How to Know If Your Septic Tank is Full? 8 Warning Signs

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8 Warning Signs Your Septic Tank May Be Full

If you have a septic tank, one of the questions you might have is how exactly do you know when your septic tank is full.  That is what we are going to layout in this article.

How do you know if your septic tank is full? There are several warning signs that your septic tank may be full. Here are 8 Warning Signs that your tank may be full: 

  1. Time interval from the last pumping
  2. Odor
  3. Slow Drains 
  4. Standing Water
  5. Gurgling Pipes
  6. Trouble Flushing 
  7. Disproportionately lush lawn
  8. Sewer Back-Up 

The key is to know how to spot these warning signs of a filled septic tank quickly so you can remedy it before it causes bigger and more costly issues.

 Read the remainder of this article to learn more about each of these warning signs of a septic tank this is full and needs to be emptied.


We had to install a new septic system when we moved in as part of closing on our house because the original one failed inspection, that cost $24,500, regularly pumping your system is well worth the cost.

What Does A “Full” Septic Tank Mean?

Before we go into the 8 warning signs of a full septic tank, let’s define what we mean by a full septic tank so we are on the same page.

There are three different definitions of a “full tank”

  1. Tank Filled to Normal Level: This means that your septic tank is filled to its normal level, meaning the water level is the height it was designed to hold, and the intake and outtake valve allows waste and wastewater to flow in and out of the septic tank with no issues. When a tank is pumped it will be emptied, but as it’s used it will return to the normal level of “full”
  2. Sludge Has Accumulated: When paper and waste continues to be used in a filled tank and gets trapped in the tank due to not being pumped. This sludge can’t disappear on its own and needs to be pumped. Wastewater continues to flow out the to the drainage area.
  3. Over Filled Tank: When the drainage field stops accepting water so water backs up into the overflow tank and water rises to the very top of the tank.

Want to See A Video Instead, About the 8 Warning Signs Your Septic Needs To Be Pumped

8 Warning Signs Your Septic Tank Might Be Full & Needs to Be Pumped

Let’s take a deeper look at the 8 warning signs mentioned above. So you know exactly how to spot a full septic tank that might need to be pumped.

Warning Sign #1: Time Interval Since the Last Pumping

The number 1 way of know if your septic tank might be full is simply understanding what the proper pumping interval for your septic system is. This will depend on the size of your septic tank and the number of people using it.

According to the Environmental Protection Agency, septic tanks should typically be pumped every 3 to 5 years. The exact interval will depend on several factors specific to your home, Septic tank, and usage rates. We had a new septic system installed in our new home exactly 3 years ago because it failed inspection when purchasing the home. We had it pumped out last week on the three-year anniversary. Here are the factors that will determine the proper pumping interval of your tank:

  • Household Size
  • Septic Tank Size
  • Amount of Wastewater Generated
  • The volume of Solid Waste

Above I said, we had the septic tank pumped last week on the three year anniversary of having it installed, this was probably a little early since our septic system was designed and installed for a 4 bedroom household, but my wife and I are the only ones living in the home. But still, we want to make sure we properly maintain our system to avoid more costly repairs down the road.

If you have recently moved into your home, ask the previous owners for a copy of the pumping and maintenance schedule that was performed on the tank prior to you moving in.

If you can’t determine the last time a septic tank was pumped, I would suggest getting it pumped right away, starting the proper normal pumping interval from the time you get it pumped.

So in conclusion, Septic Tanks need to be maintained like any other big purchase. Our Septic System, (Tank and New Field) Cost $24,5000 Dollars to install with Engineering, Design, and Installation. So to have it pumped regularly will prolong the life of your septic system and avoid more costly repairs.

Warning Sign #2: Odor From Your Septic

The second sign your septic tank might need to be emptied is experiencing an unpleasant odor from your septic tank or plumbing. Your Septic Tank and System should not smell, it is meant to process and dispose of your sewage and it should do it without any noticeable odor.

If you are smelling an unpleasant odor, it might be a warning sign that your septic tank is full. It is important to know that an odor can also be due to downdraft from your sewer vent pipes. To learn more about your septic tank vent pipe and if the odor could be due to a downdraft read this. 

If you have recently had your septic tank pumped and you haven’t increased usage or household size to indicate a shorter interval between pumps, then there might be a good chance that the odor is due to another cause and not necessarily a full septic tank.

Warning Sign #3: Slow Drains

Warning sign number three that your septic tank might be full is the existence of slow drains in your home. Drains should flow clearly and quickly, and if you have slow drains in your home it may indicate that your septic tank is full and needs to be emptied.

Now, this warning sign can also happen when you have other issues in with your plumbing besides just a full septic tank.  So one of the ways to try and troubleshoot your slow drains is to determine if the slow down is specific to one drain or if it occurs at multiple drains.

If one drain is slow, then it could be a clog in that specific pipe drain, but if the drains are slow throughout the house or in multiple locations, it could indicate your septic tank is full and needs to be emptied. The slow drains could be a symptom of a back up from the overfilled septic tank.

Warning Sign # 4: Standing Water

The fourth warning sign that your septic tank might need to be emptied is standing or pooling water near the base of the septic tank.  Your septic tank has pipes that run in and out of it throughout your property.

If you are experiencing water pooling around the base of your septic tank it may mean that the septic tank is full and needs to be pumped.  The access waste could be clogging the pipes and causing the pooling around your tank or in your yard.

Warning Sign # 5: Gurgling Water

Warning sign #5 that your septic tank might be full and needs to be emptied are toilets or drains with gurgling pipes.  This might be an indication that your septic tank is full. If you have gurgling sounds in your pipes, you should definitely have an expert investigate the issue.

Warning Sign #6: Trouble Flushing

Another warning sign that your septic tank might need to be emptied is trouble with your toilet. If you have trouble flushing your toilets then it might be an indication that the septic tank is full and is having trouble taking in the water when you flush.

If this is an issue you are having on multiple toilets then it might go beyond a local clog and be a sign you need to call an expert in to check it out and pump your septic tank.

Warning Sign # 7: Lush Lawn

Warning Sign # 7 that your septic tank might be full and needs to be emptied is one that might not seem very obvious if you are new to having a home with a septic system.  That warning sign is abnormally green or lush lawn above a portion or your septic system.  This can be common around the drainage field.

It’s normal for the grass above the drainage field to be a bit greener or nicer than the rest of the lawn, but an overly lush or super green lawn could mean you have an issue with your septic tank needing to be pumped.

Warning Sign #8: Sewage Back Up

The 8th sign and probably the most obvious sign your septic tank is full is sewer back up. This is probably the worst warning sign and a pretty severe indication you have a big problem that needs to be rectified right away as raw sewage can cause a health risk.

If you are starting to suspect your septic tank is backing up or see hints of sewage back up, call a septic tank professional right away.

What to do if Your Septic Tank is Full?

If you’ve read through these warning signs of a full septic tank and witnessed some of these warning signs in your home. Call a local septic company and have your septic pumped as soon as possible.

If you need to get your septic system serviced find a local professional in our state by state directory. Simply click your state below.

Visit our State Directory For Local Septic Service Providers