I’m not sure putting a valve on your gravity sanitary would be such a big deal. If you’re draining to a municipal main you should have a 6” gravity service that stubs out, usually close to the property line, but not always. I think a 6” valve, depending on the type, would be in the neighborhood of $300. I’d put it somewhere well onto your property so that if the municipality ever comes out to do work they won’t know about it. Preferably close to your clean out so if you do have to close it and there’s any debris caught on it, you can get a snake in to get the debris cleared and the valve closed all the way. Do you already have an idea of what kind of valve you’ll use?
***** “I’m not sure putting a valve on your gravity sanitary would be such a big deal. If you’re draining to a municipal main you should have a 6” gravity service that stubs out, usually close to the property line, but not always. I think a 6” valve, depending on the type, would be in the neighborhood of $300. I’d put it somewhere well onto your property so that if the municipality ever comes out to do work they won’t know about it. Preferably close to your clean out so if you do have to close it and there’s any debris caught on it, you can get a snake in to get the debris cleared and the valve closed all the way. Do you already have an idea of what kind of valve you’ll use?” *****
House is 60 plus tears old, don’t think we even have a clean-out (never had any problems so I never had to find it) I do know I cannot get Insurance since it is all Cast Iron in a Salty environment (bought the place 20+ years ago with an AS IS clause for Roof, Electrical and Plumbing, they built them good back in the day, just now need a roof)
We have huge Oak trees front and back, don’t know which direction the Sewer lines go, the House was in place before the roads, old timers tell me they remember when the back yard was on the corner of two trails and the dirt road was about 20 ft closer to the house (when planting trees in the front I did dig through Tar Balls and Oyster Shell) It was probably on a Septic System at first then tied in later so the City probably has good drawings, just haven’t invested the time as of yet.
When I do go find it ... thinking I will put the valve closer to the House, then the Clean-out both set in Concrete and accessible day or night.