Aerobic Treatment Unit Septic Tank aeration pumps.

This article series provides the size and design requirements for aerobic septic tanks or ATUs and aeration pumps. 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]

Page top image: a Secoh EL 80-17 diaphragm pump used on aerobic septic systems and discussed in this article.

Aerobic Treatment Unit Aerator Pump Requirements

Types of Septic Air Pumps

• Diaphragm type aerator pumps are perhaps the most-widely-used on residential aerobic septic systems - or:
• Linear air pumps for aerobic septic systems, use diaphragm or pistons to compress and pump air.
  
  Example brands: HiBlow, Medo, Thomas brands, also Cyclone, Secoh, Alita air pumps.
• Rotary-Vane air Compressor air pumps for aerobic septic systems use spinning carbon steel vanes that compress air. Durable, higher electricity use, louder than linear air pumps.
• Regenerative Blowers used for aerobic septic systems are used on Hoot septic systems, Fast septic systems, and Bio-Microbics systems. These pumps are typically switched on and off under control of a timer. They are not run continuously.

Typical Aerobic Septic Air Pump Capacity Ratings

Aerobic septic air pumps are rated in output as cubic feet per minute (CFM) or liters per minute (LPM) of air.

A typical septic aerator pump might run at 5 CFM or 80 LPM of air output. The typical range of septic air pumps for residential septic systems is about 2 to 8 cfm or from about 40 to 200 LPM of air.

Indeed there is something tricky to understand about these ratings. A septic air pump rated for 100 LPM air output at "open flow" (or un-restricted output) will actually deliver a lower flow rate when the output is restricted such as by having its outlet six feet deep in a septic tank.

SO: if you had a tee in the pump's output air line that runs between the pump's output port and the aerobic septic tank diffuser, you WOULD see some air pressure if you put a gauge on that tee (with appropriate fittings of course - you can't just hold the gauge there).

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 visitors sometimes 10 ?

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

[Click to enlarge any image]

Reply: aerobic septic pump sizing table

Josh

Perfectly reasonable question - I don't know.

The proper aerator pump size or cfm of air delivery needed depends on at least these variables, all of which add up to "ask your aerobic septic designer or aerobic pump sales or supplier contact":

• the specifics of how your particular system was designed, which varies by manufacturer and model.
• the average and maximum daily wastewater flow into the septic system
• the septic tank size
• the design of the actual aerator or bubbler
• the distance from aerator pump tank, the piping size or diameter, length, and restrictions such as number of elbows
• the depth of the bubbler - the vertical distance down which the aerobic pump must force air and thus the psi resistance it will encounter

If you cannot find any manufacturer name on your pump then we fall back to generic advice:

The aerator pump size (and thus its capacity to bubble) is chosen to match the average wastewater flow into the septic tank per day.

In the article AEROBIC ATU SEPTIC TANK SIZES we suggest

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.

Below I've cobbled up an aerobic septic tank aerator pump sizing table.

Notes to the table above

cfm = cubic feet per minute

gpd = U.S. gallons per day

lpd = litres per day

lpm - liters per minute or in the U.K. litres per minute

We recommend checking to assure that the aerobic pump you select is approved by the NSF (National Small Flows) for your system.

You can estimate your daily wastewater usage more accurately

from SEWAGE FLOW & DESIGN FLOW ESTIMATES and use your browser "back" button to return here.

Also see AEROBIC ATU SEPTIC TANK SIZES to check the size of your aerobic treatment unit (septic tank)

Watch out: A review of companies selling aerobic septic system aerator pumps (November 2015) found both OEM as well as alternative pump models and brands widely available. Check with the designer or manufacturer of your specific aerobic septic system as manufacturer's specifications may vary from this general table.

Watch out: do not simply add-on an aerator or agitator to a conventional septic tank to "convert your septic tank to an aerobic system".

Making this change alone without other critical design changes such as outlet filters or a settlement chamber may agitate the sewage in the septic tank causing solids to flow into the septic drainfield or absorption bed - causing its rapid desctruction through clogging.

Aerobic Septic System Air Pump Specifications

Question: How do you check the air pressure on an aerobic septic air pump?

2017/09/21 Dexter said:

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

Reply: aerobic septic air pumps are rated as open flow in CFM or LPM but air pressure readings can be diagnostic

Thanks for asking, Dexter.

There is not a single "right answer" to the question of what should be the air output for an aerobic septic system air pump (also referred to as septic aerator pump or septic diffuser pump, or septic air pump or septic "compressor" pump).

That's because depending on the septic tank size and daily waste flow, the pump model will be chosen to match with a particular output rate.

Septic air pumps are typically rated not by an air pressure - because the pump is designed so that its output end is open to water and ultimately to the atmosphere. It isn't designed to be pumping into a closed container - which is what you'd need to measure air pressure.

Put another way, though the aerobic air pump has a pump operating air pressure capacity, the pump output is normally going to be described by the manufacturer as "open flow" capacity in CFM (or LPM).

When a septic air pump is running in open flow its output is actually at 0 psi.

That's why I said you can't easily measure it.

What Air Pressure Could be Seen at a Septic Air Pump?

Using a Hiblow HP-80 aerobic septic air pump as an example, that pump's maximum airflow is rated by the manufacturer as 4.2 cfm (119 LPM) WHEN THE PUMP IS OPERATING AT at 0 p.s.i., and the rated air flow will be LOWER - about 80 LPM (2.83 cfm) when under actual installed-conditions the pump is operating at the rated pressure of 2.13 p.s.i.

Because individual septic air pump specifications will be different among manufacturers' brands and models even before the pump is installed, you want to make a note of your pump's specific brand and model.

Then from the manufacturer you (or we) could obtain their expected pump air flow rates at open conditions and their expected pump air flow rates at typical installed conditions.

Most likely the range will be between 1.5 and 5 psi. Why? Well if we went under water (I don't want to swim under sewage) down to 30 feet, we would be at one ATM of pressure or about an additional 14.6 psi of pressure from being on the ground at sea level.

If we figure that your septic tank is maybe 4 or 5 feet deep (of sewage) then we are at 5/30 or 1/6 of 1 ATM. 1/6 of 14.6 psi = 2.4 psi.

So you can see that we don't need huge pressures to push air down to about five feet of depth.

IF at our magic Tee that we installed in the air line we saw pressures lower than specified by the manufacturer the pump is probably defective (or there's an air leak). If we see pressures creeping UP from what the manufacturer specifies then the diffuser may be clogged.

But it's easier to skip the tee and the pressure gauge and look for bubbles.

Question: what are the aerobic septic pump tubing or piping distance limitations?

Illustration, aerobic septic aerator pump air flow capacity in CFM or LPM performance curves for the Secoh EL-series aerobic pumps illustrates the reduction in net air flow or CFM as a function of pressure increase in the delivery system over zero restrictions at the pump outlet. - adapted from Secoh, cited in detail below.

[Click to enlarge any image]

2019/02/18 Bill Grambsch said:

I want to move my Aeration air pump 50 feet away from my septic tank. I have 50 ft of 1/2 PVC tubing and power to run the air pump.

I want to move the air pump to the back of my house and place it in a vented soundproof enclosure.

Any issues or concerns? I have an EL-80 air pump producing 3.6 PSI. Any reason I can not add 50 ft of air hose to get rid of the noise.

Reply: keep aerobic air pump tubing or pipes as short and straight as possible or risk inadequate aerobic treatment and system failure

Bill,

Thank you for asking an interesting question:

What is the effect of distance on aerobic septic tank aerator pumps? or What is the permitted tubing length or distance for an aerobic septic aerator pump?

The Secoh EL-80 septic pump is sold in several models and ranges in CFM or LPM of air delivery rated as Air Flow: 80LPM or 2.83 CFM 4.23 CFM Open Flow.

The Secoh aerator pump performance curves shown below (extracted from the company's sales literature) makes clear that as the pump "PSI" increases the flow rate decreases. The pump ratings are given as "open flow" rate.

That "open flow" is critical to understand. Open flow is measured right at the outlet of the pump with no resistance on the pump.

Increases in tubing length, number of elbows, bends or fittings, as well as any increase in depth to which the pump has to push air all will decrease the actual measured air delivery volume at the aerator in the aerobic septic tank.

septicsolutions a vendor of septic aerators sums up the problem nicely as:

The air pump size is normally determined by the volume capacity of the tank, the style of air diffusers in the tank, and how many GPD (Gallons Per Day) the system is designed to treat. - www.septicsolutions.com

Watch out: What that means is that IF we can assume that your septic aerator pump was properly sized and installed in the first place, you should not move it 50 feet away before consulting with Secoh or with the company who designed and installed your aerobic septic system.

You may need to use larger diameter tubing or a higher capacity septic pump to assure adequate delivery of air into your aerobic septic tank.

Watch out: if the air flow rate, volume, duration, or CFM / LPM in an aerobic septic tank is inadequate the cost can be ruinous: failure to adequately treat the septic waste risks early failure of the septic drainfield and contamination of the nearby environment.

I'm sorry I can't give a more specific answer like - yeah ok if you go to 3/4" tubing - because like Secoh, from my distant perch here in central Mexico I can't see your aerobic septic installation and have no other details about it.

The supplier septicsolutions can be reached at 1-877-925-5132 or sales@septicsolutions.com Septic Solutions, 314 Center St., Dieterih IL 62424 USA

Here is what Secoh says about the piping requirements for their air pumps:

PIPING: Select tube size, lengths and accessories to keep pressure loss as small as possible.

USE: Straight piping and as short as possible

Tubing, which diameter is bigger than the port of the unit (inside diameter min. 19mm).

Large radius bends and no elbows

Valves of bigger diameter than the blower’s connector port

Smooth-running valves that provide the lowest pressure drop

Low air loss diffusers for aeration

- Source: Secoh EasyPump, 50 West Drive, Melbourne, Florida 32904 United States Tel: 321-253-1999 1-800-225-4498 Email:
sales@easylift.com Website: www.secoh.us.com or store: store.secoh.us.com retrieved 2019/02/18 original source: store.secoh.us.com/installation-operation/

Other aerobic septic system aerator-air pump checks you can make

Check that

1. That the aerobic aerator pump is running
2. That the aerator pump is delivering air to the septic tank - air bubbles are appearing at the tank top inspection port.
3. That the aerator pump tubing or piping is not constricted, bent, kinked, or clogged with debris
4. That you are performing the period maintenance for your aerator pump as recommended by the manufacturer - examples of those aerobic pump maintenance and installation guides are included below.
5. Some septic air pump models include an alarm feature to let you know if the pump is off or not working. That's a nice feature since if you leave your aerobic system without its aerator it is not working, it is not treating sewage adequately, and in as little as a few days the system can fail.

Aerobic Septic Pump Sources

This information moved to AEROBIC SEPTIC AERATOR PUMP SOURCES including aerobic septic pump sources, manuals, technical guides

...

Continue reading  at AEROBIC SEPTIC AERATOR PUMP SOURCES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

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