Frozen Septic Tank

How to Un-Freeze a Frozen Septic Tank and Septic Drain Pipe

By Mark J. Donovan

About 8 years ago I had a frozen septic tank situation occur in one of my homes. The septic tank froze due to a number of factors. First, the winters are cold and hard in the particular area of the country where the home is located. Second, the home is rarely used during the winter months. Third, the tank is only covered with about 4 inches of topsoil. Fourth, though it was extremely cold there was no insulating snow on the ground. Lastly, the drain pipe that exits the house and feeds into the septic tank is only buried with about a foot of soil.

The depth of the soil over the septic tank and the drain pipe may not be much of an issue in warmer climates, but in northern climates where the frost can be up to 4 feet deep, this can be a real problem for septic tanks.

In retrospect, I shouldn’t have been surprised to have found a frozen septic tank when visiting the home.

Symptoms of a Frozen Septic Tank

It is fairly easy to determine if you have a frozen septic tank. In my case, we had just arrived at the home and started flushing toilets and even doing a load of laundry. Due to the fact that the septic system is a pump up system, the frozen septic tank wound up backing up water into the house, and in particular the lower level bathtub. As soon as I saw sewage water filling up in the tub, I immediately shut of the faucets, clothes washer and the well pump.

Using a pickaxe I was able to remove the 4 inches of topsoil from around the septic tank cover and lift the lid of the tank. As I had expected, the tank had a couple of inches of ice encrusted on its surface. I was able to chip through it with a steel pipe, and find the liquid effluent sitting just below it. I also checked to see if the septic tank baffles were encrusted with ice. Fortunately they were not.

I then went into the basement of the home, and removed the large PVC drain plug/nut to the drain pipe that exited the house. I also held a 30 gallon trash bucket underneath the PVC drain plug/nut as I knew the sewage water built up into the drain system would come pouring out, which it did. Needless to say, I got a little wet and dirty at the same time.

Unfreezing a Frozen Septic Tank

After inspecting the drain pipe, I determined that it was frozen as well.

How to un-freeze a Frozen Septic Tank.

After emptying the 30 gallon trash can of sewage water, I then placed it underneath the drain pipe and connected one end of a hose to the water heater and the other end deep into the drain pipe. I then turned on the well pump and the valve to the hot water heater. After about 10 minutes of running the hot water into the drain pipe, and catching a lot of it in the trash can, I melted a hole through the ice in the drain pipe so that water began to flow again into the septic tank.

I continued to run the hot water into the tank for about another 15 minutes to unthaw as much of the frozen septic tank pipe as possible. I also did this, to make sure the pump located in the septic tank was working correctly. I could actually hear in the drain pipe the septic tank pump turn on and pump up effluent to the leachfield.

Once I was sure the frozen septic tank was unthawed, at least to let a level where it worked again, I screwed in the large PVC drain plug and covered the septic tank with the frozen soil. In addition, I bought several bales of hay and spread about 12 inches of hay over the septic tank and the drain pipe area to provide some additional insulation.

Later on that spring I had the septic tank pumped and inspected. Fortunately there were not cracks, and the baffles and pump were not damaged.

Since my frozen septic tank experience, I installed some insulation around the drain pipe and added more topsoil over the tank and drain pipe. In addition, late each fall I have the septic tank cleaned, and cover the top of it and the drain pipe area with some hay. Many years have passed since that frozen septic tank experience and I have yet to have the situation reoccur.

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