What Size Septic Tank For 4 Bedroom House?

Knowing the right size of a septic tank for your 4-bedroom house is crucial for maintaining a healthy and hygienic environment. A septic tank that is too small can cause frequent backups and overflows, while an oversized one can lead to unnecessary expenses.

This guide will explore various tank types, unravel the determination process, highlight influencing factors, and offer maintenance tips to safeguard your home’s sanitary system.

What Size Septic Tank For 4 Bedroom House

For 4 bedrooms, you will need a 1250 – 2500 -gallon septic tank. This is the minimum size tank for your 4 bedrooms. You may need a larger tank if you have a larger home or more than four bedrooms. Remember that the septic tank size you need will also depend on the water you use.

4 Bedroom house Septic Tank Size Chart:

Number of Bedrooms	Minimum Septic Tank Size	Minimum Liquid Surface Area	Drain field Size
2 or less	1000 – 1500 Gallons	27 Sq. Ft.	800 – 2500 Sq. Ft.
3	1000 – 2000 Gallons	27 Sq. Ft.	1000 – 2880 Sq. Ft.
4	1250 – 2500 Gallons	34 Sq. Ft	1200 – 3200 Sq. Ft.
5	1500 – 3000 Gallons	40 Sq. Ft.	1600 – 3400 Sq. Ft.
6	1750 – 3500 Gallons	47 Sq. Ft.	2000 – 3800 Sq. Ft.

As you can see, the septic tank size you need will also depend on the number of bedrooms in your house.

In addition to the number of bedrooms in your house, the septic tank size you need will also depend on the water you use. 

You will need a larger septic tank if you have a family of four that uses lots of water.

However, if you have a family of four that uses less water, you may get away with a smaller septic tank.

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What Does The Size Of The Septic Tank Depend On?

The size of the septic tank needed will depend on various factors. In the below part, we will give some details about these factors:

The Specific Septic System Type

You can find the specific septic system type right for your home by researching. The tank size may vary depending on the type of septic tank system you want to use. 

There are seven different types in total. In-depth explanations of system types and their size requirements are not the focus of this article.

When we say conventional, gravity-fed anaerobic septic systems here, we mean standard ones.

The most common type of septic system is the anaerobic one, which most people think of when they picture a septic tank.

Below are the eight most common types of septic systems.

1. Conventional, Gravity-Fed, Anaerobic System
2. Above Ground Septic System
3. Pressure System
4. Aerobic System
5. Mound System
6. Recirculating Sand or Gravel Filter System
7. Bottomless Sand Filter System
8. Local Government Regulations

Local government regulations may also dictate the size of your septic tank.

The last thing you want is to install a septic tank that does not meet the requirements set forth by your municipality.

Contact your state or county health department to find out what the local codes and regulations are. They will be able to tell you what is required in your area.

For example, the WST is a document that serves as an informational overview of codes, rules, and regulations often imposed by administrative authorities, as well as common jargon and definitions.  

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Suitability Of The Ground Geology

The underlying ground geology will also play a role in the size of the septic tank you need.

The decision will contribute to the soil type, water table level, and percolation rate.

If you have sandy soil, you will have a higher percolation rate. Your septic tank will not need to be as significant because the soil will allow more water to seep through.

On the other hand, if you have clay soil, you will have a lower percolation rate.

Your septic tank will need to be more significant because the soil will not allow as much water to seep through.

The water table level is another factor to consider.

If the water table is high, you will need a larger septic tank because the water will not be able to seep into the ground as easily.

The Expected Volume Of Wastewater

The final factor to consider is the expected volume of wastewater.

This includes all the water that will go down the drains in your home and any water that will be discharged from appliances such as washing machines and dishwashers.

You will need a larger septic tank if you have a family of four that uses a lot of water.

However, if you have a family of four that uses less water, you may get away with a smaller septic tank.

So, these were some of the critical factors on which the size of a septic tank depends. When you get your septic tank installed, keep these things in mind.

This way, you can be sure that you are getting the right size septic tank for your needs.

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How To Calculate The Size Of The Septic Tank You Need

Now that you know the key factors that will dictate the size of the septic tank you need, it’s time to learn how to calculate the actual size.

First, you must use some equations to calculate the size of a septic tank. C = A + P (rq +ns). C is the septic tank capacity in gallons. 

A=constant. P is the number of users. r = minimum retention time, q = average sewage flow in liters per person per day, n = number of years sludge will be stored, and S = rate of sludge accumulation in liters per person per year.

We can simplify this further: A = 2000 liters in British code, rq + ns = 180 liters, so the rounding method is rn/1000.

So, C = 2000 litres + 180P.

Assume we must determine the capacity of a septic tank for four users. What should we do?

C = 2000 litres + 180 × 4 = 2720 litres,

The minimum size of a septic tank for four people is 2.2m × 1.0m × 1.30m (7.2ft × 3.3ft × 4.25ft). 

Its length, breadth, and depth might be considerably bigger or smaller based on the user’s needs or local conditions.

Overall, the tank should be 6ft tall, including the depth of the liquid waste. 

This will ensure that there are 1 to 1.5ft of free space above water level inside the tank. The tank capacity should be 2800 liters.

On the other hand, if you have a family of four that uses less water, you may get away with a smaller septic tank.

So you can use the following equation: C = 2000 liters + (180/4) P. 

How To Plan A Septic Field

After the septic tank, the next step in the process is the septic field. The septic field is a series of trenches that are filled with gravel. 

The trenches allow the wastewater to seep into the ground and be filtered by the soil. There are a few things to keep in mind when you are designing your septic field. 

First, you need to make sure that the trenches are wide enough. The width of the trench will determine the amount of water that can seep through.

Second, you need to make sure that the trenches are deep enough. The depth of the trench will determine how long it takes for the water to seep into the ground.

Third, you must ensure that the trenches are spaced far apart. The trench spacing will determine how long it takes for the water to seep through the gravel and into the soil.

Finally, it would be best to ensure that the gravel is the right size.

The gravel should be small enough to allow the water to seep through but large enough to filter out the solid waste.

Now that you know the basics of septic field design, you can start planning your system.

Remember to keep the above factors in mind, and you will be well on designing a successful septic field.

How Deep Should A Septic Tank Be?

The depth of a septic tank is an essential consideration in the system’s design.

The depth of the tank will determine how long it takes for the water to seep into the ground.

There are a few things to remember when determining the depth of your septic tank.

First, you must ensure the tank is deep enough to allow the water to seep through the gravel and into the soil. 

Second, you must ensure that the tank is deep enough to allow the solid waste to settle out of the water.

Finally, ensuring that the tank was deep enough to allow the sludge to settle out of the water would be best.

The depth of the tank will determine how often it needs to be emptied.

As a general rule, the septic tank should be at least 5-6 feet deep. This will ensure the water has enough time to seep through the gravel and into the soil.

It will also ensure that the solid waste has enough time to settle out of the water.

What Are Alternative Septic Systems?

Alternative septic systems are designed to treat wastewater without using a septic tank. You can find a few different types of alternative septic systems on the market. 

Below we will give some alternative septic system reviews:

Mound Systems

Mound systems are designed to treat wastewater without using a septic tank.

Mound systems use a series of pipes and pumps to transport the wastewater to a higher level. 

The water is then discharged onto a mound of soil. The mound of soil acts as a natural filter, and the water is eventually absorbed into the ground.

Mound systems are a good option for areas with high water tables. Mound systems are also a good option for areas with poor drainage.

Pressurized Dosing Systems

The pressurized dosing system lives up to its name by using pressure to distribute effluent into the leach field in more even, measured doses! 

Leach fields can be challenging to keep clean.

With the measured approach for distributing effluent, this technique may be ideal for rehabilitating a leach field after a septic system failure. 

This method only focuses on soil effluent dispersal so that it can be combined with any below-mentioned water treatment system.

Plastic Chamber Leach Field

This system is designed to take advantage of the soil’s natural ability to treat effluent.

The leach field is made up of a series of interconnected chambers that are buried underground. 

These chambers are perforated, allowing effluent to seep into the surrounding soil. The soil then treats the effluent before it returns to groundwater.

Plastic chamber leach fields are a good option for areas with high water tables. Plastic chamber leach fields are also a good option for areas with poor drainage.

Aerobic Treatment System

The aerobic treatment system infuses oxygen into the tank via an air pump, intakes outside air, and transfers it into the septic tank. 

This process creates aerobic conditions, which allow bacteria to break down waste more efficiently.

The effluent is then discharged into a leach field, where the soil treats it.

So these are some of the different types of alternative septic systems you can use. Be sure to do your research before deciding on which system is suitable for you.

FAQs

Final Thoughts

It is essential to research before deciding which alternative septic system is suitable for you.

Be sure to consider the size of your tank, the water you use, and the type of soil you have. 

With a bit of planning, you can find the perfect septic system for your home. After reading this article, you know what size a septic tank is for a 4 bedroom house.