Thaw Frozen Septic Line
Thaw a Frozen Septic Line
After arriving at the cabin on a bitter January weekend last year, we found our drains were not working. The toilet would not flush, and the sinks would not drain. It didn’t take long to figure out what was going on. We had a frozen septic system.
Domestic septic systems work remarkably well, even in frigid climates. However, given the right conditions, septic lines and holding tanks can freeze.
What are those “right” conditions? Simple; cold and water.
Most septic systems avoid ice formation by the thermal protection offered by a buried system and the flushing and warming effects of routine use. Without these, systems can freeze.
In our case, our system was bound to fail. It was a very cold January with little snow cover. Our relatively shallow septic line, without the insulating benefits of snow, was almost certainly above the frost level and plenty cold to make ice.
In addition, we had not been at the cabin for some time, robbing the septic system of the beneficial warming and flushing effects of the home’s plumbing.
The system was cold; all it needed was water to form ice.
Our water source? The furnace. As it turns out, the condensate water from our furnace empties into the septic system. This continuous source of low-flow water added to our cold system readily filled our septic line with ice.
So, what could we have done to prevent this and how do we prevent it from happening again? The simple answer; keep the system warm and/or avoid introducing low-flow continuous water sources to the system.
Septic Systems Freeze For Many Reasons
Risks factors for a frozen septic system – things that make it too cold
- Septic line too shallow – line installed above or too close to frost level
- Septic line below compacted soil (driveways, paths) – compacted soils 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
Risks factors for a frozen septic system – things that allow ice to form
- 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 create ice buildup without benefit of flushing system
- Improperly pitched septic line or low spots in line travel – water cannot exit septic line completely allow it to freeze
Septic systems can have many factors leading to ice formation. Each needs to be considered and addressed to prevent future freeze ups. But, before we can address the problems, we need to de-ice the frozen septic line and re-open the system.
But, before you can address the problems, you will obviously need to thaw any ice within your lines and re-open the system.
Your septic line is frozen, now what? Easy; thaw it out!
To fix a frozen septic, you will need to thaw the ice that is blocking the system or line.
I did this myself and you likely can too. Before jumping into this, seriously consider calling a professional who specializes in clearing frozen septic systems. The first time my system froze, I did just that. For $250 the problem was fixed in 15 minutes.
Like most things in life, this project is a question of risk vs. reward. If you like the idea of staying clean and warm in your home while someone takes care of the repair, stop reading now and find the phone. But, if you would rather try this yourself, you will benefit from the process and learn more about your system, possibly helping you to improve your septic system and avoid future freeze ups.
So if you’re excited about doing 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|
|Anti Back Flow Valve||$8/td>|
- 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.
Frozen Septic System Thaw Image Gallery
- Water Resources Center / University of Minnesota – Freezing Problems & Septic Systems