In my last post, I went over an inexpensive way to eliminate basement flooding issues caused by sanitary line backups. In this post, we’ll take a look at how to stop storm water infiltration basement flooding issues.
The first thing we need to cover is the source of the water – the storm line system. Here’s a good depiction of how a house’s storm system should be set up and the difference between the storm and sanitary systems.
During a period of extraordinary rainfall, water that accumulates in the street can overwhelm storm sewer mains, making it impossible for the runoff from your house to drain properly and ultimately resulting in pressure pushing flow toward the house. When this happens, you’ll usually see it first in the form of water shooting from your sump pump. It may also cause enough pressure to push water from your drain tiles through the bottom of your basement walls. This can cause flooding even if you’ve never had any water in the basement or any kind of basement structural problem.
Even though water is shooting from the sump pump and/or coming through your basement walls, your sump pump will still be running. But unfortunately its doing nothing to help. If you look at the diagram above, you’ll understand why. The sump pump is just circulating water back through an already overloaded system.
To solve this problem, you can install a bypass in the sump pump drain line before it connects to the storm line. That way, you can give the sump pump a way to move the water out of the system instead of recirculating it. The sump pump will run continuously until the system back pressure is relieved (by the city main lines starting to flow again), but as long as its pumping water the sump pump shouldn’t be damaged. At the left is an example of how I did this. I simply cut out a piece of the PVC sump pump drain line where it was leaving the basement, installed an $8 Fernco tee (not too difficult to get it in even though the other sides are glued in place), inserted a $2 clean out and cap and bought a $10 discharge hose. By installing the discharge hose at the cleanout, I can direct water down the driveway instead of recirculating it through an already overloaded system. Total cost around $20.
The downside to the sump pump bypass system is that the homeowner or the tenant would have to be home when the storm hits or have anticipated the problem. Sometimes when storms are predicted and I won’t be home, I’ll hook up the discharge hose as a precaution. Not ideal, but provides some piece of mind. Probably not the best solution for a rental property though where you’d have to rely on the tenant to manage this process.
A better way of accomplishing what I just described is to install a 2nd back up sump pump that drains to the yard instead of recirculating back thru the system. The set up is illustrated to the right – the 2nd pump is installed higher to handle overflows. In my situation, this wasn’t practical based on where the sump pump had been installed (it was pretty much boxed in by a garage and back deck – getting the main line out was hard enough, let alone a 2nd line). If I was installing the system shown at the right, I might still put the bypass on the main line too so that if I was able to I could be discharging water out of 2 openings in the event of an emergency. Putting a 2nd pump in will probably run around $750, but worth every penny to eliminate the worry of a flooded rental or to be able to show a buyer who’s heard that there are flooding issues in the neighborhood.
Finally, the most expensive but perhaps the most effective solution is to install a backwater valve. The concept is pretty simple. The valve allows waste water to drain normally from the house, but will close if the flow starts coming from the other direction (from the sewer as shown on the left) – preventing overflow and flooding reaching the basement. This solution will work for both storm and sanitary back up problems, but professional installation is vital. Proper placement, installation and maintenance is important to assure that your storm and sanitary systems operate as they should in normal situations – don’t try to do this installation yourself! There’s always digging involved and oftentimes unexpected issues, so expect a backwater valve to cost at least $1000. However, in spite of the cost it may be the best solution for houses that have a persistent flooding issue.
There you have it. A few ways to solve basement flooding issues for less than $50 – and a few that cost in the $500 to $1000 range. None of which though that are so costly or complicated that it would cause you to walk away from a fixer upper house. The good news is that evidence of flooding in the basement will scare a lot of other investors and create opportunities for you…..just make sure you can tell the difference between flooding and water in the basement due to structural issues or leaks. That problem is entirely different cost wise…..but also not necessarily a show stopper either. I’ll cover my experiences waterproofing and rebuilding basement walls in a future post.