What You Should Know About Septic Systems in Rhode Island
About This SeriesWelcome to Know Your Home, our series on the practical side of homeownership. Buying and selling are only part of what it means to own a home. Just as important is understanding the house itself: how it works, what it needs, and what questions are worth asking along the way. Last month we covered what you should know about radon. This month, we head underground.
Out of sight, but keep in mind!
One of the most essential and potentially costly systems in a home is one that is rarely seen or thought about, but one that we cannot live without. It must work 100% of the time for our homes to be habitable. This is the system by which our wastewater (typically called gray water and black water) leaves the house.
Sewer or septic: which does your home have?
Every Rhode Island home sends its wastewater to one of two places: a municipal sewer line, or an on-site septic system that the homeowner is responsible for.
Municipal sewer lines
Many Rhode Island homes are served by municipal sewer systems. These homes tie into a complex grid of pipes made of materials like PVC and cast iron, which carry all gray and black water away from the home and toward treatment plants. Municipalities typically charge sewer fees or assessments to help support the cost of maintaining the network and plants.
Individual septic systems
According to RIDEM, more than 35% of homes and businesses in Rhode Island are served by onsite wastewater treatment systems, commonly known as septic systems. These property owners are individually responsible for treating their own wastewater. Many of the communities where septic systems are found are lower-density, rural, or agricultural areas where it is not economically feasible to run municipal sewer lines.
Good to KnowSeptic systems are designed and rated based on the number of bedrooms in a home, not the number of bathrooms (RI OWTS rules, §6.22). Keep this in mind. It comes up again when we talk about home value.
For homeowners served by municipal sewer lines, the attention you need to give wastewater is limited to your individual service line from your home to the street. But if your home has a septic system, it is essential to know the answers to these four questions:
- What type of system do I have?
- How well is it functioning?
- What will it cost to maintain?
- How does it affect the value of my home?
What types of septic systems are there?
Rhode Island septic systems fall into three broad generations: cesspools, conventional (gravity-fed) systems, and advanced treatment systems.
The technical term for an individual septic system is “Onsite Wastewater Treatment System,” or “OWTS.” You may also see “ISDS,” short for “Individual Sewage Disposal System.” These terms cover a range of systems, from cesspools to conventional systems to advanced treatment systems. It is often easiest to think of them chronologically.
Cesspools (Septic 1.0)
The first in-ground septic systems were called cesspools. (Think outhouses before this newfangled technology!) These systems were simple pits dug into the ground, often beehive shaped and typically lined with bricks or rocks, into which all of the home's wastewater was piped. They were covered with a single top. There was no treatment of the wastewater entering these systems, which allowed contamination of nearby groundwater and soil.
In 2007, Rhode Island enacted the Rhode Island Cesspool Act, which requires that all cesspools in the state be removed from service over time. The timeline varies (RIDEM):
- Near water: Cesspools within 200 feet of tidal shorelines, public drinking water wells, or drinking water intakes had to be replaced by January 1, 2014.
- At sale: Under a 2015 amendment, most property sales and transfers trigger a requirement that an existing cesspool be removed from service within one year of the closing date. Certain transfers between family members or into family trusts are exempt. This has led to the slow but steady removal of cesspools as homes sell.
- At failure: A failed cesspool must be replaced within one year of the failure, or sooner if there is an imminent threat to public health.
The law does not specify whether the buyer or the seller pays for the cesspool upgrade, so it is subject to negotiation between them (RIDEM).
Conventional (gravity-fed) systems
The next generation of OWTS after cesspools is known as “conventional” septic systems. These are the most common type of OWTS in the US and are also known as “gravity-fed” systems (URI Onsite Wastewater Resource Center). In simple terms, they come in three parts:
- A septic tank
- A distribution box
- A drainfield (also called a leachfield)
Conventional systems rely on the surrounding soil for additional wastewater treatment and require suitable soil conditions and adequate separation from groundwater. They are best suited to lower-density areas with enough space to meet setbacks from property lines and storm drains.
Advanced treatment systems
The installation and maintenance of an OWTS is highly regulated by the Rhode Island Department of Environmental Management (RIDEM) in collaboration with each municipality. According to RIDEM's Septic System Checkup handbook, Rhode Island's septic systems discharge some seven billion gallons of wastewater into the ground each year. Now more than ever, the state and towns are paying close attention to water quality and how OWTS affect it.
As technology has advanced and our understanding of how wastewater affects groundwater has grown, several new types of OWTS have been developed for homes that cannot accommodate a conventional system due to factors such as:
- Poor soil quality
- A high water table
- A small lot
- Proximity to the shoreline
- Challenging setbacks
RIDEM's rules require a soil evaluation by a RIDEM-licensed Class IV soil evaluator for new construction and alteration applications, but not for residential repairs (§6.16). Site conditions and RIDEM's requirements determine what type of system can be installed. If an advanced treatment system is required, a RIDEM-licensed OWTS designer must design it. Advanced treatment systems differ from conventional systems in a few ways:
- They require an engineered, RIDEM-approved septic design plan.
- They further treat the wastewater before it is dispersed to the soil, reducing pathogens and nitrogen and decreasing the “strength” of the wastewater.
- They generally rely on pumps and timers and require annual or semi-annual maintenance to function properly (URI).
How well is my septic system functioning?
The only reliable way to know is an inspection by a trained septic inspector. In Rhode Island, a home-purchase septic inspection typically includes a visual inspection and a flow test.
Before purchasing your new home, we strongly recommend a septic inspection by an inspector listed on the URI Onsite Wastewater System Inspector Registry. Inspectors on the registry have completed URI training and passed an exam. The flow test (also called a hydraulic load test) recreates a scenario that pushes the system to its limits to see whether it can accommodate a large influx of water in a short time.
How the flow test works
- The amount of water pushed through the system is calculated by multiplying the number of bedrooms in the home by two (how many adults each bedroom is designed to accommodate), then running a set number of gallons of water per person through the system.
- As the water pours in, the inspector measures the level in the septic tank.
- If the level rises, the leachfield is not able to accept all of the wastewater coming through the system. This could mean the system is failing.
Already own a home with a septic system?
If you currently own a home with an OWTS but don't know much about it, it may be wise to have your system inspected now to understand how it is functioning. At a minimum, it is always a good idea to speak with a trusted septic inspector to understand the type of system you have and its current condition.
Pro TipYou can look up your home's septic records through RIDEM. Permits issued before April 17, 2025 are in the Historic OWTS Search, and newer permits are in RIDEM's Online Permit Search. You can also reach out to your town's wastewater manager.
What are the costs associated with septic systems?
Homes with septic systems don't pay municipal sewer fees, but they do carry ongoing pumping and inspection costs, and the largest expense comes if a new system needs to be installed.
Ongoing costs: pumping and inspection
Existing systems typically require two types of expenses, pumping and inspection, and requirements vary by municipality.
- Conventional systems require routine pumping and periodic inspection. RIDEM notes that most systems need pumping every two to five years, depending on system size and use. Many homeowners we work with choose a more frequent two- to three-year schedule. Your local septic pumping company can recommend a frequency and share pricing. Pump-outs typically cost $200 to $500 per visit, depending on the size of your tank.
- Tank size follows the number of bedrooms. Rhode Island's OWTS rules require a minimum 1,000-gallon tank for homes with up to three bedrooms, plus 250 gallons for each additional bedroom (1,250 gallons for four bedrooms, 1,500 for five).
- Inspection requirements vary by town, based on your system type and how much documentation the town has on it. We recommend checking with your municipality for your OWTS inspection requirements.
- Advanced treatment systems require routine pumping plus an Operation and Maintenance (O&M) Agreement with a service provider for semi-annual inspections. Pump-out pricing can be similar to a conventional system, but advanced treatment systems must have an O&M agreement in place at all times.
Installing a new system
The most significant costs of an OWTS come at the time of installation. In simplified terms, RIDEM categorizes applications as:
- Repair: repairing a system, or replacing a substandard system or cesspool, with no change of use and no increase in design flow.
- Alteration: generally, adding one bedroom to an existing home.
- New building construction: new construction, or adding two or more bedrooms.
Here are some of the expenses to consider when a home needs a new system:
- Soil evaluation by a RIDEM-licensed Class IV soil evaluator (when required)
- Engineering and design (required for advanced treatment systems)
- RIDEM administrative fees for approvals and site visits
- Installation: labor and materials
- Landscaping after completion
Recent Quotes We've SeenCosts vary by contractor, time of year, and site conditions. Recent quotes we've received for 3-bedroom systems (all of the above services combined):Conventional system: $32,000 to $38,000
Advanced treatment system: $38,000 to $48,000
How does a septic system affect the value of my home?
The single most important thing to know: your home's approved septic capacity is tied to its number of bedrooms.
This is why it is so important to understand your OWTS. Rhode Island regulations do not allow a residence served by an OWTS to have more bedrooms than permitted under the RIDEM-issued permit for its system (§6.22). That is an important detail to verify before listing or purchasing a home, particularly when the tax card and septic records don't agree.
From Katy's FilesI have clients who purchased a home with me this year. The house was listed as a 3-bedroom home. During my due diligence with my clients, I discovered that the home had been serviced by a 1-bedroom septic system for the last 44 years! We successfully negotiated a new septic system, and the listing agent learned a hard lesson about preparing for a sale. It was an expensive oversight that cost the sellers close to $40,000.— Katy Donovan, Broker/Owner
If you are one of the Rhode Island homeowners with an OWTS, it is essential that you understand your system: the type, the age, the condition, and the number of bedrooms it is designed to accommodate.
If you are a buyer considering a home in an area where OWTS are the norm, make sure you are working with a Realtor® who understands the nuts and bolts of this essential home system. The costs of owning a home with a septic system can be high, but the cost of not knowing what lies within your home's OWTS can be even higher.
What's different across the state line
Massachusetts handles septic at the time of sale differently. Under the state's Title 5 rules, a septic system must generally be inspected within two years before a sale, and an inspection remains valid for three years if the system has been pumped annually and the records are available. The property owner or operator is responsible for arranging the inspection, although the buyer and seller may agree in writing to change that responsibility (Mass.gov).
Unlike Massachusetts, Rhode Island does not have an equivalent statewide time-of-sale inspection requirement for conventional septic systems, although local requirements may apply (URI). Cesspools are subject to separate state requirements when a property is sold or transferred.
A few practical takeaways
- More than 35% of Rhode Island homes and businesses are served by onsite wastewater treatment systems.
- Residential septic capacity is tied to bedrooms, not bathrooms, and a residence cannot have more bedrooms than its RIDEM-issued OWTS permit allows.
- When most Rhode Island properties with a cesspool are sold or transferred, the cesspool must be removed from service within one year of closing.
- RIDEM says septic tanks typically need pumping every two to five years, depending on system size and use. Advanced treatment systems also require ongoing professional maintenance.
- Recent quotes we've received for a new 3-bedroom system ranged from $32,000 to $48,000, depending on the type of system and site conditions.
- RIDEM records can help homeowners and buyers determine what type and size of system has been approved for a property.
Frequently asked questions
How do I know if my Rhode Island home has septic or sewer?
Ask your town's sewer or wastewater department, or search RIDEM's OWTS permit records for your property. A septic inspector can also locate and identify your system.
How often does a septic tank need to be pumped?
RIDEM notes most systems need pumping every two to five years, depending on system size and use. Advanced treatment systems also require semi-annual inspections under an O&M agreement.
What happens to a cesspool when a Rhode Island home is sold?
Under the Rhode Island Cesspool Act, most sales and transfers require that the cesspool be removed from service within one year of the closing date. Certain transfers between family members or into family trusts are exempt. The law doesn't specify whether the buyer or the seller pays for the upgrade, so it's negotiable.
How much does a new septic system cost in Rhode Island?
Recent quotes we've received for a 3-bedroom home ranged from $32,000 to $38,000 for a conventional system and $38,000 to $48,000 for an advanced treatment system, including soil evaluation, engineering, fees, installation, and landscaping.
Can a Rhode Island home have more bedrooms than its septic system is permitted for?
No. Rhode Island regulations do not allow a residence served by an OWTS to have more bedrooms than its RIDEM-issued permit allows, even if the tax card lists more. It's worth checking before you list or buy.
A quick note: The information here is meant for general education and isn't a substitute for professional advice. Septic regulations, costs, and local requirements change and vary by town. Before buying, selling, or making changes to a system, consult RIDEM, your municipality, and a qualified septic professional.
This is the second post in our Know Your Home series. More to come!
Questions about septic systems, inspections, or anything else on your mind as a homeowner? Get in touch with our team. We're always happy to help. Contact us
