How to Build a Septic Tank with Concrete Blocks?

The tank that stores wastewater of a house or building is called a Septic Tank. A septic tank, also known as a sewage collection system, is installed in homes to treat sewage on a small scale, which is common in areas with no connection to main sewerage pipes or where there is no proper drainage system. This tank is usually installed 1.5m-1.8m below the ground level. Wastewater-carrying sewer pipes coming from the house are connected to the septic tank. Most septic tanks can hold between 1,000 and 1,500 gallons of sewage. One end of a septic tank is connected to a wastewater inflow pipe, while the other end is connected to a septic drain field. Wastewater flows into the tank at one end and leaves the tank at the other. All the wastewater from the bath, toilet, and kitchen flows into the tank. Wastewater is pumped into this tank, where the heavier solids settle to the bottom. Heavy particles in wastewater are broken down into sludge and gases by anaerobic bacteria. Generally, if the density of solids is greater than the water, the solids settle at the bottom of the tank while the lower density solids float. The settled solids are called ‘sludge’, and the floating solids are called ‘scum’. Sludge microorganisms help speed up the decomposition of this solid waste. Grease and oil particles, among the least dense waste, float to the surface of the wastewater, where they accumulate as a scum layer. The septic tank is drained out after a specific period by sucking the waste throughout the outlet. There are a variety of materials that can be used to construct septic tanks, including concrete, concrete blocks, high-density plastic, fiberglass, and fiber-reinforced plastic. Metal tanks were once permitted but are now banned due to corrosion concerns.

Why Choose Concrete Blocks for Building Septic Tanks?

There are a variety of materials to think about and septic tank options to choose from if you’re in the market for a new septic system or just want to replace an old septic tank. There is a lot riding on the success of a new septic tank installation. Keep in mind that your new tank will serve an important plumbing purpose in your home for many years to come. When building your new septic tank, the material you choose will be among the most crucial considerations. Concrete block septic tanks are currently the industry standard. Concrete block septic tanks are widely used because of their weight, strength, and longevity. Septic tanks made from concrete blocks are less likely to leak or float if they are constructed properly. Maintaining a septic tank made of concrete blocks properly can extend its life span by decades or even centuries.

Many homeowners, lured by plastic tanks’ lower up-front cost compared to concrete blocks, fail to do a thorough cost comparison before making their decision. Spending less now may seem appealing, but a low-quality plastic tank may lead to greater maintenance costs down the road. Furthermore, fiberglass septic tanks are not easily available since they are not approved by many regulatory agencies. As opposed to the alternatives, septic tanks made from concrete blocks offer greater ease of use and other benefits. Comparatively, plastic and fiberglass need additional processing to make them watertight, but a concrete block has this property built right into it. Because of the concrete block’s inherent water tightness, leaks are less likely to occur over the tank’s lifespan. After a certain period, every septic tank needs to be pumped out. But there can be a sudden need to pump the tank if it fills up too quickly. There is less of a chance that homeowners will need their septic tanks pumped out unexpectedly when the tanks are made of concrete blocks. Septic tanks made of concrete blocks are relatively immune to damage from factors including shifting soil composition, tree roots, and weather. Septic tanks made of concrete blocks are better able to retain heat, which in turn encourages the growth of bacteria that break down the influent. Effluent from the tank and into your field will be cleaner as a result, which will be good for the health of the entire system. Concrete block septic tanks are more long-lasting and require less maintenance than their plastic counterparts. Concrete block septic tanks are the best option since they are the most cost-effective to install and maintain.

Steps of Building a Septic Tank with Concrete Blocks

1. Determine Size and Location

Think about how deep you want your septic tank to be. The height of the sewage pipe from the house to the septic tank entry is governed by municipal construction rules. In addition, the pipe used to transport wastewater from the septic tank to the lateral dump fields must be installed at the correct height. A survey team can analyze the site’s suitability based on the position of your property. A septic tank’s standard length and breadth ratio is needed for its size determination. A septic tank’s length to breadth ratio is typically 4:1 or 2:1. In most cases, the tank must be able to handle at least three thousand liters of wastewater. The daily wastewater volume will determine the optimal size of a septic tank. This amount is variable, as it is affected by factors such as the number of people living in the home and whether or not it is connected to both blackwater and greywater systems. Once installed, it might be challenging to make changes to a septic tank that was built properly. That’s why it’s important to take into account not just the number of people now living in a home, but the maximum number of people who may live there in the future based on its size and number of rooms.

2. Preparing the Pit

Dig out the pit where you will set up the septic tank. The soil from the pit is dug out, and the trenches for the pipes leading to and from the septic tank are dug using a backhoe. In order to provide the required fall (at least 1:80) from the toilet to the inlet to the septic tank, the depth of the pit will be determined by the depth of the septic tank. The pit’s width and length should be at least 2 meters longer than the septic tank’s. The pit must have a perfectly flat base. If the soil type is sand, a perimeter footing must be poured before construction can begin. Create a gravel bed at least 6 inches deep over the pit’s base. As a result, the ground beneath the septic tank will be more stable and less likely to shift or break.

3. Form the Floor Lining

The next step is to set up the floor of the septic tank. The floor of the septic tank must be made of reinforced concrete that is 100 mm deep and reinforced in accordance with local building codes. The reinforcing steel grid should be set at a depth of 30 mm below the finished floor. On top of this bed, pour the concrete to a depth of around 4 inches. Don’t move on to the following step until you’ve given this layer a day to dry out.

4. Build the Wall

Septic tank walls are typically made of concrete blocks reinforced with steel bars. Standard measurements for concrete blocks are 400 millimeters in length and 200 millimeters in height. After the flooring has been laid, a series of concrete blocks should be laid on top, with the hollow cores running horizontally along the edge of the dug pit to create the wall. There should be a gap of about 6 inches between their outside edges and the pit’s wall. Gravel is used to bridging this space of around six inches between the exterior of the blocks and the surrounding earth. It is recommended to stagger the second layer such that each block lays across the two below it, and then to alternate the placement in subsequent layers. Keep going until you’re within six inches of the ground, then stop. One common mistake is using mortar in the joints between the concrete blocks. The blocks should be placed without the use of mortar. The vertical steel rebar that was laid down in the floor pour should be used to reinforce the tank’s walls. By inserting the bars into the wet concrete, a solid structural connection is made between the walls and the floor. To ensure that the septic tank is completely watertight, all exterior blocks must be filled with concrete. A concrete additive and an expansion agent can help with block filling and increase water tightness, respectively.

5. Form the Inlet and Outlet Drain

Mark out a straight line from the house’s drainpipe’s exit point in the foundation to the pit’s inlet. Create a trench along that line, at least a foot wide and deep. The trench should slope away from the house and into the pit by at least 1 inch for every 50 feet as it is dug. Next, place lengths of 4-inch pipe (usually plastic pipe) in the trench and join them together.  One end must be inserted through the opening in the house’s septic pipeline, while the other must be inserted through the pit’s lining. About 6 inches of the pipe should extend down into the septic tank. The block can be drilled to accommodate the pipe end, or a block can be removed entirely.

6. Build the Roof

A septic tank lid can be made by the homeowner if so desired. However, constructing the cover yourself requires metalworking knowledge and experience. Instead, you should seek professional service. This process will be quicker and less labor-intensive. Get a concrete block manufacturing company to ship you a concrete roof that will fit over the septic tank’s lining’s outer diameter, and then have them set it up for you. The septic tank’s lid must be sized appropriately, and a manhole must be cut into the form before it is poured. Steel reinforcements are required for the roof, and huge steel hooks must be set into the concrete at each corner. Using a crane, gently position the roof on the tank by hooking onto the four steel hooks and lifting it off the sand bed. Once you’ve placed the cover, fill the rest of the hole and the drain trench with dirt and compact it firmly. At least six inches of topsoil should be placed over the tank cover and the trench. Septic tanks require access lids so that sludge can be periodically pumped out of the filter and the tank itself. The lid needs to be airtight and watertight. The lids must be easily accessible for servicing.

Septic Tank Maintenance

Septic tanks require regular maintenance to prevent them from becoming a nuisance to the neighborhood. Both surface water and groundwater contamination pose serious risks to human health and the environment. When the natural filtration system is impaired, contamination occurs. This can occur when a homeowner fails to do routine maintenance or when more water is used than the system can handle. Bacteria in the tank can become overworked if there is an excess of water or debris added to it. Waste is not decomposed effectively if this occurs. Please don’t put anything greasy (like fat, oil, or grease) down your drain since it will clog your septic tank. The walls of your septic tank might become coated and clogged with any of these substances. This keeps water from seeping into the ground and keeps the tank from working properly.

Professional draining and cleaning of a septic system are often required every two years. Clearing out the drains on a regular basis reduces the likelihood of a clog. When the sludge accumulates to a depth of three inches beyond the pipe’s suction point, it must be emptied. There is a possibility of odor coming from the pit because of the presence of waste gases. An effluent addition to the septic tank is done periodically to control odors. Reduce your reliance on chemical solutions wherever possible. Septic systems have a delicate biological equilibrium that can easily be disrupted. Any type of chemical, including those used for cleaning or oil changes, can quickly throw the system out of sync, and it can take a lot of work to get things back to normal. Maintain thorough documentation of all servicing works.

Do not attempt to repair a septic system on your own; doing so can be extremely hazardous, if not lethal. The replacement of the leach field necessitates the use of heavy machinery due to the need for excavation and, most likely, pipe replacements. Additionally, your septic tank has a wide range of gases in it. Some of these gases can be lethal with little warning if inhaled. To ensure the safety of everyone involved, a septic tank should only be serviced by trained personnel.

Summary

The installation of any septic tank should only be undertaken by a qualified professional. A septic tank system is a long-term investment, therefore it’s important to take a close look at the installation site before making any moves.  Choose only concrete block septic tanks to guarantee that your system will perform as intended and meet all applicable regulations. Most drainage issues with septic tanks can be traced back to faulty construction. Therefore, employ a qualified professional to carry out the installation.

F.A.Q.

How does a septic tank work?

Ans. Household wastewater flows into the septic tank through an entrance pipe, where solids settle and scum floats to the top. The solid waste undergoes an anaerobic digestion process that causes them to settle and shrink in volume during its retention.

Are there any drawbacks to using a septic tank?

Ans. It is possible for the inlet drains of a septic tank to become clogged due to the excessive disposal of cooking oils and fats in the tank’s upper portion. In addition, if there is too much water in the septic tank because of a plumbing leak, the system could get overloaded.

When should a septic tank be pumped out?

Ans. Septic tanks should be emptied at least once every two years, but with proper maintenance, this interval can sometimes be extended to every three to five years.

Which material is best for septic tanks?

Ans. As a result of its durability, sturdiness, and low maintenance requirements, septic tanks made of concrete blocks are a popular choice. Compared to other materials, a septic tank constructed from concrete blocks can last for decades.

How to calculate the size of a septic tank?

Ans. Septic tank sizing guidelines might greatly differ depending on waste volume, home area, and perhaps a few other variables. The minimum size of a septic tank required in a given area varies over time and is determined by governmental regulations.