3-inch force main

[jartgo]

Need to use a 3-inch force main, almost 3 miles long. SDR 21 comes in 3-inch but obviously not common. SCH 80 is readily available in 3-inch but not sure if the belled end SCH80 is readily available.

I have two questions:
1) Do you concur with the SDR21?

2) What type of fittings would be used?

Thanks in advance, I'm not overly familiar with the small diameter stuff.
JT

 

[rconner]

fyi

http://eng-tips.com/viewthread.cfm?qid=238327&page=2

 

[shirsch]

Use HDPE

 

[rconner]

fyi also

http://eng-tips.com/viewthread.cfm?qid=124331

 

[dicksewerrat]

I'd look at directional drilling the line in, using HDPE pipe.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[redbridge]

3-inch sdr 21 is fine and is common. Use ductile iron fittings. The only problem with HDPE is that some of the utilies do not have the equipment to work on the pipe.

 

[rconner]

This may be a stupid question, but if 3" size pipe is "fine" for such a long forcemain, why do the Ten States Standards for Wastewater accessible e.g. at

http://10statesstandards.com/wastewaterstandards.html#49,

along with a great many other local and regulatory agency specifications in many other areas, say, "The minimum force main diameter for raw wastewater shall not be less than 4 inches (100 mm)"?

 

[jgailla]

rconner,
That statement in Ten States is based on a standard pump with a throughlet of 3" minimum. If a grinder pump is used, sizes less than 4" are acceptable. Ten States is geared more toward larger public mains, not small projects with low sewage generation.
If the pump is not a grinder pump, I would agree with you that a 4" force main is required, unless the regulatory body in that state doesn't invoke Ten States (I think there are only a couple, if any, that don't).

 

[jartgo]

I concur with jgailla, the Ten States rule of a 4" minimum doesn't consider a provision for grinding. In my area, if grinding is not used, a 4" force main is the smallest allowed and the pump must be capable of passing a three inch solid.

 

[semo]

The SDR 21 is probably your cheapest.

Being a forcemain, I wouldn't worry too much about having to work on it. You can call out for the HDPE to be DIPS or IPS in size and therefore can get ductile iron fittings to work on it. The cost of the pipe will be a lot higher however, and depending on your route, the installation cost could be higher.

 

[rconner]

I didn't happen to see in the original inquiry that this was a grinder pump only design, and while I agree Ten States does require pumps that will pass 3" solids I don't otherwise read the specific gearing nor allowances you refer to in the Ten States Standards document. Nevertheless, I understand the arguments you are making, and I guess as long as the regulators and funders etc. involved are happy that the grinder pumps and very small pipes you recommend are the way to go, I guess you are OK (unless there are problems with the grinder pumps or stoppages/other problems with the very small pipes, or you evntually require increased future capacity -- see also

http://books.google.com/books?id=LV...X&oi=book_result&resnum=2&ct=result#PPT385,M1

).