HDPE Directional Drill Transition

[sjohns4]

I posed this on the WasteWater forum since the pipes in question are force mains, but there are probably more HDPE drills used for potable water so the concept still applies:

I'm designing a replacement junction box outside of an existing pump station which sits next to a creek. There are two existing HDPE HDD lines (10" & 18" HDPE) crossing the creek which are connected to DIP which is anchored in a large concrete block. The client wants to eliminate all of the DIP and connect PVC directly to the HDPE pipes.

I've never heard of doing this, but wonder if there will be any problems, especially since the HDPE has been in the ground around 20 years.

Thanks,

Mike

 

[Zambo]

Not sure if I understood the question propoerly. Is the situation now Ductile Iron pipe connected to PVC pipes with the joint encased in concrete?

If my description is correct I think all you have to do is weld a flange connector to the HDPE pipe and make a similar connection on the PVC pipe, then bolt together. The only problem seems to be to remove the concrete block and then extend the PVC pipe to the new connection point. Alternatively you could install gate valves between the flanges and create a valve pit. But 18" valves are expensive.

 

[ODtape]

Take a look at the literature provided by Performance Pipe here:

http://www.cpchem.com/enu/performance_pipe_engineering_manual.asp

You will need to determine the pipe material. Standard water distribution pipe would probably have been PE3408. I don't think the age of the pipe should be an issue, but if there is any chance that the pipe has been contaminated with hydrocarbons, then fusion may not be an option for joining. You may need to use a mechanical connection, possibly with a pipe stiffener insert.

There is a variety of ways to connect HDPE to PVC, including HDPE flange and MJ adapters.

It sounds like the section of DIP was installed at the end of the HDPE run in order to facilitate some type of anchoring (?). The concrete block may have been installed to control expansion/contraction of the HDPE due to thermal or poisson effects. There are HDPE fittings available with integral flange-shaped collars for use in inline thrust/anchor blocks, so the DIP should not be necessary for this.