Septic tanks for a private home - put them on shelves

A septic tank is a local wastewater treatment system, part of an overall septic system, which consists of a tank, pipes and a drainage field.

Septic tanks are usually used in situations where connecting a house to a city centralized sewerage system is impractical or impossible. If you live in an area remote from municipal services, then most likely you have such a system.

The material was created with the support of the Top Septic website:
septic tank for a summer residence

The wastewater in the tank is treated by physical and biological means through the following processes:

Sedimentation is the process by which suspended particles in wastewater settle to the bottom of the tank. This accumulation of solids at the bottom of the tank is called sediment.

Flotation - When the sludge settles, the oil and grease float on the wastewater in the tank, forming what is called sludge. When organic waste is decomposed by bacteria, gases such as methane can be released, which also settle in the sediment layer.

Anaerobic digestion is a process in which bacteria and enzymes break down organic matter in the absence of oxygen.

A properly functioning septic tank should be able to eliminate 25-35% of biochemical oxygen demand and at least 60% of solid waste. As the solids settle to form layers of sludge and waste, the clarified liquid is directed into the drainage field.

How do septic tanks work?

Wastewater from toilets, sinks and laundry rooms flows out of the house through pipes into the septic tank. These tanks are usually designed to hold wastewater long enough for solids to settle to the bottom (forming sludge) and oils and greases to float to the top (sludge). The layer of sediment helps keep the tank sealed, which helps anaerobic bacteria better digest organic waste. It is recommended to pump out the tank after a couple of years, otherwise some of the solids will end up in the drain field, which can lead to clogging. The frequency of pumping will depend on how much inorganic matter is in the tank. Avoid discharging inorganic waste into drains. You can also optimize the process of biodegradation of organic waste by adding biological additives.

Partially purified water from the tank flows through the outlet into the drainage field. This wastewater then seeps into the soil through small holes in the pipes. Microorganisms in the soil remove harmful particles remaining in the wastewater. Treated water enters groundwater and returns to the water cycle.

Types of septic tanks

Septic tanks can be classified based on the material used or the size of the tank. Listed below are the common types of septic tanks.

Concrete septic tanks

Concrete septic tanks are the most popular because they are cheap and do not deteriorate quickly. Concrete septic tanks are usually prefabricated, making them easy to install on site. However, it is also possible to have a custom septic tank built to suit your unique needs.

Although septic tanks can last for decades, they are also susceptible to cracking, especially if installed incorrectly. Research also shows that concrete septic tanks can suffer from corrosion. Some bacteria in a septic tank produce hydrogen sulfide, which usually remains dormant in the tank. Subsequently, a strain of thiobacillus bacteria converts the hydrogen sulfide into sulfuric acid, which can eat away at the concrete. However, concrete walls are usually large enough to withstand minor corrosion, so new tanks will remain in good working order for decades.

Polyethylene septic tanks

Such septic tanks are lighter than concrete ones, which makes them very convenient for transportation and installation. These containers can withstand corrosive gases without being destroyed. They are also not susceptible to cracking or rusting. However, polyethylene tanks also have their disadvantages. For starters, while their lightness makes them easier and cheaper to transport and install, their thin walls make them an easy target for structural damage. If handled carelessly, they can be easily damaged during installation.

Fiberglass septic tanks

Fiberglass tanks are also lightweight, making them very easy to transport and install. They are more durable than polyethylene, and even if they fail, they will leak rather than burst. Fiberglass tanks are usually custom-made, which combined with the complexity of the technology makes them quite expensive.

Steel septic tanks

Steel tanks are designed to last 20-25 years, but they will rust so may last less time. Compared to other types of tanks, steel tanks are the least durable. Therefore they are not very popular nowadays. If you have a steel septic tank, pay attention to the baffles because they rust faster than other components. Steel top caps can also rust and this can pose a serious health hazard as a person stepping on them can easily fall into the tank. Since the caps can be replaced without replacing the tank, it is worth doing this as soon as signs of rust appear.

What to consider when choosing a septic tank

Tank size – This is determined by the size of the house and how much water is used.

Material used - There is no one type that fits all. An engineer’s advice will be needed to determine which material is best to choose based on soil type, groundwater level, associated loads and other important factors. For example, if the groundwater is high, a concrete tank is likely a good choice because it is not as prone to floating as polyethylene and fiberglass.

Tank Type – In addition to the different materials available, the type of tank may also be determined by the number of compartments. The single-compartment tank does the job well, but is not very common since the two-compartment tank does a better job of removing total suspended solids.

Soil Type – The type of soil on the property will greatly influence the choice of septic tank. Before purchasing a septic tank, an engineer should conduct a soil analysis and make recommendations based on the results.

Gray water tanks

Gray water is considered to be any domestic water, with the exception of water from the toilet and kitchen (black water). This means that it is necessary to have two separate tanks: one for receiving gray water and the other for black water. On average, 50-80% of all domestic wastewater is gray water. In most cases, gray water ends up in a small drain field and black water ends up in a reservoir. The reservoir is pumped out periodically. Fresh gray water is not as harmful as black water. However, gray water decomposes faster than black water, and if it is not treated within 24 hours, gray water will turn into black water.

Reservoirs for “black” water

A black water tank, also called a septic tank, should not be confused with a septic tank. A septic tank is the first stage of wastewater treatment. However, black water tanks provide only temporary wastewater storage. Unlike septic tanks, which have outlets, a wastewater tank only has an inlet, fills quickly and requires regular pumping. Therefore, they can be equipped with an alarm and a sensor that alerts the owner when the tank needs to be pumped out.

Septic tank design

Although septic tanks can be made from plastic and fiberglass, the most commonly used material is concrete. Tank sizes vary, but the most common are tanks with a volume of 5 to 12 cubic meters.

The ideal size of a septic system for a home is determined by two main factors – climate conditions and the number of users. A large farm requires a larger septic tank to cope with bulk wastewater.

Those living in the north or other cold regions will also need to increase the tank size. This is because the colder the temperature, the slower anaerobic bacteria will break down organic solids. According to some experts, septic tanks in persistently cold areas should be twice as large as septic tanks serving the same number of people in warmer regions.

Before designing and installing a septic tank on a site, it is necessary to have a wastewater treatment specialist conduct a soil assessment. This check is important for various reasons. The inspection will help identify some weak spots in the soil so you can know how best to overcome them when designing and installing the system. This process is only necessary when installing a new system.

Choosing the right septic tank material is very important as it affects not only the cost but also the longevity of the tank. Tanks can be made from concrete, polyethylene, fiberglass, and even coated steel. Small septic tanks are usually prefabricated (they are shipped pre-assembled), but larger tanks can be built on site or assembled from prefabricated sections.

Plastic tanks are growing in popularity because they are lightweight and easy to transport. However, concrete tanks are still most ideal for situations where the groundwater level is high, as they are less susceptible to rising. Concrete tanks can also withstand greater depths than other types of tanks. The biggest advantage of polyethylene and fiberglass tanks over concrete ones is that they are not susceptible to the corrosive effects of sulfuric acid and hydrogen sulfide, which are often found in wastewater. However, concrete tanks can be reinforced to allow room for minor corrosion, and the concrete can withstand large associated loads.

How much do septic systems cost?

Depending on the material, design of the septic tank, installation location and complexity of installation, as well as the necessary work on laying sewer pipes and removing earth, etc., the cost of a septic tank can start from 40-50 thousand rubles in 2022 prices.

Can a septic tank be repaired?

Tiny cracks that do not cause a leak do not need to be repaired, but if the tank is leaking, repairing it is critical. However, some damage is too severe to repair and may require a complete overhaul of the system. The contractor typically uses concrete filler to repair cracks in the concrete tank. Before repairing tanks, they must first be pumped out and cleaned.

Climbing into tanks is extremely dangerous and should only be done by qualified contractors. In addition to the risk of physical injury, tanks also contain many harmful gases. Contractors have special equipment and safety gear that helps them complete repairs or replacements without any mishaps.

How many covers should a tank have?

Most septic tanks have two covers, which are usually located above the inlet and outlet. Covers vary in shape, material and size depending on the type of structure used. Septic tanks with only one lid are very rare.

What is a “fan boner” for?

A septic tank riser is a cylindrical pipe that is located above the septic tank. Its width is usually 5-7 cm and its main purpose is ventilation. Deep tanks should have wider risers. A large diameter riser, depending on the design, can be used to pump out the tank without having to open the lid.

Are filters necessary for a septic tank?

In an ideal scenario, only wastewater would flow into the septic system. In this case, bacteria decompose organic waste, and water flows through the outlet into the drainage field, so a filter is not needed. However, ordinary households knowingly or unknowingly flush all kinds of harmful waste down the drain. As solids accumulate in the sludge layer, some may eventually be forced into the drainfield. In this case, the filter will help reduce the likelihood of clogging of the drainage field, and the system will work optimally longer. The filter should be cleaned twice a year - before and after winter.

What should not go into the septic tank?

The optimal functioning of a septic tank depends on bacteria and enzymes. Enzymes break down waste into smaller molecules, which helps bacteria digest it. This leads to liquefaction of organic waste. Every septic system owner should avoid using any products that pose a threat to the bacteria and enzymes in the septic tank. The following are examples of foods that are harmful to septic tanks:

• Grease, oil and grease
• Dishwashing drains and washing powders
• Brighteners and fabric softeners
• Toilet cleaners
• Facial tissues
• Cigarette butts
• Dental floss
• Tampons, sanitary napkins and pads
• Baby wipes and diapers
• Latex condoms
• Expired pharmaceuticals
• Antibacterial soaps and disinfectants
• Corrosive and toxic products
• Antifreeze
• Drain cleaners

How full should a septic tank be?

During normal operation, the septic tank should be filled to the bottom of the outlet pipe. The outlet pipe must divert wastewater to the absorption zone, thereby maintaining the desired level. On average, the liquid should be approximately 40-50 cm from the top of the tank. If the level rises above the drain pipe, this means that the drain outlet is blocked and immediate action must be taken.

Here are some signs that your tank is overfilling:

A clogged drain almost always means that the drain field or pipes in the system are clogged. The lowest drains in the house, such as the bathroom and basement, are affected first.

Pooling of water – If puddles of water form around the septic system, it may be a sign that the tank is overfilled.

Unpleasant odors – a non-functioning drainage field often results in unpleasant odors. If you notice unpleasant odors coming from your septic system, take action immediately.

Slow Draining – A slow moving drain can mean a simple clog in the pipes, but overflowing septic tanks also lead to slow draining.

Greener grass above the septic tank – The grass above the septic tank should be the same as the rest of the lawn. If the grass above the septic system appears greener and healthier, this is a sign that the tank is too full and is now leaking.

Let’s sum it up

If you have a septic system installed on your property, be sure to take care of it. A well-maintained system will function optimally, while a neglected system will fail and pose a threat to the environment. Some simple maintenance procedures, such as using biological additives, not draining harmful products into the septic tank, and avoiding hydraulic overload, will help the system last a long time. Here are some important points to remember:

The main task of a septic tank is to retain as much organic waste as possible, while purifying the water through physical and biological processes. Sedimentation, flotation and anaerobic digestion are the main methods used.

The tank must be pumped out at least once every 2 years.

Materials commonly used to make septic tanks include concrete, polyethylene, fiberglass and steel.

The size of the septic tank will be determined by the number of bedrooms in the house. For example, for homes with one or two bedrooms, a tank with a capacity of 3-5 cubic meters may be sufficient, while for homes with 6 bedrooms, a tank with a capacity of 12-15 cubic meters will be required.