I used to run scared every time I looked at a fixer upper house that had basement flooding issues due to either sanitary or storm line back ups. It seemed like an insurmountable issue to me. If the city lines are getting so full during a heavy rain or snow melt that they not only stop flowing but start pushing water pressure toward the house, there’s nothing you can do except complain to the city and hope they come up with some sort of fix right? It was only when this happened to my personal residence that I started researching solutions and found that there are not only multiple ways to deal with this sort of problem – but that most solutions are really inexpensive, usually less than $50.
Basement flooding problems have two root causes: Sanitary line back ups and storm water infiltration. Both occur during a period of very heavy rainfall which is sometimes made worse by a dramatic snow melt. So much water comes at once, that city sanitary and storm lines quickly fill up and the water has no where to go. This creates pressure and flow in the lines toward your house which will enter via the lowest opening….usually a floor drain in the basement or out of the top of your sump pump. The solution to the problem is a little different based on the cause.
In this post, we’ll look at sanitary line back up solutions. I’ll cover storm water infiltrations in my next post.
Preventing flooding from sanitary line back ups. Since sanitary lines are designed to only carry waste water away from houses, in theory they should not be effected by heavy rainfall. But in some older homes, there may not be two separate systems and all storm water winds up in the sanitary lines. I have two rental properties that were built in the late 40s where this is the case. All run off from the drain tiles (underground at the base of the foundation) and the gutters goes right into the sanitary line – there is no storm line. And many sanitary lines have cracks that have developed over the years that allow ground water to seep in. The end result is that the sanitary line fills up during a heavy rain and begins pushing water back up your house sanitary line. The picture below illustrates the result.
Notice the “Surcharge Level” which is the level the water rises to at the street. This is the key to the solution to the problem. Most people think that when sanitary lines fill up, the discharge into your basement represents the lines emptying out. But that’s not really the case – the water is only seeking to rise to the level of the water in the main lines at the street. Once it gets to that point, it will stop and not continue running out. So the solution to the problem is to allow the water to rise to the level of the street in a confined way so that it’s not trying to rise to that level throughout your entire basement.
By inserting a pipe into your basement floor drain, you give the water the ability to rise to the level of the street without flooding your basement. And only thing that matters is height, not volume. A 1 1/2″ diameter riser is just as effective as a 6″ riser assuming both are the same height. My plumber told me that in the areas that my houses are in, a riser that is 2 -3 feet tall should be sufficient to handle any back flow event. If you’ve had an issue or can see water marks on the basement walls from previous events, that’s your guide to the height needed.
Installing a Riser. The riser pictured at the left is in the basement of my house. Installation was simple. You start by installing a special fitting in the drain opening. This fitting is designed to seal the opening and allow for a piece of PVC to be inserted – General Wire S-4F Flood Guard Standpipe Model, 4-Inch, Small is an example of one of these fittings. Others are listed on my featured products page. (affiliate links). These fittings are $15 – $20 but may be difficult to find in your local building supply or hardware store, so your best bet is to order them online. In my case, I also needed a standard PVC tee (the line to the left is for my AC condensation which was running to the drain) and I installed a flexible 90 degree elbow for maintenance purposes + a cap to prevent sewer gas discharge in case the trap dries out. Total installation time was less than 30 minutes. Total cost was around $30.
The only downside to this solution is that it renders the floor drain unusable. But in my case, the only use was to handle the AC condensation runoff and I was able to accommodate that by piping it into the drain. Your basement floor drain might be used for washing machine discharge – but with a little ingenuity you should be able to pipe this in and actually provide yourself with a little more protection since the utility wash tub would extend the riser without making it unstable.
An important thing to remember is to not go overboard on height. The more PVC you put into the drain fitting, the more stress you have on the drain and with that stress comes an increased risk of failure. If you have more than one floor drain, you can install a General Wire 4F Flood Guard Float Model, 4-Inch, Small – this is a floor drain plug that will remain open until it senses pressure from the wrong direction. This will allow you to use the drain without worrying about back flow issues. But don’t install this as the only solution and be cautious. Pressure can build up behind the stopper and ultimately damage your sanitary lines.
Another solution is to install a back water or backflow valve. This involves a considerable amount of work including digging and usually a city permit. I’ll cover that solution in more detail along with storm water infiltrations in my next post….stay tuned!