failure

Although these sources all involve water, there are three types of water: Clean water (from fresh water sources like drinking water supply or AC condensate), Gray water (from sinks, the shower and dishwasher), and Black water (from any water that might contain pathogens or toxins, such as flood water, sewage, seawater, and even groundwater.). Clean water damage, which is category 1, is easier to clean up and restore than Gray or Black water, which are categories 2 and 3.

Nearly all of these incidents are preventable! First of all, if you are considering buying a property, ask the home inspector to point out possible sources of water damage in the home he’s inspecting. Some of these would not trigger a repair or replacement for the immediate purchase of the home, but in the first few years of ownership, you’ll want to take care of those issues.

Next, in your existing home, make regular walks or inspections of your own, of every place in your home, including the attic, including the entire perimeter of the house, including the crawlspace, if you have one and it’s safe to do so. You’ll want to make note and take photos of stains, visible mold, warped or rotten wood or walls, pooling of water, and musty smells. A moisture meter can help you detect small leaks before you would even see them, so it’s good to have one and know how to use it (see our article!)

Let’s start at the top: AC leaks are different from condensation. The place you will be most concerned with AC leaks will be directly below the air handler (and the route of condensate drain line from the air handler to the outside). Check out this video that uses a bio-friendly cleaning agent, vinegar, to clean out the line and get rid of bacteria that can clog it up. If your condensate pan is already overflowing with water and slime, take a wet-dry vacuum outside and place the end of the vacuum hose over the end of the condensate pipe (minute 6:28 in the video) to suck out the drain clogging slime (You can also use your hand in place of the duct tape). In severe cases you may have to open up the air handler and manually clean the slime out of the drain pan as well. Make sure to include a Whole-Home Dehumidifier on this list if you have one, because these also have drains to remove the liquid condensate from the unit. Condensation is the formation of water droplets on a cold surface, because the surface temperature is below the dew point. You can get condensation on AC ducts if there’s a break in the insulation or missing insulation; condensate will also form on vents and registers sometimes, and drip on the floor. Check out our article to prevent this!

Appliance leak: Make a list of the appliances that use water in your home! These can be: Dishwashers, washing machines, refrigerators, water heaters, garbage disposals, showers, and toilets. Make sure to pass by these appliances more frequently (or better yet, place a leak detector near them) to catch any leaks quickly. You can also see if there is any residue, like dried lines of dust or water deposits, on the floor if there’s an intermittent leak.

Blocked drains cover a lot of ground. Besides the AC condensate drain line and dehumidifier drain line mentioned above, there are sink drains, dishwasher drains, shower and bathtub drains, washing machine drains, and toilet drains. This article gives a lot of useful information about the various drains in a home and their terminology. If your appliance starts to back up (like standing water in the dishwasher after it’s finished its cycle or a sink that will not drain), then it’s time to take action, before that foul water leaks out onto your floor! If it’s mildly clogged, this natural way to unclog it should work, and future maintenance with the same solution should keep them clear! In addition, if you suddenly start smelling sewer gases in an area of your home, it could signal that a vent is clogged (vents release gases into the outside air, but if they become clogged, that gas can back up into your home, interfering with drainage).

Clogged Gutters: Properly functioning gutters are super-important for the health of your home! When they are clogged, water can rot the sheathing and fascia on the roof edge, as well as allow water to enter the exterior wall, and even cause foundation problems where falling water hits the ground. You can tell if a gutter is clogged when it’s raining, by noting if water is spilling over the gutter. If it’s not raining, you might see staining on the wall or even rot and warps in the siding. Ground erosion will also occur where the water spills over. If you cannot clean your gutters, it’s time to hire or barter with someone who can, and fix any damage on the roof or wall to keep mold out of your home.

Corroded pipes: Modern plumbing materials such as PEX, PVC and ABS are more corrosion-resistant than older materials like copper, cast iron and galvanized pipe. Copper is still widely used for water supply, however, it can be corroded by iron from the water heater (check out this very informative video that also tells how to prevent corrosion of the water heater), as well as flux from plumbing joints, or excessive turbulence in the pipe. If you see one leak in your copper pipe, it’s best to get it inspected by a professional in order to make sure it doesn’t happen in other places! Cast-iron is a very old material that was typically used for gray-water and sewage drains, so you may see these under an old home in the crawlspace. Because they are so old, it’s best to replace these as soon as possible to avoid leaks of these drains under and around your home.

Dripping faucet or showerhead: Drips from closed faucets or showerheads are more than a nuisance. They signal that something is wrong with the valve that controls the water, which is usually inside the handle or wall, where water will really cause damage. If you cannot shut the faucet off completely, it’s time to take note of the model of faucet or shower valve and replace the seals or whole unit (sometimes there’s a “rebuild” kit available that only replaces the most frequently-worn parts or seals). Be sure to check if water leaked inside the wall and clean or remediate all of the associated water damage and mold.

A faulty HVAC system can leak water if the condensate pan (see AC leaks above) is below the outside drain area, and a condensate pump is needed to remove the condensate. If this condensate pump fails, water will fill up the pan and overflow. Sometimes, condensate pans corrode and leak. Finally, the evaporator coil can freeze when airflow is restricted, usually due to a dirty filter. Instead of draining away normally, moisture freezes directly on the coil. Then when your system cycles off or the ice begins to melt, all that frozen water suddenly becomes liquid again—often more than your drain system can handle. (From Drips to Disasters: HVAC Water Damage Explained) The best way to mitigate this is, of course, to set a reminder and change your filter regularly! If the filter is not the problem, call in a technician to determine why the coil froze; it could also be low refrigerant in the system.

Faulty plumbing: Lots of homeowners think, I could do this…and with or without the assistance of youtube, make plumbing repairs that are not safe or up-to-code. Sometimes even licensed plumbers are not careful to follow code or make leak-proof systems. Finally, even well-intentioned homeowners cause leaks when they use drain areas under sinks for storage (check out our article on how to avoid these). If you are unsure of how drains work, it’s really best to call a licensed, reputable plumber to do the work, instead of paying even more later to clean up a moldy mess! Ask your neighbors, friends, and even the local plumbing-supply store for recommendations. This is especially important when working with water supply lines, which can be under 35-80 pounds per square inch of pressure (which of course can flood an area very quickly!).

Faulty sprinklers: Proper sprinkler installation, even though it’s “out in the yard” is very important to the health of your home! There are several things that can go wrong: if the sprinklers are too close to the home or aimed in the wrong direction, that spray of water can quickly soak into an exterior masonry or stone wall and cause damage. If the junctions of the sprinkler system are not tight, underground leaks can run into your basement or foundation, causing damage. If you see water stains on your home siding, or water directly hitting the walls during the cycle, or pools of water in your lawn or around the foundation, it’s best to call in a landscaping company that is competent in sprinkler installation and repairs to get it fixed.

Frozen pipes can do a lot of damage! If you live in an area that can freeze, it’s really important to insulate and/or drain piping that can freeze, to avoid the expense and tragedy of water damage in your home. This video shows a variety of old-fashioned tips to keep the pipes unfrozen or thaw them out if they do freeze. However, if you are in an area that regularly freezes, it’s best to install a frost-free garden hose “bib” . Some are better than others, and the new Aquor design is more expensive (about $100-150), but is more simple to use when winterizing. This video shows the difference between the typical hose bib and the Aquor, and how to install the Aquor properly.

Roof leaks happen for a variety of reasons…age, severe weather and damage from trees and animals all work against your roof. The hardest problem is sometimes locating the exact location of the leak, because water can run for a long time under the roofing before it emerges on the inside of your home or attic. There are a number of temporary products on the market to stop leaks, but you’ll want to get the roof professionally repaired or replaced as soon as possible. This roofing professional advises against buying/using FlexSeal on a roof, and shows you how to make a temporary repair with aluminum flashing and roof sealant. Of course this job requires that you get up onto the roof, so if you cannot safely do it, hire someone who can do a good job!

Leaky water heater: Hopefully if your water heater leaks, you will catch a slow leak, not a full-on Niagara Falls waterfall! Water heaters leak for a variety of reasons. They have corrosion protection called “sacrificial anodes” inside to prevent galvanic corrosion, but when the anode gets fully sacrificed (used up), corrosion will start to attack the inside of the tank, making weak spots and eventually leaks. This can happen as soon as 3 years after the heater is installed! It’s a pretty easy process to replace these rods, one that anyone can do if comfortable with a socket wrench (however, if your water heater is gas-fired, you may have to have a plumber or licensed professional come to re-light it). Other leaks can come from the piping or valves that serve the water heater. This video shows the inside of a corroded water heater and why you should stay on top of maintaining this appliance!

Leaky water supply lines can be very messy if they are inside your house, but also costly outside the home! Because a broken pipe can spew 35-80 gallons per minute, they can easily flood your home or erode your foundation or driveway, while running up the water bill hundreds of dollars. For this reason, if you have it in your budget, get an automatic shut-off valve installed (see our article). It will detect unusually large flows and shut off the main service line so that if the leak is inside your home, you can avoid a big flood. Some systems can detect low pressure as well, which can point to a leak outdoors. The Flume Water Monitor is not a shut-off valve, but it can monitor and manage your water use, indoors and out, and notify you immediately in case of a water leak. The sensor straps around your existing water meter, no plumbing required.

Overflowed tubs and toilets are usually unexpected and costly. They usually stem from allowing the supply water to remain on, but sometimes a clogged drain can be the culprit. The supply problem can be prevented, though, by installing a water shut-off valve or monitor as mentioned above. These devices “learn” your home routines and provide alerts and/or shutoffs before the overflow.

Sewage backups are toxic and very costly. Besides having to call in the professionals to clean up, most everything the sewage touches must be replaced for sanitary reasons. Sewage backups can be caused by flooding, when runoff or floodwater fills sewage tanks and lines and backs up into the home. However, it can also happen if your home is served by a septic tank and you don’t get it pumped frequently. Sadly, a backup can also damage your septic system by clogging the drain field, possibly necessitating replacement. For these reasons, it’s important to schedule pumping the tank every two to five years (though the exact frequency depends on your household size, tank size, and water usage). If your home is on city sewage service, request a septic inspection before purchasing the home to identify any blockages in the drain line or potential problems.

Sump pump failures can come at the worst possible time–in the middle of a torrential storm–so it’s good to test them periodically to make sure they are working! You can do this by pouring a bucket of water into the sump well and making sure that it turns on and evacuates the well. Another problem could lie in the discharge piping, if it gets clogged.

If you are diligent in looking around your property, a lot of water damage incidents are preventable, so don’t “stick your head in the ground” if you see something amiss, or even hear of a neighbor’s misfortune. In this case, ounces of prevention are worth gallons of cure!

Photo by Piotr Łaskawski on Unsplash

Back to Blogs