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How often should I pump my septic tank?

Updated: May 11, 2020

How to tell when your septic tank is full.

This may seem like a really simple question, so why can’t you ever get a straight answer from septic pumping companies? That’s because it’s surprisingly difficult to explain over the phone! To actually determine the level of your septic tank requires special tools and may get a little dirty, that’s why we never recommend that homeowners investigate this on their own. In this article we will do our best to give you a simple answer while explaining the details of why it’s hard to determine.

How often should your tank be pumped? The simple answer: Every 2-4 years. The more people living in the home, the more frequently your tank should be pumped.

Most people think of a septic tank like they would a glass of water, once the water reaches the top it’s “full”. However, that’s not the case with septic tanks. A septic tank typically only holds 1000-2000 gallons of water at any given time, which means that most households would “fill” the septic tank within a few weeks. This is where the Soil Treatment Area (STA) comes into action (see “How A Septic System Works” for more information). Basically, once the glass of water is “full” the water has to go somewhere. In septic tanks, there is a pipe about ¾ of the way up that the excess water “spills” into. What this means is that your septic tank is actually ALWAYS full of water. This is what we call “normal operating level”.

So what actually determines when your septic tank is full?

A “full septic tank” is actually determined by the number of Total Suspended Solids (TSS). When wastewater enters the septic tank, the solids fall to the bottom of the tank. Over time those particles breakdown, and some will suspend in the water above the other solids. The more solids there are in the tank, the more Total Suspended Solids there are. This can create a problem for your STA since you want only the cleanest water possible in your leach field.

The simple answer is this: the more solids there are in your tank the fuller it is.

Since there is always water above the solids it can be tricky to determine exactly how full your septic tank actually is. There are special tools with really epic names like “The Sludge Judge” that are used to determine exactly how full your tank is. John Todd Companies has these tools, but rather than sending someone to your house every so often to determine when your septic tank is ready, there is an easier option.

One method used in determining when your system is ready to be pumped is the number of years since your last septic pumping. So how many years should you go without septic pumping? That’s another tricky question! The answer will be different for every home, and may be different depending on what season of life you’re in. Since the septic system treats ALL of the water from your house, the number of years in between septic pumpings really depends on the kind of water usage in your house.

Typically, there is some guess work in determining how much water your specific household uses. It’s not only determined by HOW MUCH water and wastewater you use, but also the TYPE of wastewater that is used (read “Healthy Habits for Septic Systems” for more information). A general rule of thumb is that you should pump your septic tank every 2-4 years. In the State of Colorado, the health department actually requires a MINIMUM of 4 years between each septic pumping. Once your septic tank has been pumped once or twice, the technician should be able to advise whether or not you need to shorten or lengthen the time frame between each service.

So, should you pump your septic tank every 2 years or every 4 years?

The first trick we use to get you a starting point for septic pumping frequency is the number of people living in your home. If it is just two to three people on a daily basis, we recommend getting your septic tank pumped every four years since the usage will be low. However, if you are putting a lot of fats, oils, grease, food scraps, or even non-septic system approved toilet paper, you will need to get your septic tank pumped more often.

For homes with three to four people we recommend getting pumped every three years, and for homes with more than four people we recommend getting pumped every two years.

Other things to consider are how many parties or social events you have in your home. This can put a lot of wear on your leach field since it is a large increase the amount of water used, and wastewater doesn’t get as much pre-treatment time before going to into the STA. If you have frequent parties or are planning on having a large event at your home, it may be worth pumping more often or even right before the large event. Also, if your property is a rental property, your guests will not understand how to properly use a septic system. This means they will flush the wrong things and cause undo wear on your septic system. If you have an RV dump station at your home (not recommended) then it is better to have your tank pumped more often. The chemicals in an RV typically kill good bacteria in your septic tank and should be avoided if possible.

Other things that affect how often you should pump:

· Large or frequent social events (parties, weddings, etc.)

· Long term guests

· Vacation homes (don’t need pumped as often since you will not be living there)

· Rental properties

o Ski rental properties are known for having large numbers of guests all winter long (sometimes 10-12 people in a 3 bedroom home). This requires much more frequent pumping)

o You should track the number of guests that stay at your rental property and understand that a lot of them probably do not know the “do’s and don’ts” of a septic system.

o You can download a PDF of our “Healthy Habits for Septic Systems” here, it may be useful to print and laminate this page for your guests.

· RV Dumping Stations (on your property)


In summary, a septic tank is not “full” when the water is at the top. That is considered “normal operating level”. A septic tank is considered full when the solids build up in the bottom of the tank, and since this is very difficult to determine without the proper tools there are tricks to determining when your septic tank is ready to be pumped.

· Normal residential properties’ septic systems are pumped every 2-4 years.

· Colorado Health Departments require a septic pumping every 4 years minimum.

· The more people in your home, the more frequently you should be pumped.

· The worse stuff you put down the drain, the more frequently you should be pumped.

- Also see “How a Septic System Works” here.

· Consider what your property is being used for (rental, vacation, RV dumping)

We hope this helped you understand the strangely-difficult-to-answer question of how often to pump your septic tank! Check out our other articles below so that you can better understand how to protect one of the largest investments in your home: your septic system!

Jesse Todd

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