Connecting PVC pipe to existing storm sewer - not in a manhole 1

[HEHurst]

I'm working on a plan that includes the need to connect a new subsurface drain line (likely 8" PVC) to an existing 18" concrete storm sewer. There is no manhole at the connection location, and a new one cannot be placed there.

So I believe the best option for making the connection is to expose the top and/or side of the 18" storm sewer and have the contractor simply drill out a hole to tap into with the PVC (depending on final design, will either come straight into the side with the PVC pipe or drop down from the top with a fitting).

Is it reasonable to assume that most underground/utility contractors will have the equipment to drill through the concrete storm sewer? (this connection will likely be the only concrete work on the job) I'm assuming some sort of diamond-blade hole saw is used, right? Is the same sort of saw also able to cut through rebar if encountered? (don't know if the storm sewer is reinforced or not, so I'll assume it is)

Would some sort of grout be used to hold the PVC in place in the storm sewer opening? Any recommendations on specs for the grout? I imagine it's key when cutting the opening in the storm sewer to minimize the gap between the outside wall of the PVC pipe and the opening in the concrete.

I probably will have this connection be a separate bid item in the construction contract. Any guidance on typical unit prices to expose the concrete storm sewer (it's about 4 feet deep, under grass), drill through it, and connect the PVC drain pipe)? There will just be one of these connections on the job. Or would this typically be "incidental" to installing the rest of the PVC pipe?

Thanks!

 

[PELS]

Yes, the contractor can core drill the RCP main and install a grouted RCP fitting then connect the PVC lateral to the fitting with an adapter.

Also scroll down to Details S-2B and S-10 here for an example:

http://www.ci.livermore.ca.us/eng/documents/SanitarySewerandStormDrain_000.pdf

 

[Maury]

Use Inserta-tee (insertatee.com). It includes a pvc hub with rubber sleeve and stainless steel band. A hole has to be core drilled into the pipe. If the utility contractor doesn't have the equipment, he should know where to rent it or who to hire.

I'd probably make it a pay item.

 

[bimr]

Where a wye or tee is not provided, a tapping saddle designed for use with RCP may be used, or a section of pipe may be removed and a wye or tee installed. You can use the Inserta-tee or a saddle. Consult a concrete pipe manufacturer.

Furnish and install one (1) 18" x 12" saddle, complete as specified, each. Furnish and install one (1) tap into existing 18" RCP storm sewer, complete as specified.

Differential settlement is possible with a mortar joint; settlement may result in the pipe being sheared or cracked at the connection. Inserta-tee or saddle connectors that are available provide some flexibility between the connections.

 

[Drumchaser]

"If" at all possible we run the subsurface drain line to a catch basin, curb inlet, or culvert headwall.

 

[cvg]

cutting an 8" hole into an 18" pipe will unacceptably reduce the strength of the larger pipe. Also, these holes are generally not "drilled" but cut with a circular saw fitted with a diamond blade. It may not end up being a very close fit. I would recommend either cutting in an 18"x8" RCP tee fitting or placing concrete encasement around the entire connection to prevent the cracking and shearing alluded to by bimr. Since the concrete encasement will shrink, a mastic seal and waterstop is often also used to prevent leakage at the joint.

 

[dicksewerrat]

Who owns the existing 18 inch pipe? They will tell you what you will do to connect. You will not tell them.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com