Infiltration into 33 inch pipe

[dicksewerrat]

We have a 33 inch sanitary main leaking 4 gpm through a 1 inch diameter hole. what formula can I use to get the head pressure driving the infiltration?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

Would that the elevation of the ground water above the leak should be correct. If you don't have that, estimate it from ground level.

 

[cvg]

orifice equation

 

[rconner]

While I don't think you have given enough information to really use any "formula" (for example for "discharge" through an orifice etc) with any accuracy, my guess is that you may well not even be flowing through all the area of the 1" hole, further complicating analysis. Perhaps this means you either have some dirt obstructing it from the outside of the pipe, or you have VERY little driving external head. Let us know what you find out.

 

[bimr]

Must be smaller than 1-Inch as the orifice calculator predicts 6 gpm with only 3 inches of head.

 

[dicksewerrat]

That leak is at a joint. But it seems to be flowing from a smaller are and it projects about 6 inches into the pipe. Ground water to the surface would give me 40+ feet of head. Thanks for the info.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[cvg]

you may have 40 feet of static head, but likely a lot of friction loss in the soil in order to flow at 4 gpm. 4 gpm is a lot of flow for groundwater, it might indicate a leaky watermain or sewermain or storm drain in the area.