Aerobic septic “all in one” with caved in pump tank chamber

Here is an aerobic “all in one tank” system that has the pump tank compartment caved in. Looking into the lid of the pump tank chamber you can see that the concrete wall has been pushed in so that it is visible through the opening.  The normal position of the sidewall is out of view when looking into the lid opening.


This view is of the outside of the tank with some of the dirt from the side area removed.  You can see directly into the pump tank chamber.


I am not exactly sure what forces were at play when the side caved in but it may not have happened if there was steel reinforcement embedded in the concrete.


This is what it looked like after the new 500 gallon concrete pump tank was installed. The 4″ pipe coming out of the aerobic chamber was plumbed to the new pump tank with 1/8″ per foot slope.  The electric for the pump and the 1″ PVC effluent line were connected to the existing system and it was inspected with a PASS.



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HiBlow 80 linear air compressor diaphragms

The HiBlow 80 (HP-80) is a very popular linear air compressor that is used on 500 gallon per day (GPD) aerobic treatment units (ATUs). It has the potential to be rebuilt which can save the owner money by not having to replace it when internal parts break.  Here are two pictures with the first being that of a torn diaphragm and the second being that of a new undamaged diaphragm.  The rebuild kit comes with two diaphragms also called “chamber blocks” which are intended to both be replaced at the same time.

Notice the tear in the black rubber on the right hand side of the round part.  This is where the rubber failed and what caused the air compressor to stop pumping air.


The below picture is of the new diaphragm or chamber block.


Here is a link to the manufacturer’s video.


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Liberty cast iron effluent pump 1/3hp

This is a 1/3H.P. cast iron effluent pump. There are multiple manufacturers of this type of pump and this is just one of them.  There is a difference between this type of cast iron pump and the type of pump that you would purchase from your local home improvement store.  This is not just a sump pump but rather a wastewater effluent pump.

Liberty cast iron effluent pump 1/3hp.

Liberty cast iron effluent pump 1/3hp.


Chlorine tablet example

There are many manufactures of chlorine tablets that are specifically designed for septic system disinfection. These are not the same tablets that you use in your swimming pool.  These tablets are designed to dissolve fast with little contact time with the wastewater.

Norweco Tabs 25

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HiBlow 80 linear air compressor

This HiBlow 80 is a very popular linear air compressor used on many 500 gallon per day (GPD) aerobic treatment units (ATUs). It has the potential to be rebuilt which can save the owner money by not having to replace it when internal parts break.

HiBlow 80 linear air compressor

HiBlow 80 linear air compressor

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Air diffuser examples

Air diffusers are pieces that go down below the water surface in the aerobic treatment unit (ATU) and diffuse the air that the air compressor pumps in.  The purpose of the diffuser is to break the air down into smaller bubbles so that there is more surface area for the oxygen that is in the air to absorb or diffuse into the water and become dissolved oxygen (DO).  This DO is what the aerobic bacteria need to survive in order to consume the waste.  Here are a couple of examples but there are many other shapes and sizes.

ProFlo air diffuser for 500GPD ATU.
Air diffuser


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Aerobic septic system

Many folks have a type of septic system that is commonly referred to as an “aerobic septic system” which uses a mechanical air pump to insert air into a tank or chamber which is referred to as the aerobic treatment unit (ATU).  This form of aerobic treatment is referred to also as secondary treatment.  This secondary treatment usually takes place in an ATU which is installed after the pretreatment tank and hence the name secondary treatment.  This secondary treatment which utilizes aerobic bacteria is a very effect method for breaking down waste but it does not make the effluent safe for human contact.  When the effluent leaves the ATU it has been through the secondary treatment process and it is typically a clear liquid with a slight odor but it still must be disinfected to an acceptable level in order to be deemed safe for contact with humans.  In some cases the effluent that leaves the ATU is filtered and then pumped through drip tubing for subsurface disposal and may or may not need to be disinfected first. After the effluent leaves the ATU and it is disinfected it is then stored in a pump tank for disposal.  There are many different brands and configurations for this type of aerobic septic system.  It is typical for smaller residential systems to have three tanks or a single tank with three chambers.  The first chamber is the pretreatment tank, the second is the ATU, and the third final chamber is the pump tank chamber.

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Conventional Septic Systems

There is no one configuration that describes a conventional septic system perfectly. The conventional septic system has evolved over time as a way to process waste water whether it is from a commercial establishment or a residential location. Depending on the age of the septic system it will most likely contain characteristics based on the standard practices that were prevalent at the time that it was installed. Conventional septic systems that were installed before there was local regulation in place could be made up of almost anything. Once the need for regulation was identified there was most likely already the practice of using single or double 500 gallon concrete tanks. The multiple 500 gallon concrete tank configuration with a gravity fed subsurface leaching field is widely used still to this day.

Wikipedia has this explanation for “septic tank”

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