Norweco Septic System Review: Models, Maintenance, and Problems
The Norweco Singulair Green is an NSF/ANSI 245-certified aerobic treatment unit that uses a 3-chamber, 1,300–1,500 gallon design to reduce required drainfield size by up to 75%. It processes wastewater more thoroughly than a conventional septic system by injecting oxygen into the treatment tank. Aerobic bacteria break down waste faster and more than the anaerobic process in a standard tank. The trade-off: higher upfront cost, a mandatory annual service contract, and mechanical components that can and do fail.
We reviewed the types of septic systems available to homeowners, and Norweco comes up consistently for properties where a conventional system won’t work: small lots, sites near water bodies, or areas where local code requires advanced treatment.
Quick specs (singulair green vs BNR)
| Feature | Singulair Green | Singulair BNR |
|---|---|---|
| Tank size | 1,300–1,500 gallons | 1,300–1,500 gallons |
| Chambers | 3 (pre-treatment, aeration, clarifier) | 3 + denitrification |
| NSF certification | NSF/ANSI 245 | NSF/ANSI 245 + nutrient reduction |
| Power required | Yes (air compressor) | Yes (air compressor) |
| Drainfield reduction | Up to 75% | Up to 75% |
| Best for | Standard residential sites | Near lakes, coastal zones, nitrogen-sensitive watersheds |
The EPA classifies Norweco as an aerobic treatment unit (ATU). Per EPA guidelines on aerobic treatment units, ATUs inject oxygen to increase bacterial activity and nutrient treatment. They’re designed for small lots or homes near sensitive water bodies where conventional systems aren’t permitted or can’t achieve sufficient treatment quality.
How the Singulair Green works (the 3-chamber process)
Wastewater settles into the pre-treatment chamber, where heavy solids sink to the bottom. From there, it moves into the aeration chamber, where an electric air compressor, rated at 100 PSI, continuously injects oxygen, maintaining adequate mixing and diffusion for optimal aerobic bacterial growth. These bacteria form a robust population that breaks down organic material far more effectively than anaerobic bacteria in a conventional tank, achieving up to 95% efficiency.
Regularly check the compressor’s operation; it must start properly without tripping the breaker. Failure to do so could result in prime loss and compromised effluent quality.
After the aeration chamber, treated effluent moves to a clarifier chamber for final settling before dispersal to the drainfield. The 24-hour continuous treatment cycle means wastewater is always being processed, with no batch processing or idle period.
The result is effluent quality high enough that the required drainfield can be dramatically smaller than a conventional system demands. That’s the core reason Norweco gets specified for tight lots and sensitive sites.
Models compared: singulair green vs. singulair BNR
The Singulair Green is Norweco’s standard residential model and handles conventional treatment for most sites. It removes BOD (biological oxygen demand), TSS (total suspended solids), and pathogens to NSF/ANSI 245 standards.
The Singulair BNR (Biological Nutrient Reduction) adds a denitrification step that removes nitrogen before effluent reaches the drainfield. It’s required in jurisdictions with nitrogen-sensitive water bodies: parts of Florida, the Chesapeake Bay watershed, coastal Virginia and Maryland, and similar areas.
An older concrete-tank Model 960 still appears in some regional markets. But the plastic Singulair Green is the standard for new residential installations. If your contractor quotes a Model 960, ask why.
Check with your local health department before ordering any model, since some jurisdictions specify which Norweco configuration is code-compliant for your site.
Maintenance requirements
This is the part that gets undersold at installation. Norweco systems require real ongoing maintenance, and most of it isn’t optional.
Often overlooked.
Annual service contract is required as a permit condition in most states. For a complete task list, see our guide to aerobic septic system maintenance. A licensed Norweco service technician inspects the air compressor, float switches, chlorinator, and tank levels. Budget $150–$350 per year depending on region. This is the biggest ongoing cost difference from a conventional system.
Chlorine tablets or UV disinfection: Most states require disinfection before dispersal. If your system uses chlorine tablets, you add them to the chlorinator yourself every 3–6 months, roughly $20–$40 per year for tablets. Some systems use UV disinfection instead; that requires lamp replacement every 1–2 years.
Air compressor lifespan: The compressor motor typically lasts 5–10 years before needing replacement. Replacement cost runs $300–$600 installed. When the compressor fails, the system goes anaerobic, it’s operating like a conventional septic tank without the treatment quality your permit requires. Get it replaced promptly.
Pumping: Every 3–5 years, same as a conventional system. Per the EPA, standard pumping frequency is every 3–5 years depending on household size, tank size, and waste volume. Alternative systems with mechanical components like Norweco require annual inspections on top of the standard pumping schedule.
See our septic tank maintenance schedule for a full task checklist by month.
Common problems
Alarm activation is the most frequent homeowner complaint. The red alarm light means the system detected a problem: usually aeration failure, high water in the tank, or loss of power. Check the circuit breaker first. If power is fine, call your service technician. Don’t run the system in alarm state for extended periods.
Air compressor failure is the most costly problem. Symptoms are obvious: no air bubbling sound from the aeration chamber, followed by the alarm activating. Repair isn’t DIY-friendly. The compressor draws significant current and is integrated into the system controls. Licensed service only.
Chlorinator clogging is common and often ignored. Tablets don’t dissolve evenly, and the tube feeding them into the discharge can clog with scale or debris. If your service report shows inadequate residual chlorine, the chlorinator is the first place to look.
Odor at the drainfield signals that treatment quality has dropped, usually because the compressor is underperforming or the system is overloaded. Don’t mask it; address the root cause.
Unexpected service costs: Annual contracts don’t always cover parts. Ask your service provider specifically what the contract includes and what triggers a billable service call. We recommend getting that scope in writing before signing the contract.
Is it worth it?
Norweco makes sense when your lot is too small for a conventional drainfield, when your site is near a water body requiring advanced treatment under local code, or when your jurisdiction requires NSF-certified ATU performance.
It’s likely overkill when your property can support a conventional system. The lower upfront cost and no annual service contract makes conventional a better financial fit. If your jurisdiction accepts passive biofilter systems like EcoFlo, those achieve advanced treatment without electricity or service contracts.
Common mistake.
If your property requires an ATU, Norweco’s NSF certification and 24-hour treatment cycle make it a solid choice. If a conventional or passive system is code-compliant for your site, the $150–$350 annual service contract is hard to justify.
Nothing fancy.
Check the Norweco residential products page for current model specs, and verify NSF certification for your specific unit at NSF septic system certification standards.
You may also want to compare the EcoFlo biofilter alternative, a passive system that achieves comparable treatment without electricity.
For pumping schedules and what to expect from ongoing maintenance, see how often to pump your septic tank.
FAQ
How much does a Norweco septic system cost?
Installed systems vary widely by location and site specifics; allocate between $10,000 and $15,000 for installation. Add permit fees in the range of $500 to $1,500 and a soil evaluation costing from $300 to $500. For annual upkeep, factor in a service contract fee of around $150 to $350 yearly. Over ten years, the total ownership cost including pumping expenses is likely to hit between $13,500 and $19,000.
How long does a Norweco Singulair Green last?
The tank itself is designed to last 20–30 years. The air compressor motor typically lasts 5–10 years before replacement ($300–$600 installed). With annual inspections and timely compressor replacement, the system can run for several decades.
What happens when a Norweco alarm goes off?
The red alarm light signals that the system detected an issue: most commonly aeration failure, high water level in the tank, or loss of power to the compressor. Check the circuit breaker first. If power is normal, call your service technician. Don’t ignore a sustained alarm. The system will revert to anaerobic treatment and won’t meet its permit requirements.
Does a Norweco system need to be pumped?
Yes. Norweco systems require pumping every 3–5 years, the same as a conventional septic system. The aerobic treatment process reduces solids more than a conventional system, but solids still accumulate and require periodic removal.
Is the Singulair Green the same as an ATU?
Yes. The Singulair Green is Norweco’s brand name for their aerobic treatment unit (ATU). ATU is the generic EPA classification for any system that uses aerobic bacteria (requiring oxygen) rather than the anaerobic process in a standard septic tank. All Singulair Green systems are ATUs, but other manufacturers make ATUs as well.