A city sewer connection carries your wastewater through municipal pipes to a central treatment plant, and you pay a monthly charge while the city maintains the main. A septic system treats wastewater on your own property in a buried tank and drainfield, so there is no monthly bill, but you own every repair and pump-out.
How a city sewer connection works
A sewer connection is the simpler setup for a homeowner to live with. Wastewater leaves your house through a single pipe called the building sewer or lateral, then joins the city's public main running under the street. From there it flows by gravity, and sometimes pumping, to a wastewater treatment plant that cleans it before returning it to the environment.
You pay for this in two ways. There is a monthly sewer charge on your utility bill, and the city handles the treatment plant and the public main. The trade-off is that you give up control. You cannot decide how the wastewater gets treated, and the monthly fee continues whether you use a little water or a lot.
One point trips people up: the city does not own all of the line. In metro Phoenix, the property owner is generally responsible for the building sewer from the house to the public main. The city's responsibility typically begins at the main in the street. So a clog or collapse in the pipe across your front yard is usually your bill, not the city's. We cover this split in detail in our guide on who is responsible for the sewer line in Phoenix.
How a septic system works
A septic system keeps treatment on site. The U.S. Environmental Protection Agency describes a septic system as one that treats wastewater "close to the source," which is why these systems show up where public sewer pipes do not reach.
It works in two stages. First, all of your wastewater flows into a buried, watertight septic tank. Inside, solids settle to the bottom as sludge, grease and oils float to the top as scum, and bacteria break down some of the organic matter. The liquid in the middle, called effluent, flows out to the second stage.
That second stage is the drainfield, also called a leach field. The EPA describes it as a shallow, covered excavation in unsaturated soil. Effluent trickles out through the field, and the soil itself acts as the final filter, removing bacteria, viruses, and nutrients before the water reaches groundwater. The drainfield is the part you have to protect. If the tank is never pumped, escaping solids clog the field pipes, and the field can fail in ways that are expensive to fix.
Septic vs sewer: a side-by-side comparison
The table below lines up the two systems on the points that matter most to a homeowner.
| Feature | City Sewer | Septic System |
|---|---|---|
| Where wastewater goes | Municipal pipes to a central treatment plant | Buried tank and drainfield on your own property |
| Monthly cost | Ongoing sewer charge on your utility bill | None |
| Who maintains the main system | The city maintains the public main and plant | You own and maintain the entire system |
| Routine maintenance | Minimal for the homeowner | Inspect every 3 years; pump the tank roughly every 3 to 5 years |
| Big repair costs | City handles failures in the public main | You pay for tank, drainfield, and pump repairs |
| Where it is common | In-town and incorporated areas | Rural and unincorporated areas, often with a private well |
| What you must protect | The building sewer from house to main | The drainfield, plus the tank and what you flush |
The short version: sewer is low effort but a permanent line item on your bill, while septic costs nothing each month but hands you the maintenance and the risk.
City sewer wins on convenience. You rarely think about it. There is no tank to pump, no drainfield to protect, and when the public main has a problem, that is the city's crew and the city's budget. The downside is the monthly charge that never goes away, and the fact that you have no say in the treatment process. You also still own the lateral from your house to the street, so that section is on you.
Septic wins on cost over time, since there is no monthly bill. The catch is responsibility. You pay for pumping, and the EPA recommends a typical household have its tank inspected at least every three years and pumped every three to five years, depending on household size, tank size, and how much wastewater and solids you generate. University of Arizona Extension also points to a three-to-five-year pumping range for most homes. Skip that and you risk backups, sewage surfacing in the yard, or a failed drainfield. You also have to watch what goes down the drain. As the EPA puts it plainly, "Your septic system is not a trash can." Wipes labeled "flushable," grease, coffee grounds, and harsh drain cleaners either clog the field or kill the bacteria the tank depends on.
For pumping schedules specific to our climate, see how often to pump a septic tank.
Who has which in metro Phoenix
In most of the city of Phoenix and the surrounding incorporated towns, homes are on city sewer. The pipes are already in the ground, and a sewer charge shows up on the monthly utility bill. Septic systems are common farther out, in rural and unincorporated parts of Maricopa County, on larger lots, and on properties served by a private well rather than city water. Well and septic often go together, since a home off the public water main is frequently off the public sewer main too.
Not sure which one you have? A few quick checks usually settle it. A sewer charge on your utility bill means sewer; a $0.00 wastewater charge, or no bill at all, points to septic. You can also look for a septic access riser, a round black or green disc in the ground roughly 10 feet from the house, or a slight mound marking the drainfield. A rural address or a property with no city water meter, served instead by a well, also tilts toward septic. We walk through every clue in how to tell if you have septic or city sewer in Phoenix.
The responsibilities that come with each
Both systems leave part of the job in your hands, just different parts, and knowing where your responsibility starts and stops is what keeps a routine visit from turning into an emergency.
On sewer, your responsibility is the building sewer, the lateral line running from your house out to the public main. Keep it clear of roots and grease, and address slow drains before they become a full backup. Roots are the usual enemy here, since they seek out small leaks at pipe joints and grow into the line. The city takes over at the main in the street, but everything upstream of that point is the owner's to repair. A sewer hookup also still means watching what you put down the drain, since grease and so-called flushable wipes cause backups in a lateral just as readily as they do in a septic line.
On septic, you own all of it, and the duties are heavier. That means pumping on schedule, protecting the drainfield from heavy vehicles and deep-rooted plants, spreading out water use across the day so a heavy load of laundry or guests does not flood the tank, and watching closely what you flush. Solids that escape an overdue tank clog the drainfield pipes, and harsh chemicals or grease kill the bacteria the tank relies on to do its work. Keeping the access lids reachable and noting the date of each pump-out makes every future service call faster and cheaper.
Arizona adds one more duty at sale time. Under state rule, when a property with an on-site wastewater system changes hands, the seller must have it inspected within six months before the transfer, and a Notice of Transfer must be submitted to the county within 15 calendar days after the sale. In Maricopa County, that means the same six-month inspection window, a transfer notice, and a fee, with the tank typically pumped before the sale closes. This is a legal requirement, so confirm the current process with Maricopa County before you buy or sell a home with septic.
If you are unsure what is under your property or where your line runs, HQ Plumbing & Air can inspect it and lay out a plain maintenance plan for your home.