What Causes Basement Flooding? Understanding the Complex Science of Water in and Around the Home

Water seems so simple most of the time. We know it as a life-giving necessity, as well as a basic element. Sometimes we call it by its chemical name, H20. We need it daily for drinking, washing, cooking and other important tasks. If we think about news headlines, we know that water can and will show up in the wrong places at the wrong time. It holds the potential to wreak havoc, damage property and take lives.

Nobody can fully predict nature or protect themselves against natural disasters such as hurricanes, storms with heavy rain, fire and downed trees, but there is a wealth of information available about water its good and bad effects. Some people expect water in the basement after rain, but other causes of minor and major flooding are less obvious.

Water is complicated, complex, mysterious and precious enough to command its own specialized science: hydrology. This science deals with the properties, distribution and circulation of water on and below the Earth’s surface and in the atmosphere. Hydrology includes surface water like oceans, lakes and rivers and the groundwater that runs below them, as well as various water tables, underground reservoirs and weather patterns.

Humankind draws upon all these different resources for its needs, mostly by drilling wells. Cities store and pump the water to city residents, while people or businesses outside the limits of municipal services access water with a private well and pump.

You don’t have to become a hydrologist to protect your family and interests from the negative effects of water. The reasons for basement flooding are varied, so it will benefit you to approach your water problem from a broad perspective.

Somewhere along the way of your mini-course in hydrology, you’re likely to answer this popular question: Why do basements flood? The more you know, the better you can prevent trouble in the future.

Know the Statistics

The National Flood Insurance Program offers tools that allow us to calculate the approximate cost of damage from floods of varying severity, from a few inches to several feet of water. For example, the cost to repair a 1,000-square-foot home that sustained three inches of floodwater would be around $11,450. For two feet of water in the same size home, the cost to restore it to a livable condition would be $33,700.

In a 2,000-square-foot home with three inches of floodwater, it would cost about $22,590 to repair damage. If two feet of water invaded the same home, the repair cost would land around $62,880.

NFIP arrives at these totals by estimating the cost to replace what would be ruined in varying levels of water, along with cleaning expenses, such as:

• Plumbing
• Electrical
• Furnace/AC unit
• Doors
• Appliances
• Trim
• Drywall
• Insulation
• Carpet
• Paint
• Outlets
• Fixtures
• Furniture
• Electronics
• Bedding
• Clothes
• Personal items

Depending on the cause of the flood, the invading water might be dirty, such as septic and sewage, or clear such as storm water. Dirty water commands more expense and additional cleanup efforts, but recovering from a flood of either kind of water will carry significant cost.

Know the Causes for Water in the Basement

You will know if a natural disaster has occurred, such as a dam or levee breaking or a huge storm or damaging fire, but other flooding-in-the-basement causes are many, varied and sometimes subtle. Water travels amazingly well and fits through the tiniest of cracks and spaces. The more you know about what can and does happen with it, the better equipped you’ll be to manage and prevent problems.

Bruce Tschantz, hydrologist and professor emeritus at the University of Tennessee Knoxville, estimates that 75% of people with water in their crawlspace or basement have the problem due to improper or inadequate roof-water drainage. Besides a gutter system and good, sloping drainage, you may have water in the basement for many other reasons, such as:

1. Clogged gutters or misdirected water. Gutter downspouts should dispense water at least six to 10 feet away from your home, sometimes farther depending on the type of soil you have. If it is clay soil, you might be safe at five feet from the home. If your soil is sandy, consider going even farther than 10 feet. Not everyone realizes how much water collects and concentrates from their rooftop and other impervious surfaces to flow toward or along their homes. If the water is not properly directed away from the home, it will cause flooding.

2. Sprinklers. Home irrigation systems do a great job of keeping the lawn green and the flowers in bloom, but the underground pipes that feed them often spring leaks. Also, if the system is not calibrated correctly, it could be sending water straight to your foundation without you knowing. Professionals can check these systems, but you can watch to see where the water squirts. For example, does it hit the house and run down the wall? You can also look for soaked areas in the ground that might indicate subsurface leaks.
3. Storm sewer backup or blockage. The pipes and other parts of the systems that receive and carry away storm water become clogged with tree debris and other materials that end up in the municipal water system. This can lead to a backup. You might be able to see the source, such a storm drain plugged by something or one that has water spurting out of it and not into it. Not many people recommend clearing debris yourself because the city is responsible for the systems. During a raging storm is not the time to search out or clear debris, but if you see a storm drain blocked by a tree branch, big rock, piece of trash or other obstacle in dry weather, you can clear it away.
4. Groundwater. The complicated route of water runs in front of our eyes in rivers, lakes, streams and swamps, as well as out of sight beneath our feet. A watershed includes the entire area where water from certain bodies may drain, flow and travel, such as the Oswego River/Finger Lakes watershed. Watersheds might be only a few square miles or, more commonly, tens or hundreds of square miles in size. Each watershed usually has an association or committee that acts as a sort of guardian, but the entities typically have maps and good information about what is happening within the watershed that might affect your property.
5. Subdivision changes and design. As housing areas mature, the landscape around neighborhoods can change. The ground itself settles and areas that were once green get paved and have water running across them rather than soaking into them. While most are sound, it is possible for the overall master plan of certain subdivisions to be flawed in their designs of slope or grade or be affected by erosion. Systems may not handle water like designers expected, or they can be undersized and need a capacity upgrade. You can always talk to neighbors in the area or staff members from the city engineering department to see if anyone else nearby is having difficulty. If considering a site for building, be sure to research its potential for flooding and erosion, as well as double check the soil and subsurface materials.
6. Slope, grading or drainage. Modern and ideal building standards state that homes should sit on a gentle mound that grades downward 6 inches within the first 10 feet moving away from the house. Clay-rich soil and a complete gutter system helps to carry water away from the home, and splash guards around the foundation add water protection. For extreme cases, you can hardly pick the house up and put dirt underneath to elevate it, but you can excavate, add and re-contour the soils around the house to get gravity working for you and water moving away from the home.
7. Sewer or septic blockage. Much like the storm-sewer drains can become blocked by debris, so can both city-sewer systems and private septic systems. That blockage will send “grey water” into places you definitely don’t want to see it, and this is an urgent matter. Most people take care of this problem as soon as possible, but if the blockage happens to be in the city’s right-of-way, homeowners can sometimes recoup some costs for repair or flooding caused by the faulty utility. Homeowners can also ask their city to do a check on its side of the system to see if any blockage exists, but most municipalities flush and clean their utility systems periodically.
8. Septic pump failure. A failed septic pump can result in a grey water invasion or overflow. Here’s a real-life example: A couple had a walk-in basement with a lightly capped roughed-in pipe for a future toilet, but when the septic pump froze during a cold snap, the cap popped off and 4 inches of nasty, smelly water bubbled up into the basement. The story emphasizes the importance of investing in a good-quality and properly installed pump, as well as regular maintenance of it. Some people even install a battery-powered backup pump in case the primary one fails due to freezing temps, power outage or other reason.
9. Foundation drainage. Directing water away from foundation walls is a key step to prevent basement flooding. Ideally, each of the main corners of a home will have some kind of system to drain water away from the foundation, and if a home does not have a system, it can usually be added. Gutters are rarely enough to carry away all the water that can affect your home. Foundation drainage might be in the form of a French drain, perimeter drain or footing drain, each of which work a little differently but toward the same goal of catching water and carrying it away from your foundation and basement walls.
10. Supply or utility-line failure. You will usually know via a notification if your local or regional utility has experienced some kind of failure that will affect your supply and/or drainage. While you cannot predict or prevent these flood causes, there might be opportunity between the notice and the possible effects to at least get belongings to higher ground and prevent some types of damage.
11. Heavy rains or melting snow. These weather events may seem obvious, but they can surprise homeowners because storm water and melting snow can travel hundreds of miles and come to affect local rivers and watersheds. You can reduce the surprise factor by tuning in to the regional weather reports. Seasonal water problems can normally be managed with one or a few measures, and you probably know about what level of protection you need or want. Naturally, it’s expensive to build protection against severe weather.
12. Inadequate or non-functional seepage tiles. Seepage tiles are routinely placed around the foundation wall of a home, inside and/or out. They create an essentially impermeable barrier that keeps the water out, and there are other options such as “geo textiles” and other membrane-type barriers that work similarly to keep your basement dry.
13. Floor and wall sealing. If and how the walls and/or floors are sealed can make a difference in how your basement resists or allows moisture. For example, tar is a somewhat old-fashioned example of a home-foundation sealant. While the sealant is not the major problem in most cases and does need to be re-applied every so often, it can help lock out condensation and other moisture.
14. Sump pump failure. When people live where there is lots of water in the ground, the homes often have a pump built into the basement floor. Pumps constantly work to move water out and keep it away from the basement. Like any piece of equipment, they fail or break and require regular inspection, maintenance and repair when needed. Like the crucial septic pump, many people have a backup sump pump.
15. Floodplain. Find out if your home sits in or around a floodplain or wetland. Floodplain maps change and so do water characteristics, so the situation from the time you and others buy their home can change, just like the flow of surface and underground waters.
16. Leaky or clogged water heater. Utility appliances need to be monitored and maintained to help them work efficiently and prevent breakdowns, especially where water may be especially hard or soft and cause buildup inside or outside of appliances.

Learn How to Protect and Prevent

You may want to consider a professional inspection or consultation, but you can do a walk-around and look at the foundation inside and outside. You can to check for cracks, crumbles or any other signs of deterioration. Gear up and go into the crawl space with a good flashlight and look for any signs of water as well as tiny spaces where water could enter the foundation or soil around it. Make a note of whether you have sand or clay soil.

Learning the water characteristics in your area can help you gauge the likelihood of flooding in your basement or property. Many people feel better doing this research themselves rather than leaving it to someone else.

Flood insurance protects against the devastating effects of an incident that can ruin property and rack up costs. Most home-buying processes involve a thorough check of the property title and history, but not everyone is thorough in the floodplain portion of their research.

It is easy to breeze through with your buyer’s, bank and title agents all telling you the home and land are not in a floodplain. In most cases that is true, but keep in mind that everyone involved in the home-sale process stands to make money off your sale and may not be as concerned as you are with flood potential.

Before you refuse flood insurance based on all the agents’ opinions, know that you too can review the Federal Emergency Management Agency’s floodplain maps, which are subject to change periodically. The price of flood insurance depends on how much protection you want and the likelihood of your property flooding within the mortgage-loan period, usually 30 years or in some cases 15.

FEMA and professional hydrologists analyze historical data to determine flood-level zones that are then expressed as ranges from a five-year floodplain to the 100-year flood level and beyond. Cities decide to what standard they will build their water utilities, such as the 25-year flood level or the 50-year flood level.

You can also call the local engineering department to ask them about flood-prone areas. You can also ask to see hydrology maps of the city or town. Some people’s strategy includes seeking out someone who has lived in the area for a long time and asking them about what areas flood and how often. You can always try to catch someone in the neighborhood to chat about water and how the streets drain. There are many other governmental resources such as the Army Corp of Engineers at the federal level and county or city departments.

Especially in older neighborhoods where streets and utilities may not have been upgraded in a while, it will benefit you to ask a few questions even when things look well in dry weather. If there are any reasons for concern, you’ll learn about them from a few casual conversations or by looking at the current flood maps.

Learn What to Do About Water in the Basement

Cleanup from a flood can be overwhelming, but keep safety as the first priority. It is important to know:

• If natural-disaster flooding is anticipated, turn off electricity to the home. If it floods while the electricity is on, call the power company before entering the flooded basement.
• Until major-flooding danger passes or until you are sure of the flood’s source, turn the water off to your home at the main valve.
• If you have a well and it’s been overwhelmed with floodwaters, it should be disinfected before you resume using it.
• If any item will dry within 24-48 hours, it has salvage potential. If not, throw it away.
• Get heavy-duty rubber gloves, goggles and some type of face-mask filter.

Experts say to not let anything sit for long. For example, carpet can be saved if crews get to it within the first 24-36 hours. The point is to immediately toss or start to dry anything that has the potential to mold or mildew.

You will probably know if your floodwater is dirty, such as sewage after the frozen septic pump, or clean, such as water from heavy rains or roof drainage. The first step for either type is obviously to remove the water then wash the entire area with soap. If your invasion was dirty water, you need to disinfect after washing with ¼ cup of unscented bleach to a gallon of water.

Keep no edible goods that could have been touched by floodwaters, such as those with a screw-on cap, home-jarred lid, snap-on top or other supposedly water or airtight seals. Canned goods may be kept if you wash them with soap and water and remove the label. Be sure to write the expiration date onto the can before throwing away the label.

You can get more tips about what to do when the basement floods. Contact Mr. Rooter or use city, county, state and federal resources such as departments of health and FEMA.

Trust Mr. Rooter

You do not have to face your basement-flooding problems alone. You have a partner in Mr. Rooter of Oneida-Utica-Rome-Syracuse. We can be on hand 24 hours a day, seven days a week and offer expertise that ranges from emergency service for burst pipes and system inspections to repairs and upgrades.

We can help with system setup, maintenance, improvement and more for any residential or commercial client, including a strategy to resolve your flooded-basement or other problems. We look forward to hearing from you and to helping manage your water needs.