Safety rule: Never open or enter a cesspool, septic tank or seepage pit. They can hold toxic gases and may have weak or missing covers. Identifying, inspecting, abandoning or replacing one is work for qualified, licensed professionals under a local permit.
If you are shopping for a rural or older home, you may be told it has a “cesspool” and wonder whether that is just another word for a septic tank. It is not. A cesspool is an older, simpler design that regulators now treat as outdated, and in several states owning one can trigger a required upgrade when you sell, add a bedroom or have a problem.
This guide explains the difference, how to tell which one you have, and what two state agencies and the EPA say about when a cesspool has to be replaced. Rules differ widely by state and county, and some of the documents we read are several years old, so treat the examples as illustrations and check with your local health department before you act.
Cesspool vs septic tank at a glance
| Feature | Cesspool | Septic system |
|---|---|---|
| Basic design | A pit or buried chamber that receives wastewater and lets it seep into the ground | A septic tank, a distribution box and a soil absorption system (drain field) |
| Settling of solids | Happens in the same pit that leaches liquid | Happens in the tank before liquid moves on |
| Treatment | EPA calls it an outdated and ineffective method with no treatment | The tank starts treatment; the soil does the final treatment |
| Regulatory status | Rhode Island says new installations have been prohibited since about 1970; existing ones may have to be replaced when they fail, when the property changes hands or when flow increases, depending on the state | Standard permitted design, in many variations |
| Typical age | Older systems; Rhode Island says most systems approved after 1970 are not cesspools | Any age, including new installations |
What is a cesspool?
The Massachusetts Department of Environmental Protection describes a cesspool as a pit that acts as both a settling chamber for solids and a leaching system for liquids. Rhode Island’s Department of Environmental Management defines it more broadly: any buried chamber, such as a metal tank, a perforated concrete vault, a “beehive” or a covered excavation, that receives sewage from a building for disposal into the ground.
Washington State Department of Health puts it in terms of what is missing. Older systems were sometimes built with no septic tank for part or all of the wastewater. Untreated wastewater going directly into a bottomless tank is a cesspool.
The EPA is blunt about the result. In its description of community-scale systems it calls a cesspool an outdated and ineffective method of wastewater disposal with no treatment. It also lists a “straight pipe” that discharges raw wastewater into a nearby stream and says that practice is prohibited because of the severe health and environmental risks.
How a septic system is different
Massachusetts DEP describes a conventional septic system as a tank where solids can settle and begin to degrade, a distribution box, and a soil absorption system that further treats the effluent by removing some of the bacteria, viruses, phosphorus and nitrogen. In a cesspool, the same soil is asked to do all of the work. Massachusetts DEP says cesspools may overload the capacity of the soil to remove bacteria, viruses and phosphorus and to convert ammonia and organic nitrogen compounds.
That gap is the reason regulators prefer tank-and-field designs. For the full flow from house to tank to soil, see how septic systems work, and for the field itself see what a septic drain field is. For the many variations on the septic design, see types of septic systems.
Seepage pits and old tanks are not the same as cesspools
Washington’s health department lists two other outdated designs that homeowners sometimes confuse with a cesspool:
- Seepage pit. Wastewater first enters a septic tank and gets first-level treatment, then flows into a bottomless chamber that is usually several feet deep. The department says the oxygen needed for final treatment is not usually present at those depths, which allows untreated wastewater to discharge into the ground. It may meet the definition of a failure and need to be abandoned and replaced.
- Old septic tanks. The department notes that before the 1970s tanks could have been made from cinderblocks, wood, 55-gallon drums or concrete, manufactured or homemade, and that from about 1965 to 1975 single-compartment concrete or steel tanks were common. Metal tanks corrode and have been known to collapse. Older systems may need to be upgraded or abandoned and replaced.
So a house can have a tank and still have a system regulators consider outdated. The way to find out is through records and a professional inspection.
How to tell which one you have
- Check the age and permits. Rhode Island notes that regulations effective around 1970 prohibited new cesspools, so a system that received state approval after 1970 is most likely not a cesspool. See how to find septic system records.
- Look for the paperwork. A permit and as-built drawing should show a tank, distribution box and drain field if you have a septic system.
- Call the local health department. Washington’s health department says to contact your local health department to identify outdated systems and get advice on upgrades or replacement. In Massachusetts, the first contact should be the local Board of Health.
- Hire a qualified inspector if records are missing. Rhode Island says you may have to hire a licensed designer or registered inspector to decide whether you have a cesspool or a septic tank with a leach field. Its 2015 FAQ estimated inspection at $75 to $250, with an extra $150 to $200 if the cesspool needs pumping. Those are 2015 figures from one state, so treat them as a rough sense of scale.
If you cannot find the tank or pit itself, see how to find a buried septic tank.
When does a cesspool have to be replaced?
This depends on the state. The two state documents we read show very different approaches.
| State | When an upgrade is required | Source and date |
|---|---|---|
| Massachusetts | Not every cesspool must be replaced. Only cesspools that show signs of hydraulic failure, are extremely close to private or public water supplies, or otherwise fail to protect or threaten public health, safety or the environment need to be upgraded. Cesspools must also be upgraded before an increase in design flow, such as adding a bedroom | MassDEP Title 5 FAQ (citing 310 CMR 15.303); Title 5 version effective April 21, 2006 |
| Rhode Island | All cesspools are subject to the Cesspool Act of 2007 and will need to be replaced. A cesspool on a property sold or transferred with a closing date on or after January 1, 2016 must be removed from service within one year of closing. A failed cesspool must be replaced within one year of the failure, or sooner if there is an imminent threat to public health | RI DEM FAQ dated September 1, 2015 |
| Washington | Describes a cesspool as a system that may meet the definition of a failure and would need to be abandoned and replaced with a new septic system | Washington State Department of Health, Types of Septic Systems |
Rhode Island’s document adds more triggers. A cesspool serving a non-residential facility or a multifamily dwelling must be replaced as required under current state and EPA rules. A cesspool within 200 feet of the inland edge of shoreline features bordering tidal water, within 200 feet of public wells, or within 200 feet of a water body with a drinking water intake was due for replacement by January 1, 2014, and the FAQ says the remaining ones in those zones are in violation of the Act. The FAQ also says the law does not specify whether the buyer or the seller is responsible for the upgrade at a sale, only that it must happen within one year of closing, so it is a matter for negotiation. Because that document is dated 2015, check the current Rhode Island rules before relying on any date in it.
What counts as a failed cesspool?
Rhode Island lists five criteria, and says a cesspool can appear to be working and still be failed under them. A backup or surface leak is not the only sign. A cesspool is failed if any of these apply:
- It fails to accept sewage, shown by sewage backing up onto the ground or into the building.
- The liquid level is less than 6 inches from the bottom of the pipe that drains into it.
- It has to be pumped more than two times per year.
- It has been shown to have contaminated a drinking water well, stream or wetland.
- The bottom of the cesspool is below the groundwater table at any time of year, so the waste is in direct connection with groundwater.
Those criteria are specific to Rhode Island, but the warning signs overlap with those of any failing system. See signs of drain field failure and septic tank backup.
Replacing a cesspool: what the options are
Rhode Island’s FAQ says a cesspool must be replaced with a septic system, or the building must be connected to a sewer line if one is available. Massachusetts says that where a full upgrade of a failed system is not feasible, the local Board of Health may be able to approve a local upgrade as close to full compliance as possible, or a variance that may involve an innovative or alternative technology or a shared system. Washington says a cesspool may meet the definition of a failure and would need to be abandoned and replaced with a new septic system.
Some lots cannot take a conventional system. Rhode Island notes that very small lots, lots close to wells and water bodies, and other constrained lots may need more advanced systems with alternative technology, and in certain sensitive areas a system that reduces nitrogen. Those cost more than conventional systems. See types of septic systems and septic mound systems for examples.
What does it cost?
The only agency figures we could read are from Rhode Island’s September 2015 FAQ: an average of about $10,000 to $15,000 to replace a cesspool with a conventional septic system, and a typical $2,000 to $4,000 to tie in to a sewer, depending on distance, obstacles and re-plumbing. These are old and from one state, and costs have risen since, so do not use them as quotes. Current national ranges and the factors behind them are in septic system cost, and a sewer comparison is in septic vs sewer. Get written local quotes.
Help paying for it
Rhode Island’s FAQ describes low-interest loans through the state’s Clean Water Finance Agency for residents replacing a cesspool, available in municipalities that participate in a community septic loan program, so ask your town. Programs vary by state. Our septic system replacement financing guide covers loans, grants and other options.
Buying or selling a home with a cesspool
A cesspool is a reason to ask more questions, not an automatic reason to walk away.
- Ask what system the house actually has and ask for the permit and as-built. If the seller says “septic,” confirm there is a tank, distribution box and field, not a cesspool or seepage pit.
- Ask your local health department whether a sale, a new bedroom or an inspection triggers an upgrade in your area. In Rhode Island a closing triggers a one-year deadline. In Massachusetts a bedroom addition does.
- Get a qualified inspection that identifies the system type and its condition. See septic inspection when buying a house and septic inspection cost.
- Budget for replacement and negotiate who pays, since Rhode Island leaves the question to buyer and seller.
- If you are selling, see selling a house with a bad septic system for disclosure and repair options.
A tank with no outlet that is emptied by a pump truck is a different thing from a cesspool. See septic holding tanks for when rules allow one.
Frequently asked questions
Is a cesspool the same as a septic tank?
No. A septic system has a tank where solids settle, a distribution box and a drain field. A cesspool is a pit where settling and leaching happen together, and the EPA describes it as an outdated and ineffective method with no treatment.
Are cesspools illegal?
Rhode Island says rules effective around 1970 prohibited new cesspools, and states require existing ones to be replaced under certain conditions, such as failure, sale or a bedroom addition. Whether you may keep a working one depends on your state and county.
Do I have to replace my cesspool when I sell my house?
In Rhode Island, yes: the Cesspool Act requires a cesspool on a property being sold to be removed from service within one year of closing. In Massachusetts, only failed cesspools or those near water supplies need to be upgraded, and a bedroom addition also triggers one. Check your local rules.
How do I know if I have a cesspool?
Look at the permit and as-built drawings, and note the age. Rhode Island says a system approved after 1970 is most likely not a cesspool. If records are missing, a licensed inspector can tell.
What does it cost to replace a cesspool?
Rhode Island’s 2015 FAQ gave about $10,000 to $15,000 for a conventional septic system, with higher costs for constrained lots. That is an old figure from one state, so get current local quotes.
What is a seepage pit?
Washington State Department of Health describes a seepage pit as a bottomless chamber that receives liquid from a septic tank. It may fail to treat wastewater because oxygen is usually not present at those depths.
Sources and further reading
- U.S. EPA: Types of Septic Systems
- Washington State Department of Health: Types of Septic Systems (Outdated Systems)
- MassDEP: Title 5 / Septic Systems FAQ (hosted by the Town of Acton)
- Rhode Island DEM: Cesspools and the Rhode Island Cesspool Act FAQ, September 1, 2015 (hosted by the Town of Coventry)
This article provides general U.S. homeowner information based on federal and state agency material, some of it dated. Cesspool rules, deadlines, inspection requirements and costs vary by state, county and site. Always follow your local health department’s requirements and the advice of a licensed local septic professional.