How Many Bedrooms Can a 1000 Gallon Septic Tank Support?

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How Many Bedrooms Can a 1000 Gallon Septic Tank Support?

So, how many bedrooms can a 1000 gallon septic tank support? The short answer is up to 3 bedrooms. However, the exact figure depends on other factors, such as the square footage of your house and the volume of wastewater you generate.

Continue reading to find out why does the size of septic tank matters in the first place, the different methods of calculating the right septic tank size for your home, and the estimate cost of installing a septic system.

farmhouse with 1000 gallon tank

Why Septic Tank Size Matters?

All the water that leaves your home from your shower, toilets, kitchen, and laundry ends up in your septic tank. In other words, your septic system is the first stop for all your wastewater, where it stays for as long as 24 hours, during which the solid waste is separated from the liquids.

This retention period is important to ensure solids get effectively separated from the liquids. It is the job of bacteria and enzyme living in the tank to separate the solid waste and break them down into liquids and gasses.

The size of the septic system is a primary factor that determines how efficiently the tank’s ecosystem can separate and decompose the solid waste. In case the tank is too small, the wastewater forcefully gets flushed out prematurely before the solid waste has a chance to settle down.

That’s because the tank system needs to create room for more incoming wastewater. The only way it can do that is by flushing out the wastewater that’s inside it —  regardless of whether it has been properly treated or not.

However, this doesn’t mean having an unnecessarily large tank is advantageous?

If the tank is too big for the volume of wastewater you generate, it would mess up the bacteria forming. As you may guess, that, in turn, will reduce the system’s efficiency considerably. See the Dimensions of 1000 Gallon Septic Tank and Different Septic 1000 Gallon Tank Types Here

In short, the size of the septic tank must be appropriate for your needs — neither too small nor too big.

What are the Different Methods of Calculating the Septic Tank Size for Your Home?

There are two main methods of calculations to determine the right septic tank size for your home — house size and water usage.

  • Calculations by the Number of Bedrooms

Some local authorities use the number of bedrooms or the square footage instead of the estimated wastewater flow to guide homeowners in picking a septic system size.

So, what are the recommended septic tank sizes based on the number of bedrooms in a house?

Here’s a table that you can use for reference.

No. of BedroomsHouse Square FootageTank Capacity
1 or 2Less than 1,500750 gallons
3Less than 2,5001,000 gallons
4Less than 3,5001,250 gallons
5Less than 4,5001,250 gallons
6Less than 5,5001,315 gallons

Mind you, these calculations are based on the assumption that all bedrooms in the house will be occupied. In case you live alone in a three-bedroom house, these calculations might not hold true.

  • Calculations by Water Usage

More often than not, the size of the septic system needed is based on the estimated daily water usage of a household. That’s because this is the most accurate way to calculating the septic tank size, since the main consideration while setting up a new tank is that it must be able to handle the amount of water that’s going to come its way.

Typically, the volume for a conventional septic tank is estimated at 1.5 times the average total daily wastewater flow. That said, in many places in the US, the minimum size for a septic tank is set at 1,000 gallons.

Listed below are the recommended septic tank sizes based on the expected daily water usage.

Daily Average Wastewater FlowMinimum Septic Tank Size
0-500 gallons per day900 gallons
601-700 gallons per day1200 gallons
801-900 gallons per day1500 gallons
1001-1240 gallons per day1900 gallons
2001-2500 gallons per day3200 gallons
4501-5000 gallons per day5800 gallons

You may also need to take into another factor, besides the number of bedrooms and the average daily wastewater flow, when installing a septic system — the local weather temperatures.

In some places, the local septic regulations specifically recommends that septic system sizes should be considered in view of the local climate. For instance, in extreme cold climates, such as Alaska, cold temperatures slows down the rate at which microbes break down the solid waste in the tank. Consequently, in these places, the septic tank needs to be bigger than normal to allow more retention of water at any given point in time.

Conversely, in places where the climate is very hot or warm, you may be able to make do with a smaller size septic tank. That’s because at high temperature the bacterial activity rates are much higher, or in simple words, the solid waste gets broken down more quickly.