How to Properly Size a French Drain Pipe

What You'll Need
Underground pipes
Tape Measure
Channeling Area

The French drain pipe system has been popularly utilized to channel ground water from one area to another. It consists of a rock and gravel piled up as a ditch. When water seeps down into the monitor area below the ditch, pipes collect the water and channel it to another location. French drain pipe systems have been not only to transfer water flow, but also used to collect water for reservoirs. There are several variations of French drain pipe systems. Modern technology has replaced the traditional rock and gravel ditch with special drain tiles, which allow water to seep through the pipes more efficiently. The French drain pipe plays a pivotal role in preventing ground water from seeping to the building foundation. 

A building foundation immersed in ground water is a worst case scenario. Building foundations are especially vulnerable to water. Once water has penetrated a building foundation, it can render the base of a structure unstable and unsafe. Water can erode a building foundation over a period of time. Once a building foundation has been compromised, the whole structure can sink to the ground at any time because the base has been weakened by water. French drain pipe systems are common at the sides of structures, especially tall buildings built solidly on the ground. The proper size of a French drain pipe system around a certain area or structure is very important in effectively channeling any water that seeps down to the pipes. These steps will help you assess the ideal size of a French drain pipe system for your intended area or structure.

Step 1 - Determine the Measurements of the Area

By determining the measurements of the area where you will apply the French drain system, you can ascertain how many pipes you will have to prepare, and how much rock, sand and gravel you will use. The typical size of a French drain system is 6 inches wide and 12 inches deep. This drain system will have to be replicated if the area is large.

Step 2 - Determine the Amount of Water on the Area

Ground water comes from rain, so it’s important for you to know the average rainfall of an area in order to determine whether or not to dig a deeper and wider French drain system, or to install back-up pipes to compensate for strong water flow.

Step 3 - Dig the French Drain Pipe System

After wearing your gloves, use the shovel to dig an area with standard measurements mentioned earlier. Then add 1 inch of gravel to the trench before laying down the primary French drain pipe. Then situate the other pipes in a circular area around the primary pipe to serve as parallel drainage in case the primary pipe is unable to handle water. Don’t forget to attach a pipe leading to another area to the primary pipe before covering up the trench with rocks, gravel and sand. Now your French drain pipe system is ready.

Step 4 - Test the System

Test the system by pouring water on the system and checking if the water is transferred to the channeling area.