Trained Eye

 
 
 

Flushing Weeping Tiles

Question:

Hello Mr. Marantz.

I read your article on sewage in weeping tiles Sun Nov 30 th 2003. As I have never heard of a sewage smell coming from the weeping tiles after a sewage backup incident, I think the smell is coming from elsewhere. However, you say it is possible and suggest flushing the weeping tile with warm, soapy water.

Unfortunately, you do not advise how such a procedure could be completed. Can you please explain how this could be attempted by the average homeowner or does it have to be done by a professional?

Thank You

Answer:

To properly answer your question, I will first explain the function of weeping tiles and the reason that they may fill with sewage during a sewer backup in an older home. I hope this will illuminate the situation and I will also suggest a simple method for partial flushing of this system.

Weeping tile is a common term used for the drainage system for removal of excess ground water around the foundation in a home. The term comes from the original systems, used many decades ago, which were round tubes laid end to end in the soil near the footing and below the concrete basement floor slab. These tubes created a crude pipe, which connected to more tiles, below the concrete basement floor slab and terminated in the floor drain catch basin. These original tubes were made of clay and were similar in appearance to manufactured tiles. These clay tiles had a tendency to be brittle and collapse or fill with soil after many years and become ineffective. Later these tubes were constructed of concrete, and today plastic, but still retained the name.

The old tiles absorbed water from the soil through small gaps between the loosely placed sections and partially through the porous clay. With normal soil erosion and time, the tiles often became partially or totally blocked. The tiles below the floor slab often lose their proper slope to the floor drain and become less effective due to heaving in the soil below the basement floor. Many older homes have very little, if any, water draining through this system after several decades. New plastic weeping tile has small holes or perforations in the pipe, but is mostly continuous from the exterior to the floor drain or sump pit. This prevents most of the problems associated with blockage and soil movement that plagued older weeping tile.

The problem that may have occurred in the earlier reader’s home was after the main sewer backed up due to blockage by tree routes. In older homes, the weeping tiles drain into the floor drain catch basin, which is directly connected the main sewer pipe near the point that it exits the home. There is a trap at the bottom of the floor drain to prevent sewer gas from entering the home, from this main pipe. If the main drainpipe is partially blocked outside the home by tree roots, or other causes, the sewage from the bathrooms in the home may back up into the floor drain catch basin. As more waste water from the home enters the catch basin, it will begin to back up into the weeping tiles. This waste water may contain raw sewage, from the toilets in the home, which may enter the weeping tiles. This situation may go unnoticed for some time, until the weeping tile below the basement floor slab becomes full and the floor drain overflows onto the basement floor.

The waste water should quickly drain from the weeping tiles, once the main sewer is opened, but some of the raw sewage may remain behind. This may smell when the weeping tiles become damp. This may commonly occur after heavy rains or when there is high humidity in the basement. This was the suggested cause of the smell in the aforementioned e-mail. I believe that a plumber for the homeowner originally suggested this and I agree.

Flushing the weeping tile with warm soapy water is something that should be easily done by the homeowner, as long as a large source of water is available for the basement. The easiest way to attempt this cleaning is to duplicate the situation that caused the weeping tile to fill in the first place. That is to block the sewer. This is only necessary at the floor drain, as we still want the house plumbing to drain while cleaning is attempted. The simplest apparatus for blocking the floor drain is a common plunger, but other items may be used. It must be larger than the diameter than the drain at the bottom of the catch basin and have a handle long enough to stick out above the concrete floor.

Once the plunger is held firmly in place to block the drain, a hose may be hooked up to the laundry sink or washer faucet and used to fill the catch basin along with liquid soap. Enough water must be run into the catch basin to completely fill it and the weeping tile, just below the point of overflowing onto the floor. This soapy water may be left in place for a while to soak the tiles before the plunger is removed and the water allowed to drain completely. Repeating this procedure several times, followed by a clean water rinse to remove any soapy residue, should help considerably with any odours caused by foreign material in the weeping tile.

 

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