Concrete sewer pipe penetrations 3

[blowhard]

We are planning to add two new 12" SCH 40, CS laterals to an existing 24" RCP. Is there a limitation on the hole size that can be bored in a 24" pipe?
The laterals are dischrge lines from two new oily water separators. We don't have adquate spacing for a box and manhole at the tie-in points because of other underground lines in the area.
We plan to bore the 13.75" holes at 45 degrees and grout them in. Then build a form and pour concrete around the laterals for strength.
Any other suggestions? Thanks.

 

[BobPE]

The short story, without knowing everything about your project, I would say you should not do the connections that way. Your connections should connect to a new manhole(s) constructed on the 24-inch main and if you don't have the room, you should consider realignment of the main. Coring and grouting the connections is only asking for trouble. If we knew more, maybe a saddle could be used. Try searching for a firm called GENCO.

let us know how you make out...

BobPE

 

[dicksewerrat]

If you can expose the pipe, install the coring machine at an angle and then install the pipe, you have room for the manhole. If it is in and on your pipe, you can get by with a 36 inch manhole.

 

[DRC1]

We have done this on ocassion. It is not the prefered approach. The biggest problem is clearing a clog where the two pipes join.
Generally you would expose the pipe at the pentration and mark and line drill the penetration, making it somewat larger than the new pipe. Set the new pipe in, leaving space all around the between the old pipe and new pipe.
Chink and mortar the joint (not grout, as grouting will blow though into the old pipe). Once the mortar has set, dig below the old pipe, from the sides and top and pour a 4-6" thick collar around the joint. One important point, make sure upstream of both pipes is plugged before starting.
Again unless it is temporary such as to cut in a line,however, if you can avoid it, I would go with the manhole. It is not that significant a cost savings up front and if you have a problem, it could be very expensive.

 

[blowhard]

Thanks for your helpful responses. You convinced me to install a new box. I appreciate your help.
BH