Using a reducer bushing on DWV Wye

[Nick Wombosi]

Can one use a reducer bushing on a 4x4" Sanitary Wye to tie in a 3" lateral line into a 4" main line ?
Both lines are horizontal with sufficient pitch.
If not, what is the correct way to tie in ?

 

[Breplum]

Broadly speaking adding a bushing to a branch on a sewer is fine.
However there are circumstances where it can be an issue, especially as it pertains to sewer jurisdictions that have their own rules.
For example, in multiple cities we work in, the sewer department prohibits any 3" drain runs longer than a few feet stubbed out of the dwelling, after the stub, the entirety of all sewer on the property must be 4" with no exceptions. With dug trenches, there are serious compaction and back fill support rules in place as well.
Consult your local sewer department before even digging.

 

[Sponsor]

 

[Nick Wombosi]

Broadly speaking adding a bushing to a branch on a sewer is fine.
However there are circumstances where it can be an issue, especially as it pertains to sewer jurisdictions that have their own rules.
For example, in multiple cities we work in, the sewer department prohibits any 3" drain runs longer than a few feet stubbed out of the dwelling, after the stub, the entirety of all sewer on the property must be 4" with no exceptions. With dug trenches, there are serious compaction and back fill support rules in place as well.
Consult your local sewer department before even digging.

Thanks. Could you explain what you mean by stub ? In this case, we have a 3" line coming from a bath about 10' under the house before going into the 4" Wye with a reducer. Everything downstream from that is 4". Ideally, I would have liked it to be a 3"x4" single piece Wye or combo. Not sure if using a reducer impedes smooth flow.

 

[wwhitney]

I believe breplum's comments were just about sizing, not about the use of a bushing vs a reducing coupling vs a reducing fitting. 4x4x3 wyes are available, if that is what you need.

Also, the term "sewer" refers to a buried drain outside the footprint of a building.

Cheers, Wayne

 

[Nick Wombosi]

Wayne, is using a 3" bushing on a 4x4x4 Wye kosher ?

 

[wwhitney]

I'm not aware of any code restrictions on doing so on one of the two inlets.

I also don't know if there are situations where it would perform better to instead use a 4x3 reducing coupling upstream, or a 4x4x3 wye.

Cheers, Wayne