4" Sewer Line

[RedBauer]

I'd like to see some experiences and opinions on the following question. What is the maximum distance a septic tank should be placed away from a building while utilizing a 4" SDR-35 pipe with 1/4 inch per foot slope?

We haven't encountered any maximum distances before and New York State doesn't specify anything. We designed a system last year and we're trying to see if we placed the septic tank too far from the building. The building referenced has a design flow of 480 gpd and is an Operations and Maintenance building.

 

[bimr]

The maximium distance will be a function of how easily the sewer can be cleaned.

You have a 2% slope which is adequate for the application.

One would expect that you should be able to place the septic tank 200-250 feet away without difficulty. If you have concerns, you can install additional cleanouts.

 

[cvg]

how about depth? the farther you move it away, deeper it gets. At 250 feet, top of the tank is about 6 or 7 feet deep and the bottom of the tank is much deeper. At some point you might hit bedrock or water table, at the very least it will be a deep excavation to install the septic tank.

 

[RedBauer]

For this situation, the slope of the land exceeds the slope of the pipe. Therefore, the max distance we could put the tank was approximately 75' from the building. We were trying to rule out all options, but we believe frost is what burned us on this situation. The lack of cover on the pipe near the septic tank along with an uninsulated pipe makes for a bad combination.

 

[bimr]

What is the problem that you are having? How deep is the sewer?

 

[RedBauer]

We have adequate cover near the building (maybe 42-48" cover). Near the septic tank we have 12-18". We might have been fine if this area was grass covered, however it was an Item #4 driveway.

We believe the frost caused the pipe to freeze in the 12-18" cover area. The pipe wasn't insulated or encased in a SCH-80 pipe for protection. There was an approximate 40' section of solid ice in the pipe. Thus, they could flush their toilets.

 

[bimr]

You will have to consider the installation of an insulating board above the sewer. Minimum depth of sewers should be 2-3 feet depending on location.

 

[dicksewerrat]

Frost pentrates deeper under roads.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com