Water infiltration (part 2)
The best way to control subsurface groundwater is to install some type of perimeter drain system to relieve hydrostatic pressure. The groundwater is pushed into the drain system and not into areas where it can damage carpets, walls or belongings. The water drains by gravity into a sump pit where a sump pump discharges it out of the house. There are two basic types of drain systems for wet basements. One is a perimeter above-slab gutter system installed at the base of the exterior foundation walls on top of the floor slab. It doubles as a base material for the wall. The other type of drainage system is a below slab perimeter drainage system. It requires the partial removal of the concrete floor slab and installation of drainage pipe, making it more expensive than the base gutter system. It is believed that an under-floor drainage system is better because the under-floor drains are believed to relieve the hydrostatic pressure before the water reaches the bottom of the floor slab.
Storm Water Backing Up Into Your Home
In many older houses with basements (mostly pre-1980), there is a perimeter foundation drain outside the exterior wall, at the level of the basement floor, next to the footings at the time the house was built. A pipe was usually installed from the perimeter foundation drain to the street where it was connected to the city storm sewer system.
This can become a problem as the city storm sewer system becomes too small when more development causes more rain runoff. When this happens, the rainwater in the sewer system can get so high that water flows backwards toward the house.
Usually, the installation of an interior perimeter basement drain system connected to a sump pump will take care of the problem. If it doesn’t, the (more expensive) alternative is to dig up and cap the pipe that is running from the house to the street from the perimeter foundation drain. However, this is not always possible; many times, this pipe is also draining sanitary waste from toilets and sinks in the house. If you believe you have this problem, contact an experienced contractor for advice.
Sanitary Sewer Water Backing Up Into Your Home
If the water is coming up through floor drains or sink drains in the basement, then the problem is often water backing up from the municipal sanitary sewer system. During heavy rains, combined sewer systems can become overwhelmed with water. This can cause sewer water to back up in the system and sometimes into homes.
There are other possible explanations, too. Sewer backups can be caused by individual service lines being plugged by grease, waste, tree roots, breaks in pipes or saturated ground. Sewer mains can also be plugged by vandalism or large items dropped down manholes.
This kind of flooding is an enormous problem for homeowners, as it’s largely out of your control and probably means fecal waste backing up into basements. Not only is it disgusting, but it can also be a serious health hazard.
In order to keep your individual lines clear, you can install back flow preventers that help stop sewer water from flowing backward into the house. Proper maintenance of your individual lines – for example, pouring tree root killer down your toilets once a year – can also go a long way in preventing sewage backups. Still, the problem is often out of your control.
Sewage in your basement means a major cleanup and a lot of uncertainty about future problems. If it’s something you’ve seen in your home, you’ll have to get your city government involved. At the very least, be aware of the problem and don’t leave anything valuable near your downstairs drains.
Each source has its own particularities and requires its own course of action. Find out more about your home’s drainage system by consulting a contractor or plumber.