House to Septic line install

Old 10-10-17, 08:36 AM
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House to Septic line install

I am owner/building a custom home. The house is currently in design but I have gotten my septic permit. I need to install my septic system to get it grandfathered in before a neighboring property installs sewer. If I do not get it installed, prior to the sewer being installed, I will be required to extend the sewer at an estimated cost of $25- 30k versus $5k for the septic system.

Therefore I must install the septic tank before I know what the proper depth of the tank should be to maintain a 1/4" per foot slope. Unfortunately until my plans are completed and approved, I will not know what the finished floor elevation (it will likely be 18 - 24 inches above existing grade) will be and so cannot calculate the desirable depth for the septic system. The tank is supposed to installed at about 8 - 10' from the house in the front yard. My thought is to install the tank at the maximum permitted depth (based upon the bottom of the leach field being 4' deep). However I have read that having a slope on the sewage line of more than 1/4" per foot can cause problems by causing the water to flow too rapidly down the pipe and leave the solids behind in the pipe.

My thought was to connect the house sewage pipe to the septic tank pipe via a vertical pipe that would extend to the ground surface as a cleanout since a cleanout is required anyway. I would use a sweep 90 to connect this vertical to the septic line and a y-connector to connect it to the house line. Would this solve the issue? Is there a generally accepted method for connecting two sewage pipes that are at different elevations? Is there some other appropriate method I should use for solving this problem?

Last edited by sheebang; 10-10-17 at 10:01 AM.
Old 10-10-17, 09:45 AM
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Locally the health dept specs the septic system including where and how deep everything must be. Usually they must approve any changes from their standard specs. Another thing to consider is what happens once sewer becomes available. They rarely condemn a septic system but they often make you pay a sewer bill even if you aren't hooked up to it.
Old 10-10-17, 10:13 AM
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In my county the Environmental Services (Health) Dept. specifies how the system is to be built and where it should be located. The only way around that is to hire a Professional Engineer to design and spec out your system. If you get a gravity system you don't have to sweat the elevation much. Just determine the minimum elevations you need and put in some extra for a safety margin. Your line from the house to the tank must have a minimum slope but there is no maximum. Then if your house is higher or the septic tank is lower your drain line is at a steeper angle.

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