The septic air compressor/air pump is one of the most important parts of your septic system. The system cannot work the way it was engineered to without the air pump working. The septic air pump has two purposes.
First, the air pump puts oxygen into the water, creating dissolved oxygen which allows for the growth and survival of the aerobic bacteria. The aerobic bacteria are what part up all of the waste in the tank. Most of the bacteria in the tank can also be found in your body. These particular bacteria are much larger and process waste more efficiently than the anaerobic bacteria found in a conventional septic system.
Second, the air pump creates flow in the tank that mixes and breaks down large solids into tiny particles. This makes it very easy for the bacteria to attach to and eat the waste.
If your air pump quits working in your aerobic system, your system will convert to anaerobic over a period of about 4-5 days. It actually happens faster as to reduce the nitrogen produced by the bacteria. If you turn the aerator off in some systems for a period of time, the dissolved oxygen is removed and your system converts to anaerobic in 4-6 hours. The biggest problem with this happening is that in some states there is no trash tank required and no secondary treatment system behind your aerobic system. Once the aerobic system turns back anaerobic, instead of producing a clean odorless discharge the effluent will be closer to raw sewage. As you may realize, raw sewage discharging into a ditch, lake, or pond, or being sprayed on your lawn is not a good thing. If you have a spray system, your lawn will start to smell of sewage after 5–6 days. I doubt your neighbors will appreciate it.
Size Does Matter
One common misconception is that it doesn’t matter what size of pump you use as long as air is getting into the water. Well, you couldn’t be more wrong about that. Air pump sizing is important to the operation of your system. Not every system will use the same size air pump. Pump size is determined by the size of your system in Gallons Per Day (GPD) in conjunction with the square footage of your house and how many bedrooms/bathrooms you have. Every state is different but most guidelines and rules are similar. If you have been to the different websites, then you already know there are many different types and sizes. The air pump size is normally determined by the volume capacity of the tanks, the style of air diffusers in the tank, and how many GPD the system is designed to treat.
Using the wrong pump could create multiple issues with your system. More sludge could transfer to the pump tank, shortening the life if your effluent pump. Biomaterial building up in your field lines is another issue. More trash in your sprinklers or field lines could be damaging to the field lines. Field lines or leach fields can cost thousands of dollars to replace. We have charts and cross-reference guides to help you make the right choice.
Bigger is not Better
Some people think that bigger is better. Aerobic Septic Systems experience diminishing returns just like anything else. Systems are sized based on the area of water in the tank and how much dissolved oxygen is needed to treat the water or influent entering the tank. So a larger air pump will not give you better treatment. Bigger is better for large municipal systems, but this also requires specifically placed diffusers. Home systems are simply too small to upscale size like that.
Types of Aerators (Septic Air Pumps)
Linear Septic Air Pumps
Linear septic air pumps or aerators are the most common air pump on the market today. They are quiet, energy efficient, and easy to service. Not all linear septic air pumps are of the same quality or durability. Hiblow, FujiMAC, Secoh, and SSP/Septic Sewage Pumps top the list for proper operational air flow rates and for working under hot temperatures. Hiblow is the inventor of this style of diaphragm air compressor and most others are replications of their design. FujiMAC is the exception. FujiMAC’s MACII is probably the most efficient pump on the market and carries with it the market’s longest warrant. A 2-year warranty is incredible for a septic aerator and some dealers even offer 3. All of the other products look suspiciously like a Hiblow when you open the box. However, it’s what’s on the inside that counts. Hiblow and FujiMAC use higher quality motor coils and diaphragm material. We can say this with certainty after years in the field and seeing thousands of pumps. The linear diaphragm pumps have some weaknesses compared to their rotary vane counterparts. Diaphragm pumps don’t do well under high back pressure; the diaphragms will fail prematurely. They will also not run for as long as rotary vane pumps. You can only expect 2-4 years of lifespan in hot, southern climates, and 3-5 in northern states. FujiMACs should last for 3-5 years in the south and 4–6 in the northern states. Due to its rare-earth magnet and housing design, the FujiMAC runs much cooler; extending the life of the pump. You can find some of the pumps still running after 8-9 years, but it’s uncommon. Kits to rebuild these pumps are relatively inexpensive. Hiblow rebuild kits are $65, Secoh $79. In our experience working with these diaphragm air pumps, you get what you pay for. Some pumps are more because the manufacturer charges more. In order to avoid cheap performance from a cheap pump, be mindful of the application in which the air pump will be serviced.
Rotary Vane Septic Air Pumps And Aerators
Rotary vane septic air pumps are manufactured in different sizes. The only companies that make these for the septic industry are Gast and Thomas. Gast has the lion’s share of the market with at least 80%. Gast’s and Thomas’s vanes are interchangeable in some models and are identical to one ten thousandths of an inch in others. The rotary vane pump is the longest lasting and most hassle-free pump you can buy. Some Fast AT05, 0523, and Thomas models have been running for 15 years and counting.
The vane material is, for lack of a better phrase, one of mankind’s greatest accomplishments. Wearing out at a rate of 1 thousandth of an inch every 1.25 billion rotations. The pump will spin 2.5 billion times a year and won’t need service until at least the 6-8 year mark. The downsides to rotary vane pumps are their power usage and volume. Gast has gone to great lengths to quiet them down in recent years and we’ve definitely noticed the difference. We’ve seen pumps that received no cleaning and no service for 9 years. With a simple cleanout they ran for a few years more. You can then rebuild it and it runs like new. After two rebuilds you’ll notice the bearings probably giving out but that’s still a lot of value from one pump. Another downside to rotary vane pumps is the prohibitive cost; $475 for a GAST AT05 vs $265 for a Hiblow HP-80. Think of these kinds of pumps as a Toyota, they run and run. You get what you pay for here.
Shaft Style Aerators
Shaft style aerators were the first type of air pump to be used in a residential application. Manufacturers Jet and Norweco still use these types of pumps in their systems. These pumps are only sold through Jet and Norweco to their dealers. They can also be directly exchanged by the homeowner for a replacement. There are imitations of these pumps that are pretty reliable, there was a need in the market for alternative shaft aerators. The web is a powerful thing, and about 3,000 knock-offs are sold each year to installers and homeowners. Sometimes these aerators can have a fragile system, though. If the system floods it usually fries the whole thing. If hair gets wrapped around them, they’ll also fail. The systems themselves are also hard to work on, and workers may refuse to service some Norweco models simply because of how difficult it is to service some areas of it.