Aerobic Treatment Unit Septic Tank Sizes:

Here we provide the size and design requirements for aerobic septic tanks or ATUs.

Here are designs and products for aerobic septic treatment units (ATUs, or in the UK, Australia, New Zealand, Aerobic Wastewater Treatment Units or AWTs) for onsite waste disposal, also called fine bubble aeration systems.

We address aerobic septic system design, features, inspection, repair, and maintenance.

Aerobic septic system product sources are also listed. Qualified aerobic septic tank designers, producers, or service providers may be listed at this website at no fee. The page top illustration of a four-chamber aerobic wastewater treatment unit is adapted from the New Zealand Taranaki Regional Council's sewerage system guide.[5]

Aerobic Treatment Unit Tank Size Requirements

Typically a residential aerobic septic treatment unit does not run continuously, just as inflow to it is not continuous.

ATU size or capacity is determined as for a conventional septic system, by allowing 50 to 100 gallons of wastewater per day per building occupant.

Some jurisdictions require that the system minimum capacity accept 500 gallons of wastewater daily.

Safe aerobic treatment tank size advice

A "safe" design size for an aerobic treatment tank that allows for temporary power outage (and thus loss of the aeration pump) is an aerobic treatment tank at least as large as the conventional tank that would have been required for a given site.

Aerobic treatment tanks in cold climates

If your ATU tank is being installed in a cold climate, it may be necessary to insulate the treatment tank (use 2" solid foam panels) to keep the tank temperature high enough (above 54 degF) for the aerobic processing to continue in cold weather. (Some thermophilic microorganisms require temperatures as high as 131 to 149 degF.)

ATU Flow: Continuous or Intermittent Aerobic Pumping Systems

Design Alternatives for Aerobic Septic Systems

Two basic ATU designs provide for intermittent or continuous flow through the system.

Intermittent flow aerobic septic systems

Just as most residential septic systems do not receive wastewater continuously but rather intermittently, the ATU may be designed to turn the aerator and agitator on and off as needed. Intermittent flow septic systems, including aerobic or aeration treatment designs are also called a "batch system" septic design approach.

Continuous flow aerobic treatment system designs

Other aerobic or aeration septic treatment systems, particularly aerobic systems which have to serve a larger facility where wastewater inflow may be continuous, may themselves operate continuously. Obviously these designs are called "continuous flow" aerobic treatment systems.

How to Select & Where to Buy an Aerobic Septic Tank Aerator Pump

Question: How do I size the correct aerator pump for my ATU ?

11/5/2015 Josh said:

How do I size the correct aerator pump for my ATU ? My systems holds 600 gallons . There are 5 people in our house , with vistors sometimes 10 ?

Do I need a dual pump or can I run pumps alternately ?

Reply:

Josh

In very general terms, the ATU size or capacity is determined as for a conventional septic system, by allowing 50 to 100 gallons of wastewater per day per building occupant.

Indeed a number of aerobic septic designers suggest dual aerator pumps that are run alternately to be sure that both are operational. That design helps assure that the ATU can keep operating even if one of the pumps fails and thus needs repair or replacement.

Please see detail on aerobic pump sizing

at AEROBIC SEPTIC AERATOR PUMPS - next in this article series.

 

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2018-12-03 by (mod) - All levels are good but alarm is on

David

SEPTIC ALARM TROUBLE SHOOTING

At

https://inspectapedia.com/septic/Aerobic-Septic-Alarm-Diagnosis.php

Should help.

Keep me posted

On 2018-12-02 by David

All levels are good but alarm is on

On 2018-05-26 by (mod) - required by code to upgrade any portion of the septic system when increasing occupancy?

It's not likely that that the septic tank, nor the effluent dispersal system will be adequate.

Review your system capacity with the manufacturer of your specific aerobic system or a local septic engineer.

Surely you need a building permit.

On 2018-05-26 by Scott Sears

We are currently in the planning stages of building a detached garage with an in law suite. We will be adding a shower,toilet and lav.

We have an aerobic drip system with a 750 gallon tank and aprox 2250 linear feet of drip line.

There would be a total of 6 people in home, would it be required by code to upgrade any portion of system and would our current system be sufficient enough to handle 6?

On 2017-12-19 by Allen

How long should you let your sprinkles run on an average day of use?

We approximately use 160-170 gallons of water a day.
Do the sprinklers and system freeze and if so at what temperature?

On 2017-09-22 by (mod) -

Thanks for asking, Dexter. To have space and include references I repeat your question and give a detailed answer at the bottom of the article above. You may need to clear your browser cache and it may take 24 hours for the new article contents to appear on your server.

Take a look and let me know if you have more questions.

On 2017-09-21 by Dexter

How do you check the air pressure on a pump to make sure your diffuser is not clogged what should the air pressure reading be

On 2016-03-11 by (mod) - aerobic septic tank aerator pump

Carol,

If you are asking about an aerobic septic tank aerator pump, check the owner's manual for your particular aerobic system as some designs vary, but generally the aerobic pump is on all the time. The pump is needed to aerate the system to keep it working.

If you are asking about a sewage pump or effluent pump, the pump should be operating based on a float not on a manual on-off switch.

On 2016-03-11 by (mod) -

RE-Posting

AUTHOR:carol (no email) 2016/03/10

COMMENT:is it better to leave a septic tank pump on permanently or just switch it on for a little while periodically to empty excess water then switch off.

On 2015-11-06 by (mod) - How do I size the correct aerator pump for my ATU ?

Thanks for asking, Josh.

I've written a detailed reply at

https://inspectapedia.com/septic/Aerobic_Septic_Tanks.php#ATU_Pumps

Basically you need a 4-5 cfm pump

On 2015-11-05 by Josh

How do I size the correct aerator pump for my ATU ? My systems holds 600 gallons . There are 5 people in our house , with vistors sometimes 10 ?
Do I need a dual pump or can I run pumps alternately ?

...

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Citations & References

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