Septic drain add-on question.

[flickit]

Want to add an additional drain line to a septic tank at the point outside the house where a vertical above ground cleanout and a below ground 'Y' or sanitary tee connects to the main house drain and is then outputted to the septic tank. Material is ABS and was wondering what the best way is to add the additional 'feed' without having one back feed into the other? Any other gotchas that might arise? Additional line is a long haul 100+ feet from detached garage with at least 4 feet of fall from garage to cleanout. Drain is 4 inch ABS with a sink, tub/shower combo and water closet attached. Usage is minimal and sporadic (detached garage is being converted into a guest house).

[mdshunk]

Septic systems are sized to the number of fixtures draining into them. When you start adding to a septic system, you can be asking for trouble. I'm surprised they didn't mention this when you pulled the permit. Adding an addition on a house or adding a guest cottage often necessitates installing a larger or another septic system.

[flickit]

Septic systems are sized to the number of fixtures draining into them. When you start adding to a septic system, you can be asking for trouble. I'm surprised they didn't mention this when you pulled the permit. Adding an addition on a house or adding a guest cottage often necessitates installing a larger or another septic system.
...fairly open-minded and explained that it isn't the number of fixtures (or more commonly; the number of bedrooms) but the number of occupants. We are going to increase the septic tank size and add the required leach pipe.

[DUNBAR PLUMBER]

If I read your initial question right, I will just state it like so;


You cannot tie into that vertical upright for the cleanout. You can tie into that sewer line before or after that cleanout with a wye and use the appropriate fittings to either jump up to the new piping or connect to it at the same depth as the wye is.


Make sure that you install a cleanout at the point of tieing into the system, even though you might have one in close vicinity. Should be a code requirement.