Everything You Should Know About How Your Home's Septic Tank Works

Septic tanks are a lot easier to understand than you might think. If you have only ever relied on city water and sewer systems, transitioning to a home with a septic tank might seem a bit overwhelming at first. However, mastering the system's purpose, design, and upkeep is actually relatively simple for most people. You might have heard horror stories about septic systems overflowing and ruining the yard or just how difficult they are to maintain — yet once you know the basics, you aren't likely to struggle at all. In fact, you might find that you actually come to prefer a septic tank over other waste management options because of their cost savings, as you won't need to foot monthly sewage removal bills.

We'll explain each component of your system, how to take care of it, and how everything works together to keep your wastewater flowing freely. Whether you're wondering what you need to know about septic systems before buying a house, or are already living on a property that has one, this guide will walk you through how they function and some important dos and don'ts to help you maintain your system. Buckle up to find out when to get your tank pumped, what to avoid putting in it, and more. 

A septic tank is the biggest part of a system that removes wastewater from properties that are not connected to the local city sewer system. Sometimes this is because you live more remotely, or because your area just doesn't have the infrastructure. Whatever the reason, the tank takes the place of the local sewage treatment plant and your home's waste technically remains on-site.

These tanks come in many different shapes and sizes, as well as in different materials. What remains consistent, however, is that they are typically buried in the backyard. They are far enough underground that you shouldn't be able to see or smell them if they are working correctly. They do require some maintenance and upkeep, but it's not a daily task. The system consists of the septic tank itself, pipes entering and leaving the tank, the distribution box (D-box), and a drain field — all of which work together to treat the wastewater and keep your home up and running!

If you've never lived in a home with a septic tank, it's important to understand how they work so you don't end up with any sewage backups. If you're on city water, when you flush the toilet or rinse something down the sink, it gets whisked away to a treatment plant. However, with a septic system, it flows through a pipe and settles into the tank chamber. Inside the tank, the heavier materials should sink to the bottom, which creates a thick sludge. Lighter materials like oil or grease tend to float up towards the top and form a layer of scum. There are lots of bacteria in the tank that consume any organic matter, helping to slow the build-up of sludge so the tank doesn't get too full too fast.

Then, the leftover liquids exit the tank through a secondary pipe. This liquid is called effluent. This secondary pipe has another filter on its entrance to keep most of the solid waste from coming through. The liquid flows down into the drain field, which is made up of pipes with holes buried in gravel or sandy trenches. In the drain field, the liquid spreads out into the soil.

Septic tanks are typically made from three main types of material: concrete, plastic, and fiberglass. In the past, tanks were also made of metal. However, they rusted too easily and could be prone to leaking. If you still have a metal tank, you'll likely need to replace it due to this problem.

There are pros and cons to each type of septic tank material. Concrete tanks are durable and can last decades, as they are resistant to buoyancy in high water table areas, but their heavy weight increases installation costs and makes them prone to cracking over time. Plastic tanks are relatively lightweight and can be easy to install. They are resistant to rust and corrosion, but their low weight makes them vulnerable to shifting in areas with high groundwater, if not properly secured. Fiberglass tanks are very similar, although they are more expensive and require careful handling during installation. The best choice for your property largely depends on your budget, the landscape, and the type of soil.

Having anaerobic bacteria present in your septic tank is essential for it to function properly, as the bacteria help break down the waste. Anaerobic means without oxygen, and these types of bacteria thrive in the oxygen-free environment of the septic tank. They are responsible for digesting all the solid waste that settles on the bottom of the tank. This consumption helps lengthen the amount of time it takes for the tank to fill up, so you don't have to pump it as frequently.

Additionally, the bacteria work together with the filter on the exit pipe to help keep large chunks of waste from making their way into the drainage field and clogging things up, or overflowing into the yard. Finally, septic tank microbes can also consume or outcompete pathogens in the effluent. While they might not be able to eradicate every unwanted bacterium, under the right conditions, these little organisms are a big part of what keeps septic tanks functioning safely. 

D-box is short for distribution box. It's the part of the septic system that makes sure the effluent flows correctly from the septic tank down into the drain field. As the name might suggest, it's a small box that acts as a bit of a checkpoint for the wastewater as it goes through the system.

Even distribution of the effluent is very important because it helps stop any overloading of specific areas of the drain field. If not done correctly, this overload could lead to sewage backups, uneven drainage, or a total system failure — which is likely to be expensive to fix and smells awful. If you were to take a look inside the D-box, you would notice multiple outlets connected to the drain field pipes. If the D-box is damaged, it can cause some of these pipes to receive too much or too little wastewater, leading to uneven load on the system and the bigger problems mentioned.

You might also hear the drain field called the drainage field, leach field, or absorption field, but they are all the same thing. It is the last stop in the septic wastewater management process. Different municipalities will have different rules about how close a drainage field can be to your home, as well as its total size and depth. However, the field is most usually a network of perforated pipes that are laid in gravel-filled trenches beneath the soil. The holes in these pipes help with the distribution of the effluent into the surrounding soil.

The soil then further breaks down any leftover harmful bacteria or viruses left in the wastewater. However, things like using too much water, compacting the soil, or flushing items that don't break down can overload or harm the drain field, causing it to fail.

It's important to know the differences between gravity and pump septic systems, as each type has its own benefits and drawbacks that can fit different needs and different types of properties. As its name might suggest, a gravity system uses natural forces to transport wastewater away from your home. It's a pretty simple, low-cost system that doesn't have any internal moving parts. It needs less overall maintenance because of this, too. It's best suited to land that has natural slopes — if your property is too flat or uneven, things might clog up.

On the other hand, a pump-assisted system is one that uses an electric pump to move the wastewater. This makes it a good choice for properties where gravity can't really do the job, like flat areas or someplace where the drainage field needs to be higher than the tank. While these systems give you plenty of location and design flexibility, they usually do cost more to install because of all the moving parts. The pumps also need more maintenance than a gravity-based system, and will require more frequent (usually yearly) inspections from your septic tank pumping company.

Eventually, the bacteria in the tank won't be able to manage the amount of sludge on the bottom. While the wastewater will continue to flow through to the drain field, it will have less and less room to do so over time as the scum builds. To prevent your tank from overflowing or cracking due to becoming overfilled, you need to pump the scum out of the tank.

If you're wondering how often you should pump your septic tank, the answer can be a little convoluted. The exact time frame will depend very much on the number of household members and how much time they spend at home. Average-sized households with correspondingly sized systems generally need to get their tanks pumped out every 3-5 years. Larger households or those where the majority of occupants spend at lot of time at home might need to pump their tanks annually or every two years. Also, take note that tanks should be inspected and emptied long before they're full of sludge. The EPA recommends pumping when scum and sludge makes up 25% of the liquid. This reduces the chance of sewage backups and solids entering the drain field. It also ensures that the bacteria can function well, as overly full tanks can inhibit their activity. Average-sized systems require inspections every three years at a minimum. If it's been a couple of years, or you're not sure when last your tank was emptied, call in a professional pumper to do an inspection. One of the most important things to know before pumping a septic tank is that this isn't a DIY job — you need to hire a company that can suck out the waste and haul it away for you.

When you have a septic system, you need to be a little bit more careful about how you create wastewater in your home. Because, if things go downhill, it'll be you footing the expensive clean-up and maintenance bill. As you now know, septic systems rely on a balance of bacteria to break down waste, and flushing too many of the wrong things down the toilet can really mess things up. Human waste and toilet paper are the only things you should be sending to your tank. Common items like paper towels, feminine hygiene products, baby wipes (even those labeled "flushable"), diapers, and cotton swabs do not break down properly and can block pipes or accumulate in the tank. It's important to use septic-safe cleaning products that won't damage your system, and there are even certain types of toilet paper you might want to avoid using in a septic tank.

Another thing to be mindful of is how much water you use. Heightened water use from appliances, plumbing leaks, additional occupants (such as visitors or the arrival of a baby), or hot tubs can overwhelm the tank's drain field. Aim for consistent water usage, so that the system doesn't suddenly become filled or clogged. If high water usage is taxing your septic tank, implement water-saving measures such as only doing full dishwasher loads, tailoring the water level to suit load size when doing laundry, and shutting off faucets when shaving at the sink or brushing teeth. You might also want to look into installing a low-flow toilet and showerheads, faucet aerators, and water-saving appliances. Lowering the water pressure in your home by installing a pressure valve can also help reduce the amount of water entering your septic tank. 

When you know what to look for, it's pretty easy to tell if your septic tank is working as it should. The most important thing to remember with these systems is that mostly, no news is good news. You want the ground above your tank to be relatively dry — meaning there is no puddling or water pooling in the yard. The grass should be overall green and lush, as there is so much natural fertilization happening beneath it. You should not be able to smell your septic system.

Signs of trouble include things like slow-draining sinks or toilets, unpleasant sewage odors coming from toilets, drains, or the yard, or wastewater pooling near the drain field. If you notice any of these, schedule an inspection of your septic tank right away before things start backing up or leaking. If it's just the toilet that's giving off an odor, here is a guide on why your toilet smells like sewage (and what to do about it), which can help you eliminate other issues, like a dry P-trap.

Yes, severe storms and big temperature changes can absolutely affect your septic system. For example, lots of rainfall can saturate the ground around your drain field (especially if it's heavy clay), and slow down the rate at which your septic tank drains. If a storm brings severe flooding, the excess water could compromise and overwhelm both the drain field and the tank. Most septic tank systems rely solely on gravity, but if you have an ATU (where the waste is aerated via a pump) or a system where waste has to be pumped uphill — flooding and power outages can affect their operation. If the power is out for more than a few days, you may start to notice very foul smells wafting up from your pipes. In these cases, be sure any power the tank needs is switched off so it doesn't surge when electricity is restored. Limit water usage to a minimum in the meantime so the drains don't overflow, and get a professional out to check things over as soon as possible. 

Snow and freezing temperatures can also impact the efficiency of your septic tank, as parts of it can begin to freeze. If you are using your tank every day, the heat of the sewage is likely to keep things moving — but if you go away, ask your house sitter to run some water or flush the toilet when they visit to simulate this. If your system is prone to freezing, here are some steps you can take. Have any water leaks fixed before the start of winter, as a small but continuous stream of water can create ice dams where your wastewater pipe exits the home on its way to the septic tank. You can also insulate this sewer line exit point, the tank itself, and the area above the D-box with a thick layer of hay, leaves, etc. Snow fences can also help trap snow in these places, which can act as an effective insulator, especially if it's not compacted. 

When planning your yard it's important to consider how landscaping can affect your septic system. Whether you need to change some of your landscaping to prevent future issues, or head them off at the pass by not creating them at all — these are the things to look out for. The first is tree roots. Roots are powerful, living things that can break through concrete sidewalks. If they get close to the tank, they can potentially cause damage to it. Tree and shrub roots can also grow into the drain pipes, potentially blocking and cracking them. Thanks to this, you should avoid planting trees and shrubs around septic tank covers (and corresponding drainage fields) that have extensive or aggressive root systems, like willows and woody shrubs.

You should also install things like swimming pools, decks, sheds, play sets, and driveways away from the drain field to protect it from damage. Spending time on the lawn areas above the drain field shouldn't be dangerous to you (provided the system is functional), but erecting these features in the direct vicinity can compact the ground and reduce drainage, thereby compromising the system. To avoid waterlogging in the area, direct runoff away from the drain field, and sprinklers should not be used here. We just mentioned that drain field areas aren't unsafe to have in your yard, but there is one thing to avoid due to health implications: Never create a vegetable garden near a septic tank or drain field. There may be a risk of pathogens and pollutants, and, as with ornamentals, the roots of some edible plants could interfere with the system. Any compost or fertilizer used will add to the nutrient load (which will already be elevated) that the soil has to process.

Yes, there is usually a risk when adding chemicals to your septic tank. Common household products like bleach and antimicrobial cleaners can be detrimental to the bacteria in your septic tank, so try to limit your use of these. Most households have to utilize a certain amount of antibacterial products, especially in the bathroom, and conservative use might not be an issue, but do not flush these down the drain or toilet on a daily basis. Besides cleaners, be careful of septic system additives that claim to fix issues with your tank or plumbing. While they may seem like a cost-effective, smart idea, these products can actually harm both the system and the environment. Inorganic additives, like strong acids or alkalis, can damage septic function, corrode tanks, and harm soil. Organic solvents, which are often used to break down grease, can also kill beneficial microbes and risk groundwater contamination. 

Finally, any sort of biological additive, while marketed to enhance bacteria, is actually unnecessary, because septic systems naturally maintain their own microbial balance. Instead of flushing chemicals or additives into your septic tank to keep it healthy, focus on proper maintenance like regular pumping, not overloading the system with wastewater, and keeping any pesky tree roots away from it.