We have a 900sq ft apartment in MA above our detatched garage that is plumbed in, has electricity but no sewage or greywater treatment. A couple of owners previous to us 25 years ago had installed a tight tank and the apartment was fully functional (kitchen, bathroom with sink, shower/bath and toilet). However they did this without the town knowing and when they sold the town had them crush the tight tank system.

We are on an old septic in the main house (limited to 3 bed, installed 1969) and are thinking about how we can get the apartment plumbed in so that:

1. The toilet works (there is an existing toilet).
2. The sink for kitchen (no need for dishwasher) and greywater water from bathroom can be dealt with.

The apartment is on MA recognized wetland, so we will likely have to get special permission to do any work when connecting outlets outside the building.

Considering:
1. Build an entirely new septic system away from the apartment that can handle the apartment and the house. I would expect that to run into the tens of thousands (maybe $50K+), but perhaps the ’69 unit will not last much longer.

2. Install some form of foaming / composting / incinerating toilet such as Clevus. Have a holding tank in the garage for the solids / whatever processing unit is necessary (there is room at the back). Also install a greywater treatment system that outputs clean water that we can simply drain away. Does greywater actually have to be treated in MA?

Has anyone done a similar kind of job?

Thanks