Title 5 Inspection in Plympton, MA

Plympton is unusual even by Massachusetts standards. The town states it plainly in its own regulations: there is no public water supply and no sewer system, so all residential, commercial and agricultural wastewater goes into the same aquifer that supplies the town’s drinking water. No suitable community well site has been identified.

That situation produced a set of supplemental Title 5 regulations that are among the strictest in Plymouth County. Where the local rule and the state rule disagree, the stricter one governs. If you are buying, selling or renovating in Plympton, the differences below are not fine print.

No New Alternative Systems Since March 2021

This is the single most consequential rule in Plympton and almost nobody knows it until they need it.

No new alternative or innovative septic systems have been permitted in Plympton since March 9, 2021. The town’s reasoning is stated openly: alternative technologies require a high degree of maintenance and oversight, Plympton does not have the resources to provide that oversight, and some of the technologies in use have not proven long term reliability.

Why it matters: on a constrained lot elsewhere in Massachusetts, an alternative system is often the thing that rescues an otherwise impossible replacement. In Plympton that option is gone. If your system fails and the lot is tight, you are working within conventional design or pursuing a Local Upgrade Approval from the Board of Health. Find this out before you commission an engineer who assumes otherwise.

Sizing Rules That Exceed the State Code

• Minimum leaching area of 750 square feet for up to and including four bedrooms. Then 1,000 for five bedrooms, 1,250 for six, 1,500 for seven, adding 250 square feet per additional bedroom. For comparison, neighboring Kingston requires 800 square feet as its floor. These towns share a border.
• Every soil absorption system serving a single dwelling must be designed for a minimum of four bedrooms, regardless of how many the house currently has.
• Minimum design of 110 gallons per day above the required bedroom design, and a minimum of 440 gallons per day for any dwelling unit.
• Any upgrade or replacement requires a minimum 1,500 gallon septic tank.
• Garbage disposals carry a heavy penalty. With a grinder installed, the tank must hold 200 percent of design flow with a 2,000 gallon minimum, and the leaching area increases by 100 percent. If you are planning a Plympton build, think hard about the disposal.

Groundwater Separation and Mounded Systems

For new construction on any lot under five acres, Plympton requires a minimum vertical separation between high groundwater and natural grade of four feet where the percolation rate exceeds two minutes per inch, or five feet where it is two minutes per inch or less. The same applies to any upgrade that increases design flow.

Mounded systems for new construction are restricted to lots of five contiguous acres or more. On a smaller parcel with high groundwater, that combination is genuinely limiting, and it is the reason some Plympton lots are harder to build on than their size suggests.

Before a Perc Test Can Even Be Scheduled

Plympton will not book a percolation test until three conditions are satisfied:

1. All outstanding fees and taxes owed to the Town of Plympton are paid.
2. The Conservation Commission has completed a site review.
3. Wetlands are flagged, where necessary, by a certified botanist.

Each of those takes time on its own. Discovering them sequentially rather than in parallel is how a Plympton replacement slips from weeks into months. Note also that percolation tests performed before January 1, 1996 are invalid, so an old test in your file is not worth relying on.

Four Inspections Before a Certificate of Compliance

The Board of Health or its designee must inspect at four separate points: the percolation test, the excavation before stone is placed, the fill inspection where material is removed and replaced, and a final inspection before backfilling. Work waits at each stage.

The as built plan must show all setbacks required by Title 5 plus the location of the well, be stamped and signed by the designer and signed by the installer. Two paper copies come from the installer and one PDF from the engineer before the Certificate of Compliance is issued.

Installers must hold a current Plympton permit, which expires on the last day of each calendar year. Installing without one carries a $1,000 fine plus double fees, and the Board will not let an installer in violation start another system until the original issue is resolved. Worth confirming your contractor is currently licensed in Plympton specifically.

Setbacks and Well Water Testing

Plympton sets its own setback table, measured in feet for the septic tank and the soil absorption system respectively: property line 20 and 20, in ground swimming pool 20 and 20, above ground pool 10 and 10, private water supply 100 and 150, irrigation well 50 and 50, surface drains and wetlands 50 and 50, subsurface drains and road catch basins 50 and 50. Where more than one setback applies, all of them must be met.

Any new building in Plympton requires well water testing collected by a state certified lab, with satisfactory bacteria and general chemistry results, plus an EPA Method 524 test where the Board of Health requires it. Piping must be Schedule 40 PVC or better and distribution boxes must be watertight concrete.

Plympton’s current regulations also incorporate MassDEP guidance on Title 5 compliance for accessory dwelling units dated April 7, 2025. If you are considering an ADU, septic capacity is usually the binding constraint, and it is worth checking before you draw plans.

Common Questions

My Plympton system failed and my lot is small. What are my options?

Because alternative systems are off the table, the realistic paths are a conventional replacement if the site allows one, or a Local Upgrade Approval from the Board of Health that brings the system as close to full compliance as the lot permits. Ask about the Local Upgrade Approval by name.

Can I reuse my reserve area without a full engineered plan?

Only if the existing system is 15 years old or less and a design plan showing the reserve area is already on file with the Board of Health. The replacement must match the original or an approved equal designed by a professional engineer or registered sanitarian, and a bottom hole inspection is required.

Does Plympton test my well water at sale?

The stated requirement applies to new buildings. That said, with every home on a private well drawing from the same aquifer the septic systems discharge into, water testing at transfer is sensible regardless of whether the town compels it, and most buyers ask for it.

How long is a Plympton Title 5 inspection valid?

Two years, extending to three if the system is pumped annually and you keep the records. The state rule applies here as everywhere else in Massachusetts.