Preventing and resolving frozen septic tank problems in winter

Category: Winter
16 May 2022

The cold temperatures of winter pose a real threat to the residential septic system and plumbing. Failure to prepare your septic system for winter might result in freezing. Apart from the cold weather, there are several other factors that cause frozen septic tank problems in winter. In this article, we will look at some of these factors and what you can do to prevent or recover from a frozen septic tank.

The main causes of frozen septic tank problems in winter

No snow cover

If there is little or no snow cover on the tank, the tank will not be sufficiently insulated from the cold. Snow provides a blanket on the tank and drainfield areas. This insulation is very crucial in the cold of winter because it helps to retain the geothermal heat of the soil layers and that of the septic tank. If your septic tank lacks this snow cover, frost will go deeper into the soil and that might cause the tank to freeze. Do not shovel snow away from your septic tank or your drainfield area.

Compacted soil/ snow

Healthy soil is typically made up of one part of organic matter and mineral particles and one part of pore space. Pore space is what provides room for water and air to circulate in the organic matter and minerals. This provides a perfect environment for microorganisms to thrive. However, when the soil gets compacted, the particles are pressed too tightly together that there is literally no space for air and water to pass through freely. Some soil types, like clay, are naturally compacted but even those soils that are not can easily get compacted due to applying too much pressure e.g. driving heavy machinery over them. Compacting soil or snow during winter can cause the frost to sink deeper into the soil and that can result in a frozen septic tank.

Irregular use

The process of digesting organic waste by anaerobic bacteria helps to ensure the septic tank remains warm. This explains why regular use of the septic system is very important during winter. If your house or cabin will be unoccupied for a long time during winter, the septic system will not receive wastewater and that might cause septic tank problems in winter. The same may be true if there will only be one or two people in the house during winter. If you are planning to be away during winter, you can schedule for pumping before you leave to help prevent the septic tank components from freezing and bursting.

No plant cover

If the septic system is at least a year old, then you probably have planted grass over it. However, if you installed a new septic system late in fall, there is a good chance that winter will come before your grass grows. Vegetation cover also helps to provide insulation during winter and it also helps to hold the snow in place so lack of it might cause the septic tank to freeze.

Leaking showers and fixtures

Apart from wasting gallons of water, a leaking fixture can also result in other septic tank problems in winter. If a shower or one of the fixtures has a leak, it will send trickles of water down the septic system. Usually, wastewater from the house has bacteria and this is good for the septic system. However, clean water does not help in replenishing the septic tank with bacteria. This clean water will cause hydraulic overload and it will reduce the rate at which bacteria break down the organic waste. This means the heat generation will also be reduced and that can be bad for a septic tank during winter because it can make it freeze.  Additionally, the trickling water can freeze in the pipes because it is not moving fast enough. Some appliances like humidifiers and high-efficiency furnaces can also result in frozen pipes.

Waterlogged systems

If your septic system appeared waterlogged in the fall, there is a very high probability that the water that was seeping out of the side in a mound will freeze in the cold of winter and this will prevent any more effluent from passing through. To void this, use biological additives to clean out the septic system before winter sets in. These biological additives introduce billions of bacteria and enzymes into the septic system. These microbes digest the organic waste in the septic tank and that helps to unblock the system.


Maintenance tips to avoid frozen septic tank problems in winter

There are a couple of maintenance tips both before and during winter that can help your septic system to function optimally and also to avoid having to deal with the common frozen septic tank problems in winter. Most of these maintenance tips are DIY but some of them, like insulation of the tank, might require the hand of a professional. Let’s look at each of the tips in more detail below.

Winterizing plumbing pipes

Winterizing is the process of preparing your plumbing pipes for the extreme cold of winter to prevent your pipes from bursting as the water freezes and expands in the pipes. Winterizing is a very important maintenance tip if your house will not be occupied during winter. The winterizing process entails draining all water from all pipes and emptying of the water heater. Antifreeze solutions are also usually used for winterizing plumbing fixtures but you shouldn’t use antifreeze if you have a septic tank because it will affect the performance of bacteria in your septic tank. Here are the important steps to follow when winterizing your plumbing pipes.

  1. Shut off the water valve and then switch off the water heater and water pump. This is an important step because it helps to protect heating elements when there will be no more water in the tank
  2. Open all taps and drain valves. Use a checklist to ensure all of them are open. It is important to have all taps open because a closed one can create a vacuum that will hold water in the pipes. All valves and taps should remain open throughout the winter season
  3. Use an air compressor to blow out any excess water out of the pipes
  4. Open a drain valve in the hot water tank and allow it to discharge until it is completely empty. Because hot water tanks sometimes do not have floor drains, you might have to connect a garden hose.
  5. Drain all water in the holding tank and especially so the water that might be in the rubber diaphragm.
  6. Flush your toilets and use a sponge to dry out any water that might be left in the toilet tank.

Avoid snow compaction

As we have already seen, snow compaction can lead to septic tank problems in winter. Even though it is important to have snow over your septic tank, it should not be compacted. Avoid walking, driving or pushing heavy objects or machines over the septic tank because exerting any external pressure will compact the snow over the septic tank. Do not construct any structure over the septic tank for the same reasons.

Inspect the system

It is advisable to inspect the system just before winter sets in. The main purpose of this inspection is to try to locate if there are any faults in the system.  Look for cracks or any related faults and also check to ensure the septic tank is not too full. Inspect the drainfield area just to confirm that there is no surfacing effluent or spongy soil. Sometimes, a failing system is not easy to detect manually so you may want to use a more scientific approach. This is where the water tracer tablets from Bio-Sol come in handy. You flush the tablets in your toilet, given it a couple of hours and if you see the green dye on the grass the following day, the septic system if either failed or almost failing. Luckily, you can correct such a problem by adding the septic-safe biological additives. These additives will introduce billions of bacteria and enzymes into the system and they will ultimately clean up the system by digesting the organic waste.

Pump the septic system

If your septic tank is almost due for pumping, schedule a pump just before winter. If the tank gets full during winter, pumping it will be a laborious exercise and companies that do pumping in winter charge extra for the trouble. Pumping the septic tank might also help to prevent freezing of the tank if you will be away from the house the entire winter period. However, before pumping the tank, it is a good idea to try using biological additives because in most cases, that will fix the problem.

Add insulation

Placing a 12-inch layer of straw, leaves, hay or any other mulch material over the tank and pipes can help to provide some extra insulation.  You should especially do this if your septic tank is freshly installed and there is no grass over it. Otherwise, just allow grass to grow slightly taller over the septic tank and leachfield and that should be sufficient to hold snow for insulation during winter. If your tank is already frozen, do not put the mulch for insulation because it can interfere with the process of thawing when the temperatures get a little warmer. Adding some insulation materials on all exterior pipes can also help to prevent them from freezing. You may want to consult with a qualified plumber to help you know how best to go about this without dislodging pipes or harming your plumbing. The plumber might recommend replacing your pipes with special insulated ones among other important improvements.


Recovering from septic tank problems in winter is no easy task. For instance, if you need to have the tank pumped in winter, the pumping company has to worry about getting to your home in the snow, then shoveling around to locate where it is in your property before progressing to pump a tank. Then there is the possibility of finding a frozen septic tank which complicates the process even more. This is why you should take the time to prepare your plumbing and your septic tank for winter. By following the tips suggested above, the septic system will run smoothly and you won’t have to worry about the inconveniences and costs of dealing with frozen or failed systems in winter

About the author


CEO at Bio-Sol

Our goal is not only to offer you the best products on the market but also to educate and empower you with the insights you need for successful wastewater treatment.


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