Thaw a Frozen Septic Line
Late last Friday night we get to the cabin and find the toilet does not flush. Weird… it can’t be clogged, the flush was just water. Hmmm… I try running the sink and hear and see bubbles coming up through the toilet water.
Sh_t! The septic line is blocked — probably frozen! Ouch, over the years living in central Minnesota, I have heard of the nightmare that is a frozen septic system, but lucky had never yet experienced one. Until now.
Although we have owned the cabin for a few years now and never had a problem with the septic in the winter. But this year it was really cold. And, in addition to the cold, this year we have very little snow.
It was the perfect setup for frozen failure — a very cold winter, little snow cover or natural ground insulation and a relatively shallow system that we parked cars over. We made all the mistakes, and mother nature supplied the right ingredients.
Learn from our mistakes and avoid or fix the common risk factors for a frozen septic system:
Risks factors for a frozen septic system
- Septic line too shallow – line installed above or too close to frost level
- Septic line below compacted soil (driveways, paths) – tend to freeze deeper
- Snow cover inadequate or compacted – loss of insulation effect of snow
- Lack of vegetation or grass cover – vegetation acts as insulation for soil
- Infrequent use of system – use of system flushes pipes and adds heat to system
- Constant low volume water source (furnace condensation drainage, leaking faucet) – provides water to build ice without benefit of flushing system
Now what? Thaw it out!
OK, before you jump into this, seriously consider calling a professional who specializes in septic systems. The first time my system froze, I did just that. For $250 the problem was fixed in 15 minutes. So, like anything it’s risk vs. reward. If you like the idea of staying clean and warm in your home stop reading now and find the phone. If you still want to try this yourself, find some really old clothes and read on …
How to Thaw a Frozen Septic Line – Preparation
Preparation and Materials
- Time: Hours
- Cost: $50
Project Big Picture
- Locate septic holding tank.
- Open septic tank cover.
- Pass hose into septic line.
- Run warm water to thaw line.
Materials – Water Heater and Plumbing
|Item||What I used||Cost|
|Garden Hose||Ace 50 ft Heavy Duty Garden Hose||$45|
|Hose Nozzle||Ace 6 in. Brass Water Jet Hose Nozzle||$10|
|Anti Back Flow Valve||Back Flow Preventer||varies|
- Pry bar – lift cover
- Shovel – clear snow, dig out cover
- Old gloves – no explanation needed
How to Thaw a Frozen Septic Line – Step by Step
- Locate the first access cover of the septic system holding tank. Many systems have two access covers (one for the primary or “solid” compartment and the one for the secondary or “liquid” compartment). We are looking for the cover where the septic line from the house enters the holding tank (typically the cover closest to the house).
- Open access cover. This often requires a pry bar or crow bar to lift the concrete lid from the frozen ground. If the ground is frozen, take some time to trench out the dirt next to the lid.
- Gather your garden hose and nozzle. The nozzle should be longer than the diameter of the pipe (the pipe is typically 4″) to prevent the nozzle from turning in the pipe and therefore keep the stream pointing toward the blockage (Thanks to Nancy for the great tip).
- Find a water source. Ideally, you would use a source isolated from your domestic water supply, and therefore be sure the nothing from the septic systems mixes with your domestic water supply. Unfortunately, this may not be a realistic option. If you do use a source of water from your home — a hose faucet or utility faucet — use a back flow prevention valve to keep any water back flow from entering your domestic water supply.
Most professionals use one of three water sources to clear ice from a frozen septic line: steam, pressurized hot water or high pressure cold water.
I used a hose fitting connected to my hot water line from my utility room. It has the benefit of being fairly close to the septic tank and offered heated water. Hot water is not necessary, but will speed up the process of clearing the ice blockage.
- Next, locate the septic pipe coming from the house. Many will have a “T” baffle and enter the tank on the side closest to the house (supply). Here is what mine looks like:
Once you locate the line, you need to pass the hose, nozzle first, into the septic line so it is facing the blockage (heading back to the house). You may have to bend the hose slightly to get the nozzle into the septic pipe (I used a 6″ nozzle and needed to bend the hose a bit to get it in past the baffle).
- Turn on your water source and advance hose. Feed the hose into the pipe until you encounter resistance (this should be the ice blockage). Now the nozzle will be spraying water directly at the ice. As the ice melts, you will be able to continue advancing the hose until the ice has melted and you are through the blockage. Depending on the volume of waste water in the septic line behind the blockage, it should be fairly obvious when the ice has cleared. In my case a the volume of water returning into the septic tank increased dramatically and the water was soapy with white suds. If you are but not sure if the line has cleared, you can remove the hose (leave the water on until you are out of the septic line to prevent backflow) and have someone in the house run some water (with soap if it will help you identify the water) while you monitor for the waste water to flow into the septic tank.
- Remove the hose before turning off the water supply. Removing the hose prior to turning off the water supply will prevent back flow into the hose. Replace the septic cover and clean your tools and hose. To clean the outside of the garden hose, I pulled the entire length of hose through a handful of Chlorox disinfecting wipes several times and finished by pulling it through damp paper towels.
- Fix the underlying problems causing line freeze. After you have successfully thawed the frozen line, you should try to identify the underlying cause of your system freeze and make appropriate repairs. There are many excellent resources available online and I have listed a few below
Preventing A Frozen Septic Line
- Ensure adequate natural insulation over pipe run.
- Do not remove or compress snow over septic area (do not drive over or plow over septic system), snow has an r-value of 1 or more per inch of snow (12″ of snow = R12+).
- Add layer of straw (R1.5 per inch) or wood mulch (R1 per inch) over pipe run and other areas of septic system or plant grass, vegetation in bare dirt areas over septic system
- Avoid compressing dirt over septic line (cars, atvs, etc) as compressed ground freezes deeper.
- Add insulation over and around septic system / line.
- Add 2 – 4″ of rigid foam insulation around septic lines, and over holding tank with over lapping edges.
- Fix or Avoid continuous, low-flow water sources emptying into septic line.
- Fix leaking faucets, fixtures
- Avoid using system to drain furnace condensation water.
- Use the system regularly during cold months.
- Regular use flushes the system and add heat to the system
- Normal bacterial activity generates heat in holding tank.[/box]
Frozen Septic System Thaw Image Gallery
- Water Resources Center / University of Minnesota – Freezing Problems & Septic Systems