gravity fed sewer line basics ???

[graysilm]

Hello. I am wanting to run sewer to my detached garage. The garage is in the back yard and is lower than the house. I do not want to install a pump system. I would like to run a sewer line around the house and tie into the house sewer line in the front yard. This will require a few 45 degree angles. I am also not sure of the fall I need. Some people say 1/4" per foot and others say 1/8" per foot. Where can I get some basic info on fall and the impact that having angles in my line has. Thank you

 

[LLigetfa]

You don't say where you live so local codes may vary. Here my plumbing inspector frowned on side bends on the same plane, insisting I roll the elbow for additional fall.

 

[Sponsor]

 

[Jadnashua]

Generally, the larger the pipe, the lower the pitch you can live with. Often, that break point is 4". Obviously, the smaller the pitch, the harder it is to ensure there are no dips or rises - the pitch must be maintained over the entire length, not just end to end. You need to verify with your local inspector what he wants. WIth the typical pvc or abs pipe you'd probably use, it is really easy for it to bow or droop unless you are extremely careful about prepping and filling. This can easily mess up the flow, create blockages, and really mess up your day. More slope makes it easier, but you have a certain end point. Depending on how deep the sewer line is at the street, or where you can intercept it before, you may not be able to use gravity - you may end up with a pumped system.