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Question DetailsAsked on 11/23/2014

How much to install a small septic for garage

I want to install a small septic system for a small one room garage apartment ,who should I call,and about how much will it cost

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3 Answers


Depends a great deal on local soil permeability, whether you are the required minimum distance from property lines and adjacent wells and open waterways or drainages, etc - but probably about $3-5000 range would be a fair average target number, though could run from more around $1500-2000 at extreme low end under ideal conditions in a low cost area to $5-25,000 in an area where you have to build a raised mound or advanced system due to permeability or distance limitations or steep hillside conditions. I even did one for an in-law detached guest house once in tight constraints from adjacent wells, with the tank near the other tank (which was up to legal size for house occupancy) and the leach field as a raised bed on top of the main house leach field,, which did have enough infiltration capacity to handle the extra flow. That assumes a second system on one lot is legal in your area (not so in many areas), and of course that the garage apartment is also legal in your area.

In most cases, it would almost certainly be cheaper to run the sewage to the existing septic system for the house, especially if it can be done by gravity but if not still probably cheaper even with a lift pump, and almost certainly even if additional legs have to be put in the leach field. The only way I see it probably being cheaper to put in a separate system is if the existing system is maxed out with respect to legal tank and field size with the existing house, or is old and having problems handling larger flows.

Your starting point is determining (probably Planning and Zoning department,maybe Building or health department depending on area - see who issues septic permits) to see if you can even do it (apartment and second septic system both), then a Civil Engineer licensed/certified and experienced in septic system design. AL does not appear to have a Search the List category for that - Septic Tank is the closest but that is probably all septic tank installers and pumpers. Try the local yellow pages or google for Civil Engineer - Septic Design in your area.

Answered 5 years ago by LCD


I agree with LCD

in our state, septic system installers must be licensed and as such also become design/build artists = the go to business to solve this issue you have.

The rest of the industry have become simply conceptual in this issue when assessing site potential for a project w/caveat that the septic guys will have the last word on that issue.

Answered 5 years ago by tgivaughn



This is Kelly M. with Member Care. Thanks for posting your question.

Although we don't track going rates for various projects because this varies widely depending on market factors and location, members are encouraged to include how much a project cost in their reviews.

With that in mind, a good way to find out a general price range, login to your membership and search for Septic Tank, and then look as the project cost associated with each review. The best way to get the most accurate information is to request multiple bids from several local contractors. As the price will vary with work site considerations and individual contractors' approaches, getting multiple estimates will help provide a clearer idea of what to expect in terms of pricing.

I hope this information help! Please let me know if I can assist further. You can respond to this thread or submit a new Answers post. You can also reach us at

Thanks again, and have a good day!

Answered 5 years ago by Member Services

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