A lift station moves sewage: it collects wastewater in a wet well and pumps it uphill to a gravity sewer or force main. A septic tank treats sewage on site, settling solids and sending the liquid to a drainfield. One is transport, the other is treatment. Some septic systems add a pump tank, which works like a small lift station.
What does a lift station do?
It moves sewage uphill when gravity can't. Sewers work by slope, and when a building or a neighborhood sits below the sewer it needs to reach, the sewage has to be pumped. The EPA's pressure sewer fact sheet explains that the slope needed for gravity flow "may require deep excavations in hilly or flat terrain, as well as the addition of sewage pump stations."
A lift station has four basic parts:
- 1A wet well, the tank where incoming sewage collects.
- 2Pumps, usually two, that start when the level rises.
- 3Level controls (floats or sensors) that turn the pumps on and off.
- 4An alarm that warns when the level gets too high.
Inside a single building, the smaller version is a sewage ejector. The plumbing code covers it in Section 712.1: drains "that cannot be discharged to the sewer by gravity flow shall be discharged into a tightly covered and vented sump from which the liquid shall be lifted and discharged into the building gravity drainage system by automatic pumping equipment." Our page on what a sewage lift station is explains the parts in more depth, and sump pump vs ejector pump vs lift station sorts out the sizes.
What does a septic tank do?
It starts treating sewage where there's no sewer at all. The EPA says the septic tank "digests organic matter and separates floatable matter (e.g., oils and grease) and solids from the wastewater." Solids settle into sludge, grease floats as scum, and the clearer liquid in the middle, called effluent, flows out to the drainfield. There, the EPA says, the soil "accepts, treats, and disperses wastewater as it percolates through the soil, ultimately discharging to groundwater."
A standard septic system uses no pumps at all. Water runs downhill from the house to the tank and from the tank to the drainfield. See septic tank vs leach field for how the two halves work together.
How do they compare side by side?
The core difference is transport versus treatment:
| Lift station | Septic tank | |
|---|---|---|
| Job | Moves sewage to a higher sewer | Treats sewage on site |
| Where the sewage ends up | A city or district treatment plant | The soil under the drainfield |
| Needs power | Yes, for the pumps and alarm | No, for a standard gravity system |
| Main parts | Wet well, pumps, controls, alarm | Tank, baffles or outlet tee, effluent filter, drainfield |
| Main risk | Pump or power failure, which leads to backups and overflows | Solids or grease clogging the drainfield |
| Arizona rules | ADEQ sewage collection permit when it serves more than one dwelling | Arizona on-site wastewater rules |
### What are the Arizona rules for each?
They come from different parts of the state's wastewater rules. A lift station is part of a sewage collection system. Arizona's general permit for collection systems, R18-9-E301, applies to "A sewage collection system that includes a force main or lift station serving more than one dwelling." For those systems the rule requires, among other things, that the owner "Equip a lift station wet well with at least two pumps," that "The lift station is capable of operating at design flow with any one pump out of service," and that high or low levels "trigger an audible or visible alarm." See whether a private lift station needs an ADEQ permit.
A septic system is an on-site wastewater treatment facility, covered by a different part of the state's wastewater rules. Maricopa County says the easiest way to make one last is "to routinely pump the tank every three to five years, not dump unapproved products into the system, and clean the effluent filter inside the tank every six to twelve months."
Where do lift stations and septic tanks overlap?
In a few kinds of systems that use both a tank and a pump:
- Septic systems with a pump tank. When the drainfield sits uphill from the tank, or the soil needs even dosing, the effluent goes to a second chamber with a pump. The EPA's low pressure pipe fact sheet describes it: effluent "flows by gravity from the tank to a pumping chamber, where it is stored until it reaches the level of the upper float control, which activates the pump." That pump chamber is a small lift station for septic effluent. Maricopa County lists "pressure distribution" among the alternative systems it sees.
- STEP sewers. Some communities collect sewage with a septic tank at each property and a pump that sends only the liquid to a pressure sewer. The EPA says "In STEP systems, wastewater flows into a conventional septic tank to capture solids." The septic tank does the settling, and the pump does the lifting.
- Grinder pump sewers. The opposite approach: there's no septic tank, and a grinder pump chops the solids and pumps everything into the sewer. The EPA says "GP systems do not require a septic tank."
So a property can have a septic tank with a pump, or a pump with no septic tank. What decides which it is: whether the sewage is treated on the lot or sent away.
What happens when each one fails?
They fail in different ways, and both are unpleasant.
A lift station fails fast. If the pumps stop or the power goes out, the wet well fills and sewage backs up into the lowest drains or overflows at the station. The EPA warns that "Power outages can result in overflows if standby generators are not available." That's why the alarm matters, and why Arizona's permit rule requires a second pump. If an alarm is sounding now, see what to do when a lift station alarm goes off.
A septic system fails slowly. Solids and grease build up, get past the tank, and seal the drainfield soil. Maricopa County says poor maintenance "can cause solids or greases and oils in the tank to migrate into the drain field and clog the system." The EPA notes an overloaded drainfield "can flood, causing sewage to flow to the ground surface or create backups in toilets and sinks." See signs your septic system is failing.
Not sure which one your property has? Our page on whether you're on septic or city sewer in Phoenix walks through how to check.
HQ Plumbing & Air repairs and replaces the building drains and sewer lines that feed both systems across the Phoenix area, and clears backups on homes and businesses. We're licensed and insured, with free estimates and upfront pricing. See our commercial plumbing services.
A lift station moves sewage uphill. A septic tank treats it where it lands. Some systems need one to feed the other.