Septic in Milton, NH

Last updated: Mar 21, 2026

Milton's open lots, pine-needle litter, and quiet cul-de-sacs often mean more space between homes and the sewer lines, which is why septic systems are a familiar neighbor here. If you're buying or owning a Milton home, you'll likely encounter a septic system unless you're on a town sewer. This guide is here to help you understand what to expect and how to keep your system healthy.

Is septic common in Milton? Should I expect septic if I own or buy a home?

In Milton, most homes rely on on-site septic systems because centralized sewer service isn't available to every street or subdivision yet. If your property isn't connected to a municipal sewer main, you should expect a septic system.
If you're buying a home, ask for: the as-built septic plan, last pump date, inspection reports, and any maintenance notes. Confirm whether the home is on a conventional septic or an alternative system (mound, advanced treatment, etc.). Check the distance to wells and any setbacks required by local or state rules.

Why homes typically use septic systems in Milton

Rural layout and lot sizes: Milton has many private wells and individually owned lots that make on-site wastewater treatment practical and economical.
Limited sewer infrastructure: The town's sewer network isn't universal, so on-site treatment remains the norm for many neighborhoods.
Groundwater and environmental considerations: Properly designed septic systems help protect drinking water and local streams when soils and groundwater conditions are favorable.

High-level explanation (why septic exists here)

A septic system is a compact wastewater treatment solution that works best when placed in suitable soils. In Milton, typical homes rely on a septic tank to separate solids from liquids, with a leach field or trench soil area where treated effluent slowly infiltrates. This on-site approach minimizes surface disruption, supports private wells, and aligns with the rural character of the town.
Some properties with challenging soils may use enhanced or alternative systems, such as mound systems or newer treatment technologies, to achieve proper wastewater treatment while protecting groundwater.
Regular maintenance is the key: routine pumping, inspections, and avoiding overloading the system with fats, chemicals, and non-degradables keeps the system functioning for decades.

A friendly, practical note from your local neighbor and septic pro

Common-sense upkeep goes a long way: keep heavy loads off the leach field, plant trees away from the drain area, and budget for a pump every 3–5 years (or as advised by the system designer).
If you're unsure about your Milton septic, I'm here to help you interpret disclosures, estimate maintenance needs, and map out a simple care plan that fits your family's usage.

If you're navigating a Milton home's septic questions, you've got a neighbor in your corner who's also a local pro—ready to help you keep things flowing smoothly.

Where Septic Systems Are Common in Milton

Rural, Large-Lot Living

Milton's landscape and zoning mean many homes sit on substantial parcels. On these large lots, septic systems are the practical and common method for handling household wastewater. Typical lot sizes—often one acre or more—give space for septic fields that keep effluent away from wells and property lines, reducing conflicts over drainage and water use.

You'll often see conventional gravity septic setups on these properties.
Space and soil variability across a rural town encourage a mix of system types to fit the site.

Limited Public Sewer Coverage

Public sewer lines are not universally available across Milton. They tend to exist in the village centers or along major routes where town investment has extended wastewater collection. Outside those areas, homeowners rely on on-site wastewater treatment.

If you live near a village core or along an established sewer corridor, your home may be connected or have a sewer lateral near your property.
In outlying neighborhoods, septic systems remain the standard, with design and maintenance tailored to individual lots.

Village Centers, Developments, and Zoning

Where new subdivisions have been built, you'll still see septic systems for most homes unless a sewer district was created and connected. Zoning in Milton often preserves rural character, maintaining lower densities that support on-site systems rather than municipal treatment for every lot.

Older homes in historic pockets typically use individual septic tanks with leach fields.
Newer developments may use modern septic designs or, in some cases, cluster septic layouts designed to protect water resources.

Soil, Groundwater, and Siting Considerations

Soil type and groundwater depth drive septic performance more than anything else. Milton sits on a mix of soils, from well-drained sands to clays and shallow bedrock in low-lying areas. The local hydrogeology influences where a system is placed, how large it must be, and what maintenance it will require.

Well-drained soils support efficient septic disposal fields, while poorly drained soils may require specialty designs.
Shallow groundwater or proximity to wells calls for careful setback planning and possibly alternative systems.
Use official soil maps to get a sense of what your site poses for a septic system. The USDA Web Soil Survey is a reliable starting point:
U.S. Environmental Protection Agency (EPA) – Septic Systems: https://www.epa.gov/septic
USDA NRCS Web Soil Survey (soil data to assess your site): https://websoilsurvey.nrcs.usda.gov/

Septic vs Sewer: What Homeowners in Milton Should Know

Milton homeowners face two main options for handling household wastewater: septic systems on private property or municipal sewer service. Understanding how each works helps you plan for maintenance, budget, and compliance with local and state rules.

How a septic system works

Wastewater from toilets, sinks, and appliances flows into a septic tank where solids settle and scum floats. Liquid effluent then moves to the drainfield for treatment by soil and microbes. Regular pumping of the septic tank removes accumulated solids and prevents backups. Key factors that affect performance include tank size, household water use, soil type, and drainage design.

Septic tank: collects and separates solids from liquids.
Drainfield: perforated pipes buried in unsaturated soil where effluent is treated before reaching groundwater.
Soil: natural filtration and microbial activity that reduce contaminants.
Maintenance: scheduling pumping, avoiding harmful chemicals, and monitoring for signs of failure.

What sewer service means for Milton residents

If your property is connected to a municipal sewer, wastewater travels through public mains to a centralized treatment plant. The town or regional district handles maintenance, and you typically receive a regular utility bill for sewer service, separate from water.

Public responsibility: central system, pumping stations, and treatment.
Billing: monthly or quarterly sewer charges.
System limits: capacity constraints and permit requirements may affect new connections or expansions.

Key differences at a glance

Ownership and responsibility: private septic vs public sewer.
Ongoing costs: septic requires pumping and occasional repairs; sewer is a recurring fee.
Land requirements: septic needs suitable soil and space; sewer requires service availability.
Environmental considerations: both require proper use to protect groundwater and surface water.

Steps to decide which option fits your property

Verify service status with the Town of Milton (is your property sewer-connected or on septic?).
If septic, confirm tank size, last pump date, and household occupancy to estimate maintenance costs.
Compare anticipated annual septic maintenance against anticipated sewer bills.
Evaluate site conditions: soil suitability, groundwater depth, and lot drainage.
Plan for long-term needs: additions, high-water-use appliances, or future expansion.

Maintenance and regulatory considerations

Pumping frequency: most homes with a conventional septic tank need pumping every 3–5 years; urban use, tank size, and family size influence the interval.
Inspections: schedule inspections when purchasing a home or if you notice unusual drains, odors, or backups.
Chemical use: avoid dumping oils, solvents, or large quantities of cleaners that can disrupt beneficial bacteria.
Regulations: protect groundwater and comply with local and state rules; see official guidance below.

Resources and official guidance

EPA: Septic Systems Overview and Homeowner Tips —
For Milton-specific sewer service information, contact the Town of Milton's Public Works or Planning Department.

Typical Septic System Types in Milton

Conventional gravity septic systems

Most Milton homes rely on a conventional gravity system: a septic tank buried on site, with effluent distributing by gravity to a drainfield or leach field in the soil. The basic sequence is solids and scum settle in the tank, clarified liquid exits to perforated pipes, and wastewater slowly disperses through the soil.

How it works
- Wastewater enters the septic tank, solids settle, liquids flow to the drainfield.
- The drainfield uses gravity to distribute effluent through perforated pipes in a trench or bed within the soil.
Pros
- Simpler design and often lower upfront cost.
- Easy to service with routine pumping and field inspections.
Cons
- Requires adequate soil depth and permeability; performance drops with poor soils or high water tables.
- Drainfield failure affects entire system; repairs can be expensive.
When it's a good fit
- Typical lots with good soil structure and sufficient absorption area.
Maintenance notes
- Regular pumping (on the order of every few years, depending on usage and tank size).
- Protect the drainfield from compaction, heavy equipment, and drainage into the system.
- Watch for surface damp spots or lush vegetation over the drainfield—these can signal issues.

Alternative systems used in Milton

Low-Pressure Dose (LPD) or pressure-dosed systems

In soils with variable absorption or steeper lots, Milton homeowners may see pressure-dosed layouts. A pump distributes effluent to a network of laterals to improve even infiltration.

How it works
- A pump periodically distributes small amounts of effluent to several drainage lines.
Pros
- More uniform effluent distribution; can handle marginal soils better than gravity alone.
Cons
- Requires electricity and routine maintenance of the pump and control components.
When it's a good fit
- Sloped sites, shallow soils, or sections where gravity cannot reach all areas of the drainfield.

Mound systems

Raised "mounds" are used where native soil depth is limited, or groundwater is near the surface. Sand fill and a separate infiltrative bed sit above the natural soil.

How it works
- Wastewater goes to a tank and is dosed into an above-ground sand/soil system via a network of risers and drains.
Pros
- Allows reliable treatment when soil conditions are poor or perched water tables exist.
Cons
- Higher initial cost; more complex maintenance and system monitoring.
When it's a good fit
- Shallow soil, high water table, or bedrock close to the surface.

Chamber systems and advanced treatment units (ATUs)

Chamber systems use modular plastic chambers instead of traditional gravel trenches, while ATUs provide higher level treatment before the drainfield.

How it works
- Chamber systems use interconnected plastic modules to form the drain area; ATUs add aeration or polishing stages for cleaner effluent.
Pros
- Often easier to install with less heavy material; can withstand challenging soils.
- ATUs offer improved effluent quality in restrictive soils.
Cons
- May have higher maintenance costs and electricity needs (for ATUs and pumps).
When it's a good fit
- Lots with limited space, soils that don't support conventional trenches, or homes requiring enhanced treatment.

Quick Milton-specific considerations

Soil and site evaluation are essential. Milton's varied soils mean some lots require alternative designs (mound, chamber, or ATU) to meet absorption and setback requirements.
Local and state guidance matters. Always work with a licensed septic designer or contractor familiar with NH DES guidelines and Milton's regulations.
Maintenance matters more than you might think. Regular inspections, timely pumping, and keeping vehicles off the drainfield help extend system life.
Official resources
- NH Department of Environmental Services – On-Site Wastewater Treatment Systems (OWTS):
- EPA Septic Systems: https://www.epa.gov/septic

Common Septic Issues in Milton

Drainfield saturation from groundwater and heavy spring rains

Milton experiences seasonal spikes in groundwater and frequent spring precipitation, which can saturate the drainfield. When the soil is waterlogged, effluent has nowhere to go, leading to surface seepage, soggy patches, or backups inside the home.
Symptoms to watch for: slow drains, toilets gurgling, ponding on the leach field, or a strong sewage odor near the drainfield.

Steps to address:

Reduce water use during wet periods (short showers, run full loads in laundry).
Avoid driving or placing heavy objects on the drainfield.
If pooling persists, contact a licensed septic pro for an inspection and potentially a reserve or alternative drainage plan.

Soil conditions and site constraints unique to Milton

Milton's soils are a mix of glacial outwash sands, gravels, and pockets of clay, with zones of perched groundwater near wetlands or streams. This variability can make a drainfield perform unpredictably and may necessitate design adjustments or regular maintenance beyond typical homes.
Clay pockets slow percolation and can cause standing effluent, while sandy or gravely zones drain too quickly, reducing treatment time.

What this means for homeowners:

A one-size-fits-all maintenance approach rarely works. Local soil tests and a professional evaluation help determine appropriate pump schedules and leach-field sizing.
If you're buying an older Milton home, factor in potential upgrades (new distribution box, deeper replacement trenches, or soil-based remediation) into the budget.

Tree roots and physical intrusion

Many Milton yards have mature trees whose roots seek moisture and can infiltrate septic tanks, pipes, and leach fields. Root intrusion can crack pipes, block lines, and reduce drainage efficiency.
Signs include banging noises in the pipes, frequent backups after planting near the system, or roots visibly intruding from cleanouts.

What to do:

Schedule an inspection if you suspect root intrusion. A professional can locate lines, cut back roots, or install root barriers.
Keep trees away from the leach field and tank access spots whenever feasible.

Maintenance gaps: pumping, filters, baffles, and aging components

Poor maintenance is a common Milton-related issue. Inadequate pumping, neglected effluent filters, or failing baffles can lead to solids backing up into the drainfield, reducing treatment and shortening system life.
If your system is older, components like the outlet baffle or effluent filter may be degraded and require replacement.

Recommended maintenance:

Pump every 2-3 years for typical households; more frequently if you have a high-use sewer, a garbage disposal, or a household chemical burden.
Have a licensed pro clean or replace filters and inspect the tank, baffles, and distribution box.

Water management, disposals, and household chemistry

Sump pumps discharging into the septic system, excessive use of garbage disposals, and flushing wipes or certain chemicals can overload the treatment process and harm beneficial bacteria.
In Milton, where some homes have separate basements or crawlspaces connected to drainage, improper water routing can flood the system or introduce contaminants quickly.

What to minimize:

Don't discharge graywater from sinks or laundry into the septic system if alternatives exist (e.g., graywater reuse where permitted).
Use septic-safe products and avoid caustic cleaners, solvents, or large volumes of antibiotics unless prescribed.

Seasonal use, frost, and cold-weather effects

Milton's cold winters can slow bacterial activity and freeze vulnerable components if the system sits idle or the frost line is shallow.
Frozen or buried components increase the chance of backups when spring warms the ground and active systems ramp up again.

Mitigation tips:

Keep above-ground components accessible and clear of snow in winter.
If the home is seasonal, coordinate seasonal shut-down and start-up with a septic pro to avoid shock loads or prolonged inactivity.

What to do if you suspect a problem (milton-specific quick-start)

Minimize water use and avoid flushing non-flushable items.
Visually inspect for surface seepage, hydro-logged areas, or strong odors near the drainfield.
Schedule a licensed septic inspection or pumping as soon as possible.
Have soil and system integrity evaluated, especially if you notice wet areas after rain or the ground is unusually saturated.

Resources

EPA Septic Systems: (search for on-site wastewater)

Septic Inspection, Permits & Local Oversight

Who oversees septic work in Milton

In Milton, most onsite wastewater work is handled at the local level by the town's Code Enforcement Officer or Building Department, which issues permits and conducts inspections. State-wide standards are set and enforced by the New Hampshire Department of Environmental Services (DES). DES also licenses designers and installers who prepare plans and perform work to meet state requirements. If your project touches state rules or involves a failed system, DES involvement may be required in addition to the local permit.

When a permit is needed

New septic systems: local permitting is typically required, with a plan prepared by a licensed designer.
Replacements or substantial modifications: a permit is usually required if you are replacing or altering the disposal field, tank size, setbacks, or design.
Repairs that don't change the system's footprint or performance may still require a permit in some cases; check with the local Building/Code Enforcement Office.
Decommissioning or abandonment of an old system: permit and proper documentation are usually required.

Note: Local rules vary by town, so confirm Milton's specific requirements with the Building Department or Code Enforcement Officer.

The inspection and approval timeline (step-by-step)

Hire a licensed Onsite Wastewater System Designer to assess your site and prepare a compliant plan.
A thorough site evaluation helps ensure the design fits soil, slope, and lot constraints.
Submit the plan to Milton's local approving authority for review and a permit.
Include the site evaluation, proposed layout, setbacks, and any required fees.
Obtain the local permit before you start any work.
Keep the permit number visible on site and follow any stated conditions.
Hire a licensed installer to install the system per the approved plan.
The installer should be aware of inspection milestones and required documentation.
Schedule inspections at key milestones.
Typical milestones include after trenching/backfilling and after final installation.
The local authority will require compliance with the approved design.
After installation, file an as-built with the local authority (and DES if needed) and obtain final approval.
An as-built shows actual locations of tanks and drainlines and confirms the system is in regulatory compliance.

What to have ready when you apply

Address and lot details, size and slope, and setbacks to well, water body, or property lines.
Existing septic information (if any), including previous permits or issues.
Proposed wastewater flow estimates and household or business use.
Site constraints notes (rock, poor soil, seasonal high groundwater) and a rough drainage plan.
Names and licenses of the designer and installer you plan to use.

Helpful tips to avoid delays

Don't start work before you have a permit and an approved plan.
Ensure your designer and installer are properly licensed in New Hampshire.
Schedule inspections promptly and notify the local office as soon as milestones are met.
Keep copies of all permits, plans, inspection reports, and as-built drawings.

Common questions

Do I need a state permit in addition to a local permit? In many cases, the local permit is the primary requirement, but DES oversight applies for certain designs, failures, or state-regulated aspects of onsite systems. Check with Milton's Building Department and DES if you're unsure.
What is an as-built? A final drawing showing the actual locations of tanks, leach fields, and piping after installation, submitted to the local authority (and DES if required).

Official resources

New Hampshire DES Onsite Wastewater Program:
New Hampshire RSA 485-A (Onsite Wastewater Systems):
Milton town resources (Building Department/Code Enforcement contact): check Milton's official town site for the current contact page and fee schedule.

Septic Maintenance for Homes in Milton

Seasonal Timing and Pumping

Milton's cold winters and spring thaws create seasonal stress on septic systems. A regular pumping schedule helps prevent solids from reaching the drain field when groundwater is high.

Typical interval: a 1,000-gallon tank serving a family of four is commonly pumped every 2-3 years. Larger households or heavy disposal use may shorten that to 1-2 years. Keep a simple log.
How to know it's time: solids accumulate enough that the tank is half full of sludge and scum, you notice slowed drainage, backups, or sewage odors outside or in plumbing fixtures.
Best time to pump: late spring or early fall when the ground is unfrozen and the leach field is not saturated. Avoid mid-winter pumping when access and soil conditions are challenging.
After pumping, obtain a written service report noting sludge/scum depths and overall tank condition.

Steps to set your pumping schedule:

Confirm your tank size and current occupancy.
Review past pumping date(s) and any changes in usage (more people, new appliances, garbage disposal).
Schedule pumping with a licensed contractor and keep the service report for your records.

Milton-Specific Soil and Water Considerations

Milton features a variety of soils, with some areas closer to the water table. Seasonal groundwater fluctuations and frost can influence drain-field performance and recovery time.

Avoid driving or parking on the drain field, especially during spring thaw and after heavy rains.
Manage surface water: make sure roof drains and sump pump discharge are directed away from the leach field; proper grading helps prevent saturation.
Root protection: keep trees and large shrubs away from the drain field; plant only shallow-rooted grasses over the area.
Chemical exposure: minimize use of harsh cleaners, solvents, and motor oil near the system; avoid salt-based de-icers entering the septic system.
Well setbacks: Milton properties should follow New Hampshire DES setback guidelines for wells and surface features; check your property plan or official guidelines.

Routine Maintenance Checklist

A proactive routine protects Milton systems from springtime surges and winter freezes.

Water use and fixtures: fix leaks promptly; install high-efficiency toilets, faucets, and appliances; avoid overloading the system with laundry in a short period.
Garbage disposals: use sparingly; they add solids and grease to the tank.
Disposal habits: dispose fats, oils, and grease in the trash; avoid flushing medications, wipes, litter, or diapers.
Drains and cleaners: use septic-safe products; avoid chemical drain cleaners or products that claim to "boost" bacteria.
Drain-field protection: keep HVAC condensate, sump pumps, and outdoor drains from discharging onto the field; avoid parking vehicles or heavy machinery over the area.
Inspections: have a licensed septic professional inspect annually; they should measure sludge and scum depths and inspect baffles and pumps if present.
Record keeping: maintain pumping receipts and inspection reports in a Milton property file.

Signs of Trouble and Immediate Action

Watch for gurgling, backups, sewage odors indoors or outdoors, or wet, swampy areas above the drain field.
If you notice issues, limit water use and contact a licensed septic contractor promptly. Do not attempt DIY repairs beyond basic maintenance.

Professional Service and Record Keeping

Use a Milton-area licensed contractor for pumping, inspection, and any needed repairs.
After service, request a detailed report with sludge/scum depths, tank condition, pump status, and any recommended maintenance.
Keep all records for future sales or inspections and for local permitting considerations.

Official Resources

U.S. Environmental Protection Agency: Septic Systems
NH DES home page for onsite wastewater resources:

Cost Expectations for Septic Services in Milton

Septic Tank Pumping

What the service includes: removing accumulated sludge and scum from the tank, inspecting the tank interior and baffles, checking inlet and outlet pipes, and noting any signs of standing water or leaks. In Milton, many tanks are exhumed from earth and may have limited access; technicians often need to use portable pumps and extendable hoses to reach the tank. Regular pumping is the most cost-effective way to prevent solids from reaching the drainfield.
Milton-specific details: driveway access, snow cover in winter, and older tank configurations can influence access and timing. If the tank hasn't been pumped for a long period, expect a larger volume and a longer service time.
Typical cost in Milton: about $250–$450 per pumping.
Resource: Learn about onsite wastewater basics and pumping best practices from the U.S. EPA and NH DES:

Septic System Inspection (Routine or Real Estate)

What the service includes: visual inspection of the tank and access lids, assessment of baffles and pipes, measurement of sludge and scum layers, evaluation of the drainfield's condition, and recommended follow-up (pumping, dye test, or camera inspection if needed).
Milton-specific details: real estate transactions in Milton often trigger a thorough inspection to document system health in a rural setting with varied soil; some homes may require limited access to tanks or crawl spaces.
Typical cost in Milton: $150–$350 for a standard inspection; pumping may be added if sludge levels are high.
Resource: NH DES onsite wastewater information for inspections: https://www.des.nh.gov/organization/divisions/waste/on-site-water/index.htm

Drain Field Evaluation, Repair, and Leach Field Upgrades

What the service includes: soil absorption field assessment, review of percolation and drainage, trench or bed evaluation, replacement or repair of damaged trenches, and adjustments to improve drainage (e.g., repairing broken laterals or installing improved distribution).
Milton-specific details: sandy or gravely soils common in parts of Milton can affect percolation rates; deeper frost lines may influence installation depth and seasonality of repairs.
Typical cost in Milton: assessment/troubleshooting $600–$1,300; drain field repair or partial replacement $5,000–$15,000; full drainfield replacement can exceed $15,000 and rise with site complexity.
Resource: EPA septic system guidance: https://www.epa.gov/septic

Septic System Replacement or New System Installation

What the service includes: site evaluation, design planning, permit coordination, tank installation, drainfield layout, soil testing, and system startup. This is most common after repeated failure or on a very old system.
Milton-specific details: Milton's rural lots and variable soil conditions can drive design complexity and cost; access for heavy equipment and long-distance hauling can add to labor charges.
Typical cost in Milton: basic replacement or new system generally $15,000–$40,000+, with more complex or larger systems running higher.
Resource: NH DES onsite wastewater design and permitting overview: https://www.des.nh.gov/organization/divisions/waste/on-site-water/index.htm

Tank Lids, Risers, and Access Improvements

What the service includes: adding or upgrading risers and secure lids for easier access, sealing and venting improvements, and safety additions around the tank area.
Milton-specific details: frost heave and snow can obscure access points; risers help with winter serviceability in Milton's climate.
Typical cost in Milton: $300–$1,000 depending on materials and site access.
Resource: EPA septic systems information on maintenance and access: https://www.epa.gov/septic

Camera Inspection and Line Cleaning (Jetting) of Septic Lines

What the service includes: closed-circuit television (CCTV) inspection of the interior of lines from the tank to the drainfield, identification of blockages, and jetting or snaking to clear minor obstructions.
Milton-specific details: long driveways or narrow passageways in some Milton properties may require careful access planning, which can affect scheduling and cost.
Typical cost in Milton: camera inspection $150–$350; line jetting $150–$500 depending on length and accessibility.
Resource: EPA guidance on sewer line inspections: https://www.epa.gov/septic

Emergency Septic Service (After-Hours or Urgent Needs)

What the service includes: rapid response for overflow, backups, or system failures, with urgent pumping, temporary containment, and initial diagnostic checks.
Milton-specific details: winter backups are more common with freezing temperatures and heavy snowfall; after-hours service typically incurs a premium.
Typical cost in Milton: service call $100–$250 plus pumping or repair charges; after-hours fees may apply.

Routine Maintenance Plans and Service Contracts

What the service includes: scheduled annual or semi-annual inspections, pump-outs, priority scheduling, and alerts for sludge levels or equipment wear.
Milton-specific details: having a maintenance plan is helpful for homeowners with older or higher-use systems common in rural Milton properties.
Typical cost in Milton: $300–$700 per year depending on coverage and service frequency.

Permits and Compliance Assistance

What the service includes: guidance on local and state permit requirements, permit procurement support, and coordination with Milton's building or planning departments.
Milton-specific details: approvals may be required for new systems or major repairs; timelines depend on local review cycles.
Typical cost in Milton: varies widely; estimate $500–$1,500 for design, permitting, and plan submission support.

Official resources:

NH Department of Environmental Services (Onsite Wastewater Program): https://www.des.nh.gov/organization/divisions/waste/on-site-water/index.htm
U.S. EPA Septic Systems — Homeowners: https://www.epa.gov/septic