Cost
If the lot is already on town sewer, the ADU still needs a connection from the building to that main. We price that connection after a site visit. We do not publish a hookup fee.
If the lot needs its own system, start with the prices that are on this site. Maine design starts at $700. A conventional system in Maine starts at $18,000. The soil decides whether a conventional system is enough. An engineered system or a pump system is a different design, and we price that after a site visit.
We do not publish a New Hampshire septic starting price. Call (978) 987-0089 and we will price the New Hampshire lot from the site.
Permitting
A septic job needs a town permit. Town permits vary. We do not publish a count of days or weeks for that review. The soil test, the application, and the town's review set the schedule. We will not dig while the permit is still open.
The same rule covers a sewer connection. The town has to accept the tie-in before we open the street or the yard.
A private system over the years
A private system stays with the house. You own the tank and the field. Pumping and repairs are yours. If the field fails later, that is a new look at the lot and a new price. We do not guess that date from a map.
A town sewer connection over the years
A sewer connection sends the waste to the town main. The town keeps that main. You still own the pipe from the ADU to the connection. A break on your side of that pipe is your repair. Any town fee comes from the town, not from a number we print here.
Which one you have
Sewer is the simpler long-term job when the main is already in the street. A private system is the job when it is not. We look at the lot and tell you which one you have. Then we price it.
The 2-minute calculator is on instant pricing. Published packages are on the ADU models.