Wednesday, May 4, 2005

Trench needed to solve standing water problem

By TIM CARTER
Tribune Media Services

Q. My husband and I live in a one-story home built on a slab. A few days ago I heard a bubbling noise coming from one of the floor heating vents. I looked inside the vent and there was standing water! We pumped out water for two hours, but the vents filled back up. How can we stop it? Do you think this problem was known by the previous owner and, if so, do we have any recourse? — L.F., Norcross, Ga.

A. Many people who own a slab house think they are immune to problems caused by subsurface water.

The problem is happening because water often moves sideways through soil instead of straight down.

When rainwater falls onto the ground, it readily passes through the topsoil, as this upper level of the soil frequently contains plenty of air voids. But as you go deeper into clay soils, the soil becomes extremely dense and often water is blocked from going down. The water then starts to move sideways through the soil, always flowing downhill and often popping to the surface like a spring. This water is the fuel that creates creeks, streams and rivers.

If you look outside your home and imagine the vast amount of soil that might be higher in elevation than your house, you might be amazed to learn that there are hundreds of thousands of gallons of water in the soil, much of which is moving directly toward your home. This water can easily find its way under the slab and into the ductwork beneath the slab. It is no wonder the vents filled back up after you pumped them out.

Anyone with any part of their home being invading by subsurface water can stop it in almost all cases by capturing the water outdoors and then redirecting it to the lowest part of the lot.

Think of how gutters work on the roof of a house. Gutters capture the vast amount of water on a roof and channel it to various outlet holes within the gutter, where it’s piped away from the roof. Ideally rainwater from a roof should be piped far away from a house and not be allowed to drop out of downspouts onto simple splash blocks adjacent to a foundation.

You can capture the subsurface water by digging a trench around the outside of your home. This trench should be placed about 6 feet to 8 feet away from the edge of your home. Dig this trench 6 inches wide and between 18 inches to 24 inches deep. The bottom of the trench should be parallel with the soil as it goes around your home. The trench should be extended away from the house and needs to end up at or near the lowest point of elevation on your building lot.

As the trench starts away from the house, make the bottom of the trench nearly level. As the ground falls away from the house, the trench will become shallower, and eventually the bottom of the trench will be level with the top of the soil.

Next, place a 1- or 2-inch layer of washed 1-inch-diameter gravel in the bottom of the trench and then a 4-inch-diameter perforated pipe in the trench. Fill the trench with more 1-inch washed gravel until you are within 1 or 2 inches of the top of the trench. You can place pieces of sod over the gravel.

The subsurface water will now pass through the soil and enter the trench. Because it is easier to pass through gravel instead of soil, the water will drop down to the pipe. There it will enter the pipe and be transported rapidly away from your home to the lowest part of your lot. The underside of your slab will never be saturated with water again.

If your state has a property disclosure law and the previous owners knew of this serious defect, they may have been obligated to bring this flaw to your attention. You should call the Realtor you used in the transaction to see if there was a property disclosure form that was not given to you.

You can also call your local fire department. Just about every fire department in the nation keeps very good records of each time it leaves the station and is asked to put out a fire or help in another matter. If your local department was ever called to the house to help pump out the vents,the previous owner likely knew there was a problem.