Sewer pipes 10-14 degrees out of alignment

[Joseph Skoler]

I just discovered that a house I just bought has a 4" SDR 38 sewer pipe at a small angle (approximately 10-14 degrees) off from the inlet to the septic tank.

I know that straight is best, but I don't know how to achieve that.

Here are a couple of pictures.

Any suggestions would be greatly appreciated.

Thank you!

 

[wwhitney]

Sounds like an 11.25 degree elbow (1/32 bend) would do the trick. Any remaining deviation you could make up within the Fernco coupling(s).

SDR-38 is a new one to me. More common are SDR-35 and Schedule 40. SDR-35 4" is 4.215" OD with a minimum wall thickness of .12" (that's 4.215" / 35), for an ID of 3.97" or less (if the wall is thicker). Schedule 40 is 4.50" OD with an ID very close to 4.0". I'm guessing that SDR-38 will have the same OD as SDR-35 and be compatible with SDR-35 fittings. But you should take some calipers and carefully measure the OD of the SDR-38, as well as of the septic tank inlet, to see what you need.

4" Ferncos are designed for Schedule 40 but you can crank them down to SDR-35; I prefer to use a bushing on the SDR-35 to increase the OD to 4.5". That's sold as a separate part, or the bell end of a SDR-35 solvent weld pipe can be used to make the bushing.

A brief search did not turn up any SDR-35 solvent weld 11.25 degree elbow. They are available as gasketed SDR-35 fittings, as well as Schedule 40 fittings.

So if SDR-38 OD = SDR-35 OD, you could use a gasketed SDR-35 11.25 elbow, plus a short length of SDR-35 pipe, plus a Fernco on the septic inlet. Or if the dimensions are off, I'd suggest using a Schedule 40 elbow, two stubs of Schedule 40 pipe, and two Ferncos. In each case ideally adapting the OD to 4.5" for the Ferncos.

Cheers, Wayne

 

[Sponsor]

 

[Joseph Skoler]

Hi Wayne,

Thanks very much for the help and education.

I went ahead and used two 22.5 degree sched 40 elbows and then a coupler to the mysterious SDR 38. Primed/Glued the whole thing and did not need any ferncos.

I hope I did well.

Here's what it looks like:

 

[wwhitney]

That works great as long as you confirm that each segment still has the proper slope. I didn't suggest that because I was concerned about the slope on that pipe between the two elbows, and whether it might end up too shallow, or require more drop than you have available. But that may be a non-issue in practice, I'll need to think about that some more.

Also looks like you went back farther upstream so that you could put a little angle at that new upstream coupling, and also give yourself some more adjustability at the septic to get the double 22.5s to work.

Cheers, Wayne