Septic FAQ

Frequently Asked Questions

Questions Regarding the Application Process

Please refer to the Road Map Page and this fact-sheet regarding the S.E.P.T.I.C Grant Program Application Process.  If you have any questions not addressed in the fact-sheet or on the Grant Road Map, please email

Questions Regarding Clean Water (nitrogen-reducing) Septic Systems

How do the approved technologies reduce nitrogen? 

The approved nitrogen-reducing technologies (also known as Innovative and Alternative Onsite Waste Treatment Systems or I/A OWTS) use filtration and biological processes to ultimately convert the organic nitrogen found in wastewater into harmless nitrogen gas.  This is commonly achieved by separate compartments in the septic tank  The first compartment is typically anoxic, meaning there is no oxygen present in the wastewater.  This compartment also contains human waste which is a good source of carbon to feed the “good” bacteria that denitrify, or convert nitrate nitrogen to harmless nitrogen gas.  The second compartment usually introduces oxygen through filters, blowers, or aerators to convert the ammonium in wastewater to nitrate nitrogen.   This effluent is now much cleaner but it needs to be sent to a carbon rich anaerobic environment  for denitrification, which occurs when aerobic bacteria, now starved in an oxygen depleted environment,  strip the oxygen molecule off of nitrate nitrogen, resulting in the release of gaseous nitrogen harmlessly into the atmosphere. The nitrogen cycle is one of Earth’s most important biological processes, second only to photosynthesis.

How does a Clean Water Septic System (IA/OWTS) benefit the property owner?

In addition to providing environmental benefits and reducing the nitrogen load to ground and surface waters, property owners receive many other benefits from these state-of-the-art technologies. I/A OWTS can be more cost effective than conventional systems on lots with significant site constraints such as high groundwater, poor soils, small restrictive lot size, and coastal areas. In addition, I/A OWTS consist of separate components, all of which are replaceable if something goes wrong. A property owner may have to replace a pump or blower after 10 years, but should not have to dig up and replace the system as is common with conventional systems. 

How does a Clean Water Septic System (IA/OWTS) benefit the environment?

Conventional septic systems and cesspools are not designed to remove nitrogen.  As a result, nitrogen in sewage easily seeps into the ground, then to groundwater, and ultimately to our bays and harbors where they can lead to excess nitrogen.  Too much nitrogen can lead to algae blooms (some of which are toxic to humans) and when these blooms die off, the deplete the bay of oxygen needed for fish and other marine life. In addition, excess nitrogen can lead to loss of wetland marshes as their roots become too shallow to withstand storms and other disturbance. Since these wetlands protect the shorelines from storms and also serve as a natural filter for stormwater from the land and also provide habitat for marine life, their destruction can cause significant impacts. These IA/OWTS systems have been shown to remove up to 90% of the nitrogen that leads to these problems.

Which pollutants, other than nitrogen, does the system treat for, if any?

I/A OWTS are designed to reduce wastewater nitrogen, biochemical oxygen demand (BOD), and total suspended solids before being discharged below grade to leaching structures.  Please consult with the manufacturer (or authorized installer) of your I/A system to learn more about the capabilities of their technology. Although studies have shown that certain I/A systems may reduce other pollutants, the purpose of this program is to address and reduce the prevalence of nitrogen in our waterways.

What are the electrical demands? 

I/A OWTS electrical consumption vary from system to system due to different treatment processes with different pumps and blowers required to treat the wastewater. Of the systems that have been provisionally approved, annual electric costs are currently estimated to range from $57 to $266 per year. Please consult with the manufacturer (or authorized installer) regarding your I/A system’s power needs. It is important that you ask if pumps will need to be installed with your project (typical with basement bathrooms and areas with high groundwater) and what backup power solutions are necessary in the event of power loss to your home.

What kind of maintenance is required for these systems?

These systems require inspection and maintenance at least once per year, though most technologies are maintained every 6 months.  The  maintenance typically includes cleaning of filters, pumps, and floats, measuring oxygen levels, and ensuring  the system controls are optimized for nitrogen removal.  The Service Provider will also monitor the solids in the tank and recommend pumping as needed. As part of the grant, a three-year maintenance agreement is included with the installation contract. Maintenance agreements are required for the life of the system and proof must be shown to the County or its designated agent each year. Reminders will be automatically emailed to grant recipients each year. Typically, maintenance agreements cost about $300 per year. Proper maintenance helps ensure that these systems continue to remove nitrogen as designed (the purpose of the grants). Failure to provide the County with proof of a maintenance contract may result in the obligation to repay the amount of the grant.

Will my system be tested from time to time?

Systems that have been designated as provisionally-approved are required to be tested monthly for at least one year. At present (August 2021), all systems being installed fall into this category.  As a result, a representative of the manufacturer may be coming to sample your system. They will not need to enter your home. They will obtain a sample through one of the access pipes on the system. 

Questions Regarding S.E.P.T.I.C. Grant Program

We want to upgrade to reduce our nitrogen output, our system is ancient but not failing (yet), are we eligible for a S.E.P.T.I.C. Grant to install an IA OWTS?

The New York State Department of Environmental Conservation has determined that conventional septic systems and cesspools on Long Island are considered failing since they are neither designed, nor capable of removing significant amounts of nitrogen. “Failure” – also means evidence of dye on the ground surface or in a watercourse, evidence of sewage effluent on the ground surface or in a watercourse, or other obvious failure of system components (i.e. collapse of a septic tank). Observed effluent may need to be confirmed as a “failure” by the introduction of dye into the treatment system and subsequent field observation for dye. 

If we meet all the eligibility requirements is there any other reason why the grant would not be given?

Yes, as of 2021, there are currently enough County and State funds for 200 grants. Provisional grant acceptance is given on a first-come, first-served basis to qualified applicants.  If demand for the Program exceeds available funding, the District reserves the right to modify program rules to set more restrictive criteria to prioritize the most environmentally sensitive areas.

If I have an I/A-OWTS installed with a grant from the S.E.P.T.I.C. Program, can I remove the unit or make it inoperable? 

No, the conditions of funding do not allow for removal or deactivation. Be sure you are committed to this system and its maintenance requirements before applying for a grant. 

Must a recipient maintain service in perpetuity? 

Yes, the recipient is responsible for ensuring that their grant-funded system is inspected and maintained at least once per year by a licensed service provider. 

Does the process require any approvals? 

Design professionals (engineer or architect) should help residents understand which permits would be required for electric, plumbing, wetlands, or dewatering. It is recommended that a property owner’s selected design professional check with the local town/village building department to verify if a permit is required for the I/A OWTS electrical work or for any internal plumbing modifications if required in addition to a building permit. For residents in close proximity to surface waters and/or wetlands, their selected design professional should check with the NYS DEC and/or Town/Village to determine if a permit is required due to setbacks to surface waters or wetlands. 

Is the program tax deductible? 


Are the materials exempt from sales tax because the project is considered a capital improvement?

Applicants must consult their tax professional regarding any tax exemptions, requirements, or other tax implications that may exist.  Please note that the County / District do not provide tax advice to Applicants.  Applicants must submit  NYS  form ST-124 if claiming any capital improvement sales tax exemptions in accordance with NYS Requirements.

Are the grant funds taxable?

At present (August 2021) the IRS considers the grant amount taxable to the property owner even if the funds are paid directly to the installer and/or designer. Efforts are underway in Congress to remove these types of grants from taxation. For the latest information, please contact the Nassau County Soil and Water District office at (516) 364-5861.

Design considerations 

A comprehensive soil and site investigation will identify the preferred location and the type of system that is appropriate for the site conditions. Separation distances between IA/OWTS components and property boundaries, structures (existing or planned) and other site features are necessary. The required infiltrative area is determined from: (a) properly conducted soil percolation and deep hole tests to accurately identify the site and soil conditions and (b) projected wastewater dispersion direction.

How do I measure the treatment capabilities of my current system and confirm whether or not it is less than 1,000 gallons per day?

An IA/OWTS serving up to a 9-bedroom single-family residence are generally eligible for S.E.P.T.I.C. Grant assistance.  For small businesses, a good guide to measure if your building discharges less than 1,000 gpd is to look at your water bill and usage.  For specific design and system sizing requirements please refer to NYS Department of Health Appendix 75-A Wastewater Treatment Standards – Residential Onsite.

I rent out a house on my property, would this building’s system be eligible for an I/A upgrade through the SEPTIC program?

Yes, assuming the total design discharge is less than 1,000 gallons per day.

I have more than one building on my property utilizing the same system, would I be eligible for an I/A OWTS upgrade?

Yes, assuming the total design flow is less than 1,000 gallons per day.

Does the S.E.P.T.I.C. grant program reimburse sales tax?

No, sales tax is an ineligible cost and will not be reimbursed.

What are the FEMA flood zone construction requirements?

Your Design professional can provide you with the regulatory and manufacturer requirements for your FEMA Designated Flood Zone.

If grant funds cannot be used for new construction, what about substantial reconstruction?

Grant funds can be used for repairs to an existing system using I/A OWTS technology.  Therefore, if the property is undergoing reconstruction, but has a previous system in place prior to March 1, 2018, it would be eligible under the program.

I am building a new house and wish to install an I/A OWTS system. Would I be eligible for the program?

While new construction is not eligible for the program, if there is a current system in place for the property (i.e. the old house was demolished in order to build a new one) that has existed since before March 1, 2018, the property would be eligible for an upgrade to an I/A OWTS system under the program.

Can I apply for the S.E.P.T.I.C. Grant Program retroactively? 

Yes, you may apply retroactively to the installation of an I/A OWTS system as long as the system was installed after March 1, 2018.  However, applying does not guarantee that you will receive a grant award.  

What costs are eligible for reimbursement through this program?

To be eligible for reimbursement, an incurred cost must be reasonable and necessary for work done to a septic system if it is determined by the County or its authorized agent.  Eligible costs are listed below:

  • Design and installation costs, and costs of the system, system components, or enhanced treatment technologies. Note that grant funds must first be used to pay for installation costs and if funds remain after this, they can be used to reimburse the property owner for some or all design costs.
  • Design costs are eligible (subject to the above), limited only to work needed to complete an approved design, including needed site investigation. Note that design costs will only be reimbursed if funds remain after covering installation costs. 

What costs are ineligible for reimbursement through this program?

  • Routine maintenance such as a pump out of a septic tank. 
  • Any expenses that are not appropriately documented
  • Government permit fees, including but not limited to fees assessed for building permits, zoning permits, and floodplain disturbance permits
  • Interest and late fees
  • Fines and penalties 
  • The payment of sales tax
  • Non-essential site beautification such as landscaping or interior plumbing changes
  • Administrative work conducted by the engineer
  • Construction observation by the engineer if the engineer, or an entity owned, controlled by, or employing the engineer, is also conducting the repair or replacement.
  • Abandonment and decommissioning of an existing septic system
  • Cost for obtaining an electrical underwriting certificate (if required by the permitting agency)

We presently have two cesspools for a single-family home - one for solid waste and an overflow for wastewater. Would we qualify for the program?

Yes, as long as the sanitary flow design into the system is less than 1,000 gallons per day.

Are properties owned by not-for-profit organizations eligible for the grants

Yes, they are eligible, provided that the design  discharge is less than 1,000 gallons per day.

Are employees of Nassau County, New York State, or the federal government eligible to apply?

Yes, they are eligible. 

If my property is in an area with sewer service or proposed for sewer service, am I eligible to apply?

No, you will be required (if not already) to connect to the sewer system.

How do I find contractors to design and install my system?

First, you need to know that you need both a Designer (engineer or architect) to design your system and an Installer to install your system. New York State law does not allow the same firm to both design and install systems. The County and the Nassau County Soil and Water Conservation District solicit proposals from designers and installers whereby they provide their qualifications and their prices. Once approved, this information is posted on the S.E.P.T.I.C. Program website ( These lists are expected to be posted in October 2021 and periodically updated. In the interim, you may consult the Designer or Installer lists that have been published by The Suffolk County Department of Health Services. Note that installers must have a Nassau County Home Improvement License issued by the Nassau County Department of Consumer Affairs.