How often should I pump my septic tank?

adminSeptic Maintenance

It’s a question that pops up repeatedly: How often should I pump my septic tank? As a co-owner of Western Septic & Excavation, a company that pumps septic tanks, it’s a question I, and my partners, answer multiple times a week.

The short answer: no one knows.

How did we, as professionals devoted to the task of safely disposing of wastewater from rural residences and businesses, come into this fascinating tidbit of knowledge? Stay tuned while I explain. This could get boring, so grab a diet soda and a fistful Cheetos to pass the time.

Let’s start with a basic question that many people can’t answer.

How often should I pump my septic tank?

Septic tank pumping in Twin Falls

Why do I need to pump my septic tank?

Old-school thinkers often suggest that a septic tank doesn’t need to be pumped if it is working correctly. Ever. We can assume this is true as long as we also conclude that very few, if any, septic tanks work “correctly”. While this level of septic utopia may be theoretically possible, in real life it virtually impossible to attain. Rather than take the long way around, it’s much easier to accept the overwhelming evidence and come strait to the conclusion that septic tanks need to be pumped periodically in order to prolong the life of the system. The fact is, there are too many factors that affect the system for it to work textbook perfectly all of the time. Hence, it must be maintained.

The purpose of the septic tank is two-fold; first, it holds wastewater for an extended period of time to allow time for bacteria to break down and digest solids in the wastewater. Second, it stores solids that are not digested for future removal via pumping. That’s right, in nearly every septic tank there is a certain accumulation of solids that are either very slow to break down, or do not break down at all. Over time, these solids add up in two layers within the tank. Floating on top of the liquid in the tank is a layer of solids known as scum that is lighter than water, such as fats, oils and greases. Settled on the bottom is another accumulated layer, called sludge. Of course, when you mention the term “septic sludge” everyone’s mind always jumps straight to the ickiest of the ickies, but trust me, there’s a lot more involved. A wide variety of substances, from coffee grounds to baby wipes, from feminine products to candy wrappers flushed by kids who were hiding evidence, settle out down there, and there they stay, until a septic pumper comes along to remove them.

So what happens if I, as a homeowner, neglect to pump my septic tank? Eventually, these accumulated layers of floating and settled solids begin to take up a substantial amount of space within the tank. As that happens, the usable holding capacity of the tank is drastically reduced. Wastewater within the tank is held for a much shorter time before it is forced out to the drain field by incoming flow. This gives the bacteria less time to digest solids, and, in a one-two assault on your drain field, also allows less time for undigested solids to separate into their appropriate layers. The result is an ever-increasing amount of solids, still suspended in the wastewater, flowing to the drainfield. Once there, these solids settle out of the wastewater, clogging pipes and forming a thick layer of sludge, called a biomat, that reduces the ability of the water to infiltrate into the soil. While a small biomat is useful and aids in the treatment of the waste, if the biomat gets too thick the wastewater flow will eventually outrun the ability of the drainfield to absorb water, and the system will back up. Another common issue that is caused by a lack of septic pumping is that the floating scum layer gets too thick and actually blocks the pipe coming into the septic tank, causing a clog that results in sewage backing up in the home. In a nutshell, failing to pump my septic tank can eventually cause sewage to back up into my house and / or ruin my drainfield. Clear enough?

As a footnote, I would add that a lot of people who have us pump their tanks ask us afterwards if the tank was “full.” Let’s be clear here: a septic tank is always full, and should be. After pumping, the tank will usually fill with liquid waste within a week. This is normal. It is the solids that have settled to the bottom and have floated to the top that we are concerned with. However, we can’t get the solids without taking the liquid as well, so we mix and pump the entire contents of the tank. If a pumper ever mentions that the tank is “full”, he is probably referring to a solids accumulation that would make pumping the tank a priority.

Now that we’ve gone over the reasons why I need to pump my septic tank, let’s move on to…

How often do you recommend I pump my septic tank?

Whenever someone poses this question to me, I always refer to the recommendations of the Health District. They, along with the Department of Environmental Quality and the EPA, advise using one of two methods to determine when or how often to pump a septic tank. The first method involves measuring the thickness of the scum and sludge layers, and pumping the tank when the volume of the solids exceeds about 25%-35% of the total volume of the tank. There are various ways to measure these layers, the preferred method being an actual sampling tool designed specifically for sampling septic tanks. If a sampling tool isn’t available, there are also ways to measure scum and sludge using a homemade device. While sampling and measuring of solids is the scientifically preferred method of determining whether a septic tank needs to be pumped, septic tank sampling is nevertheless an imperfect science, even if done using proper equipment. If the solids distributed themselves evenly throughout the tank it would be fairly simple to calculate, but that usually isn’t the case. Sludge and scum tend to accumulate at a much faster rate at the inlet end of the tank. Depending on where the sample is taken, for example at the inlet, middle, or outlet end of the tank, the accuracy of the sample used to calculate the volume of the solids will vary widely. While some tanks have a large access lid on the inlet end, which is ideal, many older septic tanks have no access whatsoever at the inlet end of the tank. A lot of these older tanks and even some modern tanks have the main access lid in the center or even at the outlet end of the tank. Measuring the solids levels at these locations will not give a clear picture of the solids accumulation at the inlet end of the tank. The scum layer will at times be very heavy at the inlet end of the tank and almost nonexistent at the outlet end. As I mentioned earlier, a heavy scum layer near the inlet can build up to the point that it clogs the inlet and causes a sewage backup in the home. In those cases, a heavy scum accumulation around the inlet will become problematic long before the volume of settled solids reaches the recommended volume of 25%-35% that would warrant pumping the tank. It would be in the owner’s best interest to have the tank pumped at that point to remove the excessively thick scum layer in order to reduce the chance of a blockage that would cause an unpleasant sewage backup.

The second recommended method I can use to determine when to pump my septic tank is to establish a regular schedule for pumping based on calendar years. Environmental health experts agree that, as a general rule of thumb, a homeowner should pump his septic tank every 3-5 years for an average family of four. However, even this recommendation is very subjective. Every household is unique. Peoples’ habits vary widely from family to family. Some nationalities eat a lot of fried foods. Oils from frying enter the septic system from dish washing and through body wastes. Some folks use scented Kleenex as opposed to the plain variety. The perfumes and dyes in these products have been known to affect bacterial populations within a septic tank. A meticulous housekeeper will send more detergents down the drain from laundry and house cleaning than the average person would. A foodie who enjoys baking often unknowingly puts a lot of oils into the drain. How? Every batch of chocolate chip cookies was baked in a pan that was greased with shortening. That pan was then washed. Some people are very concerned about germs and viruses. These people often insist on using antibacterial hand soaps and use a lot of disinfectants in their cleaning regimen. Antibacterial agents and disinfectants are harmful to the bacteria in the septic system. To further complicate the matter, some strong prescription medications, such as chemotherapy drugs, enter the system through body wastes and can harm the ecosystem within the septic tank and drainfield. In some cases, septic systems are actually ruined by residents who use recreational drugs. All of these things, and many more, contribute to the accumulation of solids that forms in the tank by one of two means; either by directly disposing of fats, oils, and greases, and other solids into the system, or by harming the bacteria that are tasked with processing these substances. Therefore, some households will accumulate solids at a much faster rate than others, even with the same number of people and a seemingly similar lifestyle.

Then there is water usage. A moderately wealthy elderly grandmother may live by herself in a large home with a septic system that is designed to accommodate six people, while a struggling family of six might be sharing a small home that should only house three or four people. A family with very young children won’t use nearly the amount of water as a family of the same size whose children are teenagers, in high school, active in sports, who shower two or three times a day. Even income levels can affect water usage, since owners of large “trophy homes” might install six shower sprays in their shower, while homeowners of the middle class would usually be content with one head in their shower.

We can see how, with the many variables that affect the septic system, it is nearly impossible to come to a solid conclusion on how often I should pump my septic tank. We cannot even guess how fast the solids will accumulate. I’ll use myself as an example. As a septic professional, even I wasn’t sure how often I should pump my septic tank. When I finally decided to pump it, I honestly didn’t know what the solids accumulation would look like until I opened the lid. Thankfully, my septic tank appeared to be working well and wasn’t overly full of solids, but the fact of the matter is that I didn’t know until I opened the lid. We have seen septic tanks that had very heavy solids accumulation only months after having been pumped, while on another occasion I pumped a tank for an elderly man that hadn’t had his tank pumped in over 15 years. His tank could have been mistaken for a nearly brand new one. It had virtually no solids whatsoever. His was definitely the exception to the rule, however, and nobody who understands septic systems would recommend waiting that long to maintain your system.

Is there a way to find out how often I should pump my septic tank?

When should I pump my septic tank?

Pumping a septic tank in Twin Falls

Yes. Thankfully, there is a way to stay abreast of septic maintenance. I recommend to initially have the tank pumped 3-5 years after it is installed new. This first service will provide valuable insight into the condition of the septic tank and the accumulation of solids. The pumper can then recommend a schedule based on the thickness of the solids, together with other factors such as the time elapsed since the tank was new or last serviced and the number of people living in the residence. Remember, no one, and I repeat, NO ONE, can predict the future and the changes that life brings. If a pumper provides a recommendation for how often I should pump my septic, he is only basing his recommendation on what he sees today. Any changes in habits or lifestyle can, and will, affect the septic system. Furthermore, septic systems will not last indefinitely, so following the recommendation of a septic professional can never guarantee how long the system will last, or that it will remain trouble-free. However, there is overwhelming evidence that pumping your septic tank on a regular schedule will greatly increase the life expectancy of your system.

Besides removing solids, is there any other reason to pump my septic tank?

Yes, pumping your septic tank provides an opportunity to inspect the other components of the tank that can’t be seen otherwise. Inlet and outlet baffles, crucial components that protect the drainfield, can sometimes fail. Lids occasionally decay from gases produced within the system. A decayed lid can crumble and fall into the tank, which could be tragic if a child or pet happened to be walking across the area at the time. Pumping a septic tank allows it to be inspected for performance and safety, and, if necessary, small repairs to be made that could prevent a catastrophe later on.

I like to use the analogy of changing the oil in my car. If I change my oil on a regular schedule, my engine will last a long, long time, assuming I don’t abuse it in other ways. Similarly, if I pump my septic tank regularly, my drainfield will last for many years, as long as I don’t form habits that overload the system or harm it biologically. On the other side of the coin, if I wait until my car quits to change the oil, it’s probably too late to save it. Likewise, if I neglect septic maintenance until I have sewage backing up in my house, I have almost undoubtedly harmed my drainfield and shortened the life of the system. And, just like the auto mechanic who mentions that my brakes are getting worn while he is servicing my car, pumping my septic tank gives the pumper a chance to do a quick once-over inspection, hopefully fending off any costly failures down the road.

If you are needing to have your septic tank pumped, call Western Septic & Excavation at (208) 539-4207 today, or contact us via email to schedule an appointment. We look forward to hearing from you and, as always, will do all we can to ensure that your septic system lasts as long as possible.