How to Diagnose and Remedy Basement Flooding Problems

How to Diagnose and Remedy Basement Flooding Problems

It’s Safe to Say Basement Flooding is a Big Deal in Plumbing

If you’re a victim of flooded basement, we’ve got the help you need. If your basement is flooding you’re probably asking yourself a bunch of questions. How do I fix basement flooding? How do I repair my basement so it doesn’t flood? Why do I have wet basement walls? What can I do to water proof my basement walls? What shoes do I wear when I’m trying to fix the water damage? Why does my basement flood, I’m on a lot that’s higher than my neighbor’s? These questions and many more will be answered in this article.

Basement Flooding

We Haven’t done a Good Job Explaining the Details

It’s surprising how little people what causes basement flooding. What’s even more surprising is the fact that no one seems to explain it correctly or in a way that is easily understood by the homeowner.

Let’s first start by saying that your foundation is akin to a big concrete boat. When the ground is fairly dry your foundation sits comfortably in its resting place. However, when the ground is saturated, your foundation is actually being forced out of the ground. If it didn’t weigh many tons it would pop right out of the ground. The weight keeps it from coming out of the ground, preventing further damage.

Hopefully, that gives you an idea of how water affects a foundation hydraulically, in fact, it is aptly named hydraulic pressure or hydrostatic pressure. When water is present in a basement or crawlspace both the home and business owner immediately panic. What are the causes of this? What’s the best way to fix it? This is completely understandable especially when most people keep valuables, records or collectables in their basement and if you’ve spent your hard-earned dollars on finishing your basement, forget it, you call a plumber for help.


If you’ve had flooding issues in the past the alarm bell automatically goes off in your head when it starts to rain. You’re thinking “what’s gonna get damaged?” “how am I gonna clean this up?” “how can I keep the mold out of the basement?”. The pictures above might scare you, but trust me this is pretty common. Cleaning isn’t the only thing though, you are probably concerned about what actually broke or caused the flood. In this case, you usually stop and consider your options. Who can help? What should I do next? You’re probably concerned about the cost of the damage too since homeowners insurance doesn’t cover all flood damages.

Any flooded basement insurance claim for water getting into the basement from outside is best taken care of by a Public Adjuster, since a lot of the times an insurance company will deny the claim. As a side note, if your basement is flooding because water is entering from outside, you should reconsider your landscaping to prevent basement flooding. The land around the basement area can act as a protector of floods. Cities like Toronto will subsidize your basement flood-proofing. So there are options depending on the location you’re in. Now let’s jump into the basics of basement flooding.

(Here’s a quick flood fun fact: The Great Flood of 1937 drastically affected the Cincinnati and Louisville areas. It left behind 14.88 inches of water in Fernbank, which is west of Cincinnati. And it left an even bigger flood in Louisville with 19.17 inches. Now that would be a disaster flood to clean up. This meme represents how I would feel about it.)

Basement Flooding Basics

If you know some basics regarding what is going on outside the foundation walls, under your foundation floor and you know some basics about your sewer you can intelligently explain to a plumbing professional what seems to be your problem or you could very well attempt to fix the problem yourself.

Let’s explain some of the characteristics of water with reference to your foundation. First water is not very susceptible to being compressed. Which means it’s going to find its way to every nook and cranny whether it be in air pocket in the ground or a crack in your basement floor or foundation walls. Water also finds its own level, meaning it could be leaking at the bottom of your foundation but find a seam in your wall and wick up 8 ft to the top of your foundation making it pretty difficult to put your finger on the problem.

So now that we know that water pressure is the root of almost all flooding and moisture problems let’s look and the different scenarios that occur to cause flooding. If a homeowner called and said “my basement is flooding” the first question should be is “is the water coming from the foundation or a floor drain?” The water is generally coming from one of those locations; a flood isn’t going to occur if you leave a window open. If it is coming from a basement floor drain the next question to be asked is “do you have an ejector pit and pump in your basement?” If the homeowner says no it tells you several things. Number one they have a gravity sewer.

Actually all sewers are gravity however this particular one is unique in the fact that all waste water, even water collected in the basement, flows under the basement floor and out to the city sewer. If water is coming up from their floor drain and they don’t have an obstruction in their sewer then the city main is backing up.

When sewers were first installed in metropolitan areas around the country they were combined sewers in that they took away both rainwater and wastewater. This comes as a surprise to some because storm and wastewater are always separated in buildings but yes in quite a few municipalities they combine together in the sewer main. Quite a few cities in the US, like Chicago or Atlanta, still use combined sewers however they are slowly being phased out. Having a combined sewer lends itself to some unique problems especially to a homeowner that is connected to it.

Basement Floods During Heavy Rain

So we bring ourselves back to flooding occurring in a home in the basement through a floor drain with no sewer obstruction. Think of a sewer in the middle of the street taking sewage from each home or business connected to it and then add to it torrential rains in the spring and fall. These combined sewers were never designed to evacuate that volume of water, in fact, typically during rainy seasons a combined sewer runs at 100% capacity. The technical term for this phenomenon is “surcharged”

When there is nowhere else for the water to go it finds its way back to each home or business connected to it and floods the homes/businesses, backing up through the floor drain and if there is enough flooding it will find its way to any crack in a foundation or wall. There are several fixes for basement floods during heavy rain, two band aids and three real solutions.

Floor Drain Plug or Econo Plug. This is just what it sounds like; it’s a plug that fits inside the floor opening for prevention. This type of plug usually consists of a neoprene rubber gasket sandwiched together by two plastic or metal plates; they are connected by a threaded screw topped off by a wing nut, as you tighten the wing nut the two plates squeeze the rubber gasket out thereby sealing your floor opening. What are the advantages you ask? It’s real cheap. The disadvantages are many.

The following is rare but possible, if there is enough pressure and the plug is tight enough the plug could dislodge itself rather violently possibly injuring someone. The other very real disadvantage is that by installing a floor drain plug you are allowing some pretty extreme water pressure to build underneath your floor. We have seen basement floors crack because of hydraulic pressure under the floor. In some instances you are better off letting the basement flood to alleviate the damage to the foundation floor. Lastly, you’ll never be able to detect a plumbing blockage in the sewer system until it’s a real problem.

Install a StandPipe. This is a pipe installed inside your floor opening that allows somewhere for the water to go in case of a back-up. What are the advantages? It’s cheap. The disadvantages are very similar to the above. Increased hydraulic pressure resulting in possibly buckling of a basement floor and if there is a sewage blockage you won’t find out until it’s a real issue, a very messy issue.

Stand Pipe

The ever popular stand pipe.

Basement Flooding Fix #1

Install a BackWater Valve. These are made by several manufacturers and they are basically heavy duty check valves. They are installed on the main sewer right at the foundation wall. As explained previously most are check valve style in that when water starts backing up into the sewer line the valve slams shut. If a homeowner chooses a manual style back water valve they have to crank the valve shut during heavy rains and remember to open it back up when the rain is over because if someone uses the facilities while the valve is closed you will have some serious backups. Advantages of having a backwater valve, they work and they work well. Disadvantages, they aren’t cheap to buy or install.

Basement Flooding Fix #2

Divorce your floor drain in your house from the house sewer. Basically you just disconnect the sewer from that floor drain tying the house sewer back in after the floor drain. This makes the whole sanitary system in the home or business a stand pipe. Advantages of doing this, again as in the above “fix” it works and the disadvantages are also price.

Basement Flooding Fix #3

The last and probably the most effective fix if it is feasible is to take your gravity sewer make it an overhead sewer. Let’s explain in a little more detail. The waste from the house now drains under the basement floor and out to the street. What you would do is abandon the old sewer, take all the fixtures in the house and tie them in over head in the basement ceiling. You would have to excavate outside dropping down to connect back to the city main at the old connection. You would then tie the basement floor drain into an ejector pit with a pump to take care of any basement fixtures or floor drains.

When the basement fixtures are used they fill up the pit and the ejector pump, pumps the waste to the overhead sewer. The advantages to this are many, usually when taking a sewer overhead you add a cleanout on the sewer as it exits the foundation this facilitates rodding if there are any future stoppages and as in the above “fit” the whole sewer system acts as a stand pipe. The disadvantage as you can already probably imagine is the cost. It’s an extensive plumbing job but one when done correctly can really give you some peace of mind.

Basement Flooding Fix #4

This is a little different angle. This fix has everything to do with the outside of the house. I’m going to give you an example that I myself have experienced first hand. I lived in a home where my back yard back up against the street behind me. There were no houses in back of mine. The street was probably 2 1/2 ft higher than the top of my foundation. When it rained heavily the run off from the street would drain into my backyard. There was nothing stopping the water from accumulating around my foundation and we had flooding issues from day 1. There are many different ways to tackle this issue but the one that would work the best is to change the grade of the backyard to take the water away from the house. The first step is to build a berm at the back of the property to shield the backyard to some degree. The next step is to have a landscaper come in and grade the backyard sloping the grade away from the house to the berm. Where the berm and grading meet you install a french drain 24″ down with perforated drain tile and a bed of pea gravel. This will allow the water to collect under the grass so you don’t end up with a pond in your backyard. Understand that if you have a situation like this there is no inexpensive fix. You can also install drain tile next to the foundation in lieu of building a berm and regrading but this fix will not keep the water from running info the backyard it will only partially protect your basement from flooding. If the drain tile becomes overwhelmed you’ll still flood. Regrading is a permanent fix to a complex problem.

Basement Flooding Fix #5 This One Needs A Story

Bottom Line, Basement Flooding Sucks

If you’ve read this site over the years you’ll notice there are many articles about basement flooding. Never did I think I’d be writing an article about my own flooded basement. It’s a bit embarrassing actually made more so by the fact that it’s been a real bear to figure it out. What I hope to convey to my readers is that basement flooding can be difficult to figure out no matter how seasoned you are.

The Beginning: First Flood

When we moved into our house it was completely gutted and rehabbed and the basement was finished before we moved in. A basement bathroom was built and the floor was tiled. The rest of the basement was carpeted. There were two low spots that I believed to be floor drains however, they were carpeted over. Since we moved into the house in late winter we would soon find out how the house handled a good rain. Unfortunately we found out pretty quick. During a nasty downpour in early spring I got the dreaded “wet carpet in basement, It’s flooding Sean” text from my wife. So I rushed home to find the carpet soaked in both low spots. I cut the carpeting back to confirm what I suspected, two floor drains both backing up. I had easy access to the clean-out on the waste stack so I got my hands on a Rigid K-1500 and opened up the sewer. The water went down and all seemed well that is until the next heavy rain. Once again I was out and about, and my wife texted me “water in basement again, come home”. So run home I did with the rodder in tow. Once again I punched through the blockage and the water drained. Of course I broke out the wet/dry vacuum, dehumidifier, fans and portable heater to dry out the carpeting.

picture of cast iron wye with cleanout

Because of the age of the house and the proximity of several large trees I suspected I had a tree root issue. There were several lingering issues that had to be addressed before the flooding could be resolved. I had an accessible clean-out that dropped straight down into the house sewer however, the fitting used was not a long sweep fitting so the only head I could use to unblock the line was a spade head. Had a long sweep fitting been used we could have gradually opened up the sewer with a tree root cutting head. Would it have fixed the problem for good? No, however it would have bought us some time.

Ridgid Sea Snake

Next Step Sewer Video Inspection

Because there was no plumbing cleanout in the yard we had two choices; run a sewer camera up the line from the street or attempt to put the camera in the cleanout from the house. Luckily the sewer camera head was able to make the turn and we were able to assess the problem. From what we found we had two serious issues:

One was that fact that we had a ton of tree roots and there was really no way to get to them unless we came in from the street

Two was that the storm sewer was criminally undersized. Even during a moderate rain the storm sewer would run almost full. Translation: Even if we cleared the tree roots out we would still back up anytime we had a downpour.

Installing a Forced Main Is the Cadillac of Flood Control

The most extensive and expensive option would be to install a forced main flood control system. The first option gives you access to the sewer for tree root maintenance and for a possible blockage but does nothing to stop the water in the case of a surcharged city sewer. The second option gives you ease of access for maintenance purposes and a heavy-duty backwater valve to stop any water from backing up into your house. However, what happens when the check valve engages for an extended period of time during a long downpour? You can’t use the plumbing in your house. If you flush a toilet the wastewater is hitting a closed check valve, if you try washing clothes, using a dishwasher, etc. you will back up at the lowest fixture in the house. If you have a basement shower with a gravity sewer it’s coming up at that fixture. A forced main sewer is the answer. Some call this a sewer lift station but it’s really not. Let me explain the system:

  • An excavation is made at a predetermined location where your sewer exits the house. You try to take landscaping and tree location into consideration when digging.
  • After exposing the sewer line and expanding the excavation to accommodate a concrete manhole the aforementioned manhole is notched or cored for the sewer piping and the manhole is lowered into place. Here’s where the magic happens. The sewer is repiped with a sanitary tee turned to 10 or 2 o’clock. (stay with me I’ll explain in a second) A backwater valve is installed on the outlet side of the tee, a fitting reduced to 2” is installed on the outlet side of the back water valve and that is connected in-line with a short piece of pipe where it leaves the manhole.
  •  We are just going to concentrate on the plumbing in the manhole for now. An ejector pump is installed at the bottom of the pit and it is piped with a check valve over to the reduced fitting on the outlet side of the backwater valve.
  • Lets move outside the manhole. You install a cleanout outside the manhole and connect it to the small piece of pipe exiting the manhole.
  • Now you backfill with new trench backfill that conforms with all local and state codes.
Picture of a forced main flood control system

So how does it all work? You have the cleanout so you can maintain the sewer in case of a backup from outlet side of the cleanout to the street. You have an opening inside the manhole so you can rod, hydro jet or camera from the manhole into the house and you have a backwater check valve in case of a surcharged city sewer. But what happens if the city sewer backs up and you are also using shower, toilet, dishwasher, clothes washer or any other plumbing fixture with a waste outlet? You’ve got a wastewater Mexican standoff. Wastewater is trying to leave the property but the check valve is shut because of the surcharged sewer. Remember that open tee fitting I wrote about above? In this particular case that open fitting would allow the wastewater to pour out into the pit so there is no potential backup in the house. Once the water level is high enough he ejector pump would cycle forcing the water on the city side of the check valve hence the name “forced main.” Once the flood control system was installed we had no more issues with sewer backups of any kind.

You could install an overhead sewer however in my case our foundation sits 2ft above the ground not allowing for much depth to bury the sewer line. An overhead sewer also doesn’t address fixture usage in the house in case of a city sewer backup.

Time Passes Basement Floods Again: The Mystery Continues

Everything was fantastic for some time. No heart palpitations when it rained, no water. Then slowly water started to accumulate back at the now concrete covered floor drain. I started to see a pattern and it was after we used the shower. But every time I ran the shower to watch if water reached the low spot none would show up. This isn’t completely unusual because there are instances where showers leak only when a person is using them due to the base flexing because of the weight. But again it was ambiguous and difficult to trouble shoot.

And then we had series of torrential rain over the course of 48 hours. I was in my office and I heard my son call for me rather sheepishly “Dad” “Yeah buddy what do you need?” “Um its flooding” “Ok how bad?” “Pretty bad, I think you need to see it” I walked out the door to see a quickly spreading pool of water maybe 8ft by 10ft 2” deep in the center. Because the basement is daily living space and my office is also located there I immediately sprint up the stairs to get towels and fans and a shop vac to attempt to control the flood.

There were a couple good things to come out of this basement flooding. One, I was determined to figure this out and two I could see water coming up through the tiles in the bathroom and running from the back of the bathroom to the low spot. This gave me a clue as to the source of the flooding. It had to be coming from the foundation. Because there were several cracks that were repaired in the basement I never thought there would be another but I went outside to look at the foundation and estimated were the water was coming from and after digging down about 6” I found a crack and a patch.

At least I had a place to start however, this still didn’t take away the nagging feeling I had about the leaking shower. Finally I pulled back the carpet and ran the shower for about 15 minutes, sure enough water began running inside the wall right back to our now infamous low spot.

Now we knew we had not one but two leaks that were independent of one another but the water from each ended up in the same place. When doing work at another person’s home it’s usually pretty fun to tear things apart however, when it’s your own house not so much but demolition had to be done.

First we tore out the drywall covering the foundation wall to reveal as expected a pretty sizeable crack that was patched however the epoxy covering the crack began to peel. I brought in a foundation-sealing expert and after he removed all of the epoxy patching he determined that the sealant probably didn’t go all the way through the crack. We set up a time to do it right.

On to that pain in the butt shower. After taking off the base board trim I could see that floor was open underneath the shower and the base was built on 2x4s to raise it off the ground a bit. I could see the shower drain piped into the ground but I couldn’t see beyond that. I turned the shower on and within seconds water began backing up from around the shower drain piping and it began running under the shower base and along the wall. Although I wasn’t sure why it was backing up yet at least I knew for sure there was a leak.

The next step was to uncover the connection and luckily for me that wasn’t too difficult. After breaking up some of the concrete right outside the shower and digging a bit I found an old floor drain. The plumber that piped the shower drain, piped it into the old floor drain with epoxy. (Code approved? NOT!) Although that is pretty shoddy plumbing what’s worse is that the waste piping serving the floor drain wasn’t taking any water.

Excavation to Uncover the Waste Piping

I had to do quite a bit of excavation to finally uncover the waste line servicing the floor drain. Once excavated I cut out a section of piping to find that it was 100% blocked with 20 years of black sediment. This floor drain hadn’t been functional in decades. I ended up cutting out all of the 2” piping until it became 4”. I ran our garden hose into the line to make sure it was clear and I visually inspected it as well. I subsequently re-piped the shower correctly with PVC, tested it, back filled it with pea gravel and some spoils and cemented over. We brought in a contractor to do the drywall, tile, painting and carpentry.

Would I call this endeavor a success? I suppose, one that took me 9 months to truly figure out. The reason I wanted to share this story with you especially in such detail is because I wanted you to know how difficult it is at times to track down basement flooding issues. I think of myself as an expert in this area of plumbing and it was still very difficult to pin down. I literally had three separate water issues manifesting in the same spot for three separate reasons. I’m lucky I still have hair because I pulled out some of it while trying to figure it out. If you bring a plumbing or basement leak professional out to your home give them the time to go over all the possibilities because as you’ve read above there are quite a few of them.

How to Deal with a High Water Table

The next section of this topic has everything to do with hydraulic pressure against your foundation floor and walls. There are some areas in the country/world where the water table never gets high enough for there to be flooding issues if you live in one of these areas good for you if you don’t read on.

We’ve talked a little bit about water pressure and how it affects your foundation, if you are having flooding problems in a basement or crawlspace and you don’t have a sump pit and pump you don’t have a drain tile system in your house. Most homes with basements are supplied with drain tile systems on the inside of the foundation under the basement floor. When it rains water is collected into the drain tile and the water flows to the pit and it’s evacuated by the sump pump. This kind of drain tile system is an acceptable way to take water away from a home’s foundation.

Let’s start from the obvious, if you have a sump pump in your basement and you are flooding and your sump pump isn’t working have it replaced. If you’re not sure it’s working unplug it for ten seconds and plug it back in, all pumps should cycle, if it doesn’t, you’re going to have to replace your pump. If the pump is working and evacuating water from the pit and the foundation is still taking water there could be multitude of issues.

The first thing to check is to see if the drain tile is collapsed. The collapse would still allow water into the pit but any water before the collapse would find its way into the house. If the drain tile is found to be intact then it is likely that the amount of water is too much for your interior drain tile to handle. One solution to this would be to install a second drain tile system on the exterior of the foundation tying it back to the existing sump pit or installing a second pit. This can be an expensive fix but sometimes it’s necessary.

Emergency Flooded Basement, What To Do First

Here are the steps you should take if you come home or walk downstairs to a flooded basement. We have several acquaintances that sleep with one eye and one ear open during thunderstorms. Although waking up to a wet basement is never very fun. Having a plan of attack in the event it happens can mean the difference between minor damage and a major restoration.

First Step to Take

Sometimes it’s easy to figure out why the basement flooded if your power has been out for several hours. The water table is super high and you’re sump pump isn’t pumping so the basement floods. This one is easy, if you don’t have a battery back sump pump or a standby generator you grab a cocktail and wait till the power comes back on. If you’ve got some sandbags ready or you have a family the size of the Duggars and a garage full of buckets you can get to work but most of us don’t.

If the power is on you have to determine the cause of the basement flooding. Go outside and take a peek at the discharge piping from your sump pump. It should be piped independently outside to a retention area or to the municipal storm sewer. You should be able to see water pumping out right away. If the pump is removing water your existing pump is being overwhelmed.

Get the Water Out As Quickly As Possible

The first thing you need to do is get the water out as quickly as possible. The longer the water sits in your basement the greater the chance you have of developing mold. So if you have power and your sump pump is actually pumping water you need to get other temporary pumps with discharge piping helping the cause. You want to make sure the flooding has completely stopped so you can move on to the next step.

**Caution** as with any situation where you are dealing with water and the possible contact with electricity please take special care. We would recommend calling a professional if the water is over 2″ in depth across the entire basement.

The Water is Out, What’s Next?

So the pumps helped with the water removal now what? If you have carpet in the basement tear it out and throw it away because it will get musty. The smell of the mold forming is something you’re going to want to avoid. There is no way to dry it in time to save it from being a petri dish for basement mold smells. Now you have to dry the floor, and any walls. Fans won’t cut it, manually drying it is your best bet. Find your local tool rental company and rent a torpedo heater or a couple and turn them on full blast until the basement is dry. There are many different companies you can purchase a heater from, just make sure the heater isn’t too hot, you don’t want it to overheat the area.

Maters Torpedo

A Couple of these will dry things out quickly

What if The Basement Was Finished?

The basement was finished with flooring and clean drywall right? We told you what you should do with the flooring or carpeting. So that leaves you with a drywall problem. You can’t dry the walls quick enough to prevent water damage and subsequent mold. The standard procedure for flooded basement drywall is to remove the baseboard and the first two feet of drywall. We agree with this procedure unless the water has been lying stagnant for some time. If that is the case all of it has to come out. Trust me, I’ve been in your shoes before, and it’s not a fun process, but it’s necessary.

Again the above can all be done by a professional plumbing contractor in conjunction with a restoration company but some of the steps can be done by you the homeowner.  As always thank you for reading and we hope it helps in the event of basement flooding.

I always tell people if you’re going to spend a significant amount of money finishing your basement spend 10% on a real flood control system. If it costs you 50K on the basement spend 5K on flood control.

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