Water management strategies that help remove excess water from the foundation often include the use of a reservoir called a sump. The sump is generally a small pit (crock or vault) that extends through the foundation into the ground below and provides a drainage place for excess water. A pump is used to convey the water out of the sump and discharge it away from the exterior of the house. While sump pumps are very effective in removing water, if they are not covered and installed properly, they can create additional water management issues, as well as indoor air quality concerns for the house.
Uncovered or improperly sealed sump pumps can allow water vapor and pollutants such as radon and other soil gases to enter the interior of the home. Without an effective cover, these pollutants can enter basements and crawlspaces and then mix with the air inside the home (EPA 2012).
Figure 1 - An open sump pump can allow unwanted moisture into the basement. The opening is also a source for radon to enter the home.
Sumps, Pumps, and Covers
Sump pumps must be covered or they will be a source for introducing moisture into the home. Sumps usually have standing water, and when that water evaporates into the air, it raises the relative humidity inside the home. High relative humidity leads to higher moisture content of wood framing, which can lead to fungal decay. From an air quality perspective, water that wets susceptible building materials and furnishings can also promote the growth of mold that can make the home's occupants sick. Moist environments also provide an attractive environment for pests.
Sump pump covers are often loose and do not form a tight seal. A mechanically attached sump pump cover reduces the possibility of moisture and pollutant introduction into the home.
Follow these steps when installing a sump pump cover:
Install the electric sump pump to manufacturer's specifications, making sure the float is unobstructed. Installation of the pump should happen after the home's electric meter has been set; this will allow you to test the pump and ensure it is operating properly and discharging water as intended.
Install a sump pump cover that is tight fitting and that seals the entire surface of the crock or vault. Sump covers should be made of durable plastic or other rigid material and designed for air-tight sealing with a built-in gasket. Select a sump pump with a lid that has built-in air-sealing grommets around all penetrations for electrical wiring, water ejection pipes, or radon vent pipes.
Mechanically fasten the cover in place with screws or other means that will maintain tight contact between the lid, the gasket, and the rim of the crock. Sump covers that permit observation of conditions in the sump pit are recommended. If the sump is installed in a concrete slab, caulk around the outside edge of the vault where the vault meets the concrete (EPA 1994
). If the sump is installed in a crawlspace with a dirt floor covered by a polyethylene vapor barrier, ensure that polyethylene covers the ground around the sump pump and is taped to the rim of the vault.
Figure 2 - Properly sealed sump pump. The sump pump above is properly sealed with a mechanically fastened gasket.
Figure 3 - Sump pump functions. The image above shows the components that make up a successful sump pump installation.
Radon is a naturally occurring radioactive gas found in the soil and air. It can be drawn into a building and can accumulate to high levels. When radon enters a home, it decays into radioactive particles that are attracted to particles in the air, which occupants then breathe in. Radon is a proven carcinogen. The radon particles further decay, releasing bursts of energy which can cause damage and, in some cases, the potential for cancer (EPA 2001).