Drainage Terms to Know

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It is important to understand the terminology when it comes to discussing drainage systems. You want to be sure to take advantage of the options available to you and know what you are getting.


Typically 9″X9″ or 12″X12″ drains that are set in the ground. The top of the drain (grate) is located slightly below ground level. Surface water enters through the grate and collects in the box. A pipe is connected to the collection box below ground which directs the water away. Also referred to as Catch Basins.


A French drain and surface drain used in conjunction with each other in the same trench to remove excessive ground and surface water from around a foundation.


Sometimes act as the discharge point of a drainage system, opening easily when needed to allow water to flow freely from the pipe and away from structural foundations. The patented spring-loaded cap opens with the hydrostatic pressure of water flowing through the drain pipe, then closes as the flow diminishes.


Refers to the disposal of the water collected by a French or Surface drain.


Downspouts are usually vertical and extend down to ground level. Ideally, the water is piped to a sewer, or let into the ground through seepage. Most drainage problems come from the collection of rain water off the roof into downspouts, and oftentimes, the downspouts are conveying the water right onto the foundation.


When a liquid filters gradually through a porous surface or substance.

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This is a trench covered with gravel or rock that redirects surface and/or groundwater away from an area. A French drain has perforated hollow pipe along the bottom to capture water that seeps down through the upper gravel or rock. French drains are common drainage systems, primarily used to prevent ground water from migrating under the foundation. Ground water under a foundation can cause movement beyond seasonal norms. French drains are also used behind retaining walls to relieve hydrostatic pressure.


Surface drains consist of a series of collection boxes or catch basins and a solid pipe. The are designed to collect and transmit water that is accumulating on the surface (around a foundation.)


A grade (also called slope, incline, gradient, pitch or rise) of the area around a foundation refers to the inclination of the ground from the horizontal. Negative grade means the slope is towards the foundation. Positive grade, or sloping away from the foundation, is desirable to help prevent unwanted foundation movement.


This is a pump used to remove water that has accumulated in a water collecting sump. Sump pump systems are used when a drainage system (French or Surface) or basement waterproofing systems is unable to be discharged with gravity alone. In that case, water is channeled to a collection area known as a sump. Once the collection water reaches a certain volume a submersible pump is used to pump the water away.