Concrete Retards for Pipelines 2

[alanpaustin]

I'm installing an 8-inch water transmission using C-900 pipe. I've seen criteria for concrete retards for sewer pipe and drainage pipe with slopes in excess of, say 12%. I am not aware if retards are required for potable waterlines. Any comments?? My route will have slopes of up to 40%.

 

[rconner]

I suspect piping on steep slopes can sometimes represent quite rugged installation and service challenges, and even in some utilities that allow plastic piping, ductile iron pipe only, and that often only fully "restrained" is required (see e.g. the utility specification on site

http://www.mnwd.com/Spec Plans/sec 500.pdf

pg 500-1 "...500.3 TYPE OF MAIN PIPE
Residential Areas (Distribution Mains). Only C-900 P.V.C. pipe, Class 200 or ductile-iron pipe, Pressure
Class 350, is to be used for distribution mains of 6 inches thru 12 inches in diameter. Only ductile iron pipe
shall be used for 4-inch pipeline. For 16-inch diameter pipe, pipe must be ductile-iron pipe, or CML&C steel
pipe... Fully restrained DIP shall be used within easements with restricted access and slopes exceeding 10%...)

I have also noticed the 1997 version of the "Ten States Standards for Wastewater Facilities", in Section 33.46 pg 30-3, contains requirements for "concrete, or equal, anchors spaced..." at increasingly closer intervals as sewer slopes increase between 20-35, 35-50, and 50 percent or more.

I think what they are conceivably talking about are essentially concrete piers immediately behind the bells that are often laid ahead up a hill, such as is pictured at

http://www.acipco.com/international/engineering-data/poss.cfm

(I suspect such pier anchorages help to anchor a pipeline against any downward movement, and perhaps additionally don't hurt in the stability or erosion potential of some inevitably disturbed trench backfill soil on steep slopes as well). When pier supports are used underground, some design principles as noted at

http://www.dipra.org/pdf/pipeOnSupports.pdf

can be used analyze any effects on thickness design of the pipe itself.

 

[mflam]

rconner has given you all the info you need to make a good decision here. I would just add that 40% is a pretty tough installation. I would be looking at restrained joint pipe for the peace of mind. I hope your budget is not too tight.