How to Diagnose and Remedy Basement Flooding Problems

This is probably the most popular or unpopular if you’re a victim of flooding, topic in the plumbing world. 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? 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 these next few pages.

It’s surprising how little people understand about how and why houses flood and even more surprising is the fact that no one seems to explain it correctly or in a way that is easily understandable 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.

O.K. hopefully that gives you an idea of how water affects a foundation hydraulically in fact it is aptly named hydraulic pressure or hydrostatic pressure. (insert side view picture of a home with a basement  and show blue water putting pressure under the basement floor and against the foundation walls. Use arrows to represent pressure)

When water is present in a basement or crawlspace both the home and business owner immediately panic. 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.

However 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 smartly 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. Firstly 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.

O.K., 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?”. If it is coming from a 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 #1 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 waste water. This comes as a surprise to some because storm and waste water 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, one being Chicago, still use combined sewers however they are slowly being phased out. Having a combined sewer lends itself to some unique problems especially to a home owner that is connected to it.

O.K. 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. 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 this type of flooding, two band aids and three real solutions.

1. Band Aid – Floor Drain Plug or Econo Plug. This is just what it sounds like; it’s a plug that fits inside the floor opening. 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. This 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.
2. Band Aid – install a Stand Pipe. 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.
3. Fix – Install a Back Water 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. They come in a check valve style in that when water starts backing up into the sewer line the valve slams shut or in a manual style. If a home owner 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.
4. Fix - 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.
5. Fix – The last and probably the most affective 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.

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 have your pump replaced. 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 area to check would be 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.