How do I know if I need a French drain system?
4 conditions that will determine you will need a French drain
Water seeping in your basement; 1. Between the basement floor and foundation wall seam,- 2. Through a crack in the basement floor.- 3. Around lolly columns. 4. If your foundation walls are constructed of cement /cinder block, brick or field stone and your walls are leaking, you will most likely need a French drain system installed.
Solid cement foundation wall leaks can be repaired from interior or exterior. (see foundation repair)
A French drain system consists of perforated piping installed around the perimeter of a basement (Either under basement slab or around the exterior of foundations footing) and backfilled with clean crushed stone. Flexible piping with small slits is prone to clog with minerals, silt or iron bacteria so this type of piping should be avoided. When using PVC piping, holes should always be facing upward. Silt, minerals and iron bacteria accumulate at the bottom of a French drain trench. Holes facing downward will clog or contaminate the pipes interior causing the French Drain system to fail prematurely. Water does not have to raise to the level of the holes to start draining. Water will flow through the gravel that is placed around the pipe. If there is an abundance of water, it will then filter through the gravel and enter the holes of the piping. This way the pipe will always remain free of silt and other contaminates. Only a clean drain system will last a lifetime!!! When soil conditions are unstable and an abundance of mud or silt is present, proper drainage fabrics should be used prior to pipe installation to prevent piping from clogging. If the foundation is constructed of block, one, ½ inch hole should be drilled in every bottom block near the floor level. Piping is then back filled with clean ¾” blue stone or washed gravel. A plastic cove base drain is set against the foundation wall, then 2 ½ inches of concrete is then poured on top of the gravel to complete the system. The cove base will provide a small space between the floor and wall which will direct water downward from the holes that were previously drilled into the bottom block. If a foundation crack develops down the road, the water seepage from the crack will also be directed down behind the cove base thus keeping the floor dry. The French drain system should terminate at a sump pit with an adequate sump pump to handle a maximum amount of water flow.
- Hydrostatic Pressure/High Water Table
This is when rain water saturates the ground and water levels within the ground begin to rise. As the water reaches the bottom of a basement slab, pressure begins to form under the slab. When a water table rises above the basement floor, water pressure begins to push up creating seepage into the basement between the foundation walls and floor or through cracks in the floor and sometimes around lolly column’s. Water tables are usually higher in spring months during winter thaw or during extreme rain events. The only cure for this situation is a French drain System also known as a pressure relief system. No attempt should be made to seal up and hold back Hydrostatic water pressure.
- Interior Drain Systems
Here at basement waterproofing solutions, we offer 3 different types of French drain systems to accommodate all situations.
- Footing system– A patented rectangular shaped pipe sits on top of the footing set 4 to 6” below the floor. This system works great when there is not a consistent high water table. Ground water that seeps into the hollow sections of a block foundation or between the footing and the foundation wall is generally not a tremendous amount of water. This water will flow through the gravel and pipe and drain back into the ground under the floor. In some situations, the sump pump will run only during significant rain events (3 or more inches) In some situations a pump may never turn on.
- Basic system– Rectangle pipe set on or next to footing 6 to 8” below basement floor. This is the job most customers prefer.
- Premium system– 3 or 4” PVC piping set 8 to 12” below basement floor.
All jobs come complete with a transferable lifetime Warranty
- Exterior French Drain Systems
Generally exterior systems should only be installed in an area where a home sits up on a hill and piping can be gravity fed to a low lying area. These systems are typically found in mountainous areas. Some may view these systems to be superior to interior systems due to the fact they do not have to depend on a sump pump for the final water discharge but the exterior discharge piping is prone to clog from erosion and snow pack in the spring and winter months. Other applications for exterior French drain systems can be found in particular neighborhoods where an existing storm drain pipe has been installed. In these situations the storm drain piping must be 18 to 24 inches below the basement slab so all French drain piping can terminate into the storm drain. These storm drains should not be prone to backups and local zoning laws should be investigated prior to this type of installation. Exterior French drains are much easier installed during new construction. The cost to install an exterior drain system after the home has been completed can be 3 to 5 times the amount of an interior French drain system. In most cases, it would be near impossible to complete a full perimeter exterior system years after new construction has been completed. Front porches, patios, slab built garages and landscaping are just several obstacles to consider prior to installing an exterior French drain.
We have witnessed foundation plans for new homes with piping from an exterior French Drain System terminating to an interior sump pit/and pump. If you are having a new home built and discover this design to your foundation/basement drain system-make your architect change it.
20 to 70% additional water can flow through an exterior drain system compared to an interior. In an interior system, rain water will flow into French drain piping only from a high water table situation. Exterior drain systems will also see water flow from high water tables. Additional rain water that just seeps into the ground and flows downward up against foundation walls will also make its way into the French drain piping causing quite a bit of extra water volume to flow into your interior sump pit. Many sump pumps will not be able to handle this volume of water.
How about an exterior sump pit? They are dangerous and should be avoided. Only when no other options are available should an exterior sump be considered.
Sump Pumps for NY and NJ Homeowners
- Is your sump pump installed properly?
- Are you replacing your pump every 2 years?
Sump pumps must have a proper run cycle. If a pump is installed in a smaller sized sump pit, the pump will run for a short period of time and then shut off, then turn back on within a couple of minutes or even seconds. This type of operation can cause a pump to fail prematurely. Most pump motors will last many years and can run for hours. The pump switch is the 1st component to malfunction. If the switch is stuck on, the pump will burn out as the sump pit empties. If the switch doesn’t turn the pump on, the consequences will be obvious.
At Basement Waterproofing Solutions, the minimum size sump pit we install is 15 inches in diameter and backfilled with clean crushed stone. This creates a sufficient volume of water to give the pump an appropriate run time creating the proper on, off cycle.
Every pump installed by Basement Waterproofing Solutions is set up according to the exact water flow into a specific sump pit in each basement.