If you are planning to install an inground pool in your backyard, it's a good idea to make sure your basement is protected. The excavation for the inground pool, as well as the pool itself, can cause water problems in your basement, which can damage your home's foundation. Here's what you need to know about groundwater, the displacement of it in various types of soil, and what you can do to protect your basement so you can enjoy your lovely pool.
Potential Groundwater & Soil Problems
Groundwater. There are two types of groundwater: percolating water and underground streams. The most common type is called percolating water. This is rain water and snow melt, but it can also come from garden hoses and leaky pools. It moves through the soil without any definite direction or channel. Percolating water displacement can cause an increase in the hydrostatic pressure of the ground against your foundation. If this happens, it could cause your basement to flood or always feel damp.
Underground streams run through channels, similar to how streams run on the surface. If you have an underground stream on your property, excavation and installation of an inground pool could cause the stream to shift. Understandably, you'll want to avoid shifting an underground stream directly into or underneath your home's foundation. Before you dig, you'll need to speak with your storm water management office to determine if this is a possibility. If so, you may need to find an alternative location in your yard for your inground pool or go with an above ground pool instead.
Soil. The movement of the water in the ground largely depends on the type of soil. Silty, clay, and peaty soils are known to retain water. This could cause an increase in hydrostatic pressure on your foundation, especially if your pool fails and causes significant leakage. Since these types of soils hold onto water, you'll want to be sure to protect your foundation in case the pool leaks. Your excavation crew will be able to test the soil to determine what type it is. If you are doing the excavation yourself, hire an engineer to conduct a soil test.
Protection from Hydrostatic Pressure & Pool Leaks
It's a good idea to protect your foundation from hydrostatic pressure and any pool leaks. This can be accomplished in several ways.
- Install an exterior weeping tile drainage system somewhere on your property in between the pool location and your home's foundation. Typically, these are installed directly against the exterior side of foundations to protect basements from flooding, but they can be installed anywhere there is a problem or a potential problem. Basically, this is a long, deep trench with perforated piping at the bottom to direct groundwater away from the area. These trenches are filled with gravel to help direct groundwater downward and into the piping.
- Install an interior French drain in your basement. To do this, the concrete flooring running directly beside the interior sides of the foundation will need to be removed so perforated piping can be installed. The piping will direct water to a sump pump pit or a storm drain where it will be dispelled. The concrete flooring will be patched to cover the French drain. The purpose of this system is to capture any water before it reaches your basement flooring.
- Apply a waterproof membrane to the interior foundation walls. This is a must-have if your storm water management office determined that your property may see an increase in hydrostatic pressure from groundwater. Often, contractors who install French drains and exterior weeping tiles also apply waterproof membranes.
For more information on installing a French drain system, check out a site like http://www.permadrywaterproofing.com/.