Storm water piping question

[stokton12]

I know if you have an mainline urban pipe system, running/flowing a certain directioning down a highway, SW pipes connecting in from sites should be bearing the same direction, being perpendicular at worst. Is there much tolerance for the tie-in pipes being off-perpendicular in the other direction?

Example: If you have a mainline longitudinal pipe running/flowing east, can you tie in an outfall pipe from a SW pond to the system bearring slightly west, like maybe 10 degrees from being perpendicular?

 

[Ron]

You certainly don't want to do this. If the main line flow is always greater than the connected flow from the pond, you'll never get anything out of the pond! The main line flow will try to go back into the pond pipe.

To correct, if you have the elevation room, you could drop the pond pipe in from the top, not the side. That way the main line would have to be flowing completely full to impede the pond pipe outflow.

 

[LittleInch]

You're new here, so I'll cut you some slack, but please don't double post - it's against the site rules and people really don't like it.

It would help greatly if you could provide a plan and elevation sketch - hand drawn is OK, scan it in and attach via the link at the bottom of the posting box. Makes it much easier to respond.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[stokton12]

Thanks Ron.

LittleInch, noted.

 

[cvg]

without plan and profile it is really impossible to predict the hydraulic performance of your system. backing up may or may not be a problem. coming in at 100 degree angle will cause some head loss, just calculate the loss and add it into the junction loss. amount of head loss will depend on the flow rate and velocity in the pipes and will be slightly more than if you came in at 90 degrees.

 

[bimr]

Agree with cvg. Without plan and profile and function (trunk or interceptor sewer), the question is impossible to answer.

Without a profile, you can no determine if a surcharging sewer (also unknown) would backflow the lateral.

In general, storm sewer alignments between drainage structures (inlets or manholes) shall be straight. The angle of confluence where pipe centerlines intersect shall be 90 degrees or less. In addition, the change in the energy grade line through the junction shall not exceed 3 feet.

Most cities would probably not accept the proposal on a trunk or interceptor sewer.

 

[dicksewerrat]

You could run your line to a point 15 feet from the mainline. Build a manhole and turn your line 15-20 degrees so the lines intersect at an angle going with the flow. into a new manhole on the mainline.



Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[stokton12]

dicksewerrat,

That's the only real solution we found, even though it'll cost a little more. We were trying to avoid tying a SW pond outfall pipe in to a blind junction box downstream in the highway. The nearest visible junction was a curb inlet slightly upstream. But we'll just add a junction box between the outfall box and the pipe mainline to turn it in the proper direction.

 

[dicksewerrat]

Have you gotten permission to connect to the curb structure?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com