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drop manhole on sanitary sewer lateral

drop manhole on sanitary sewer lateral

drop manhole on sanitary sewer lateral

The gradient I'm dealing with to connect the sanitary sewer lateral to the main is too steep to run a straight pipe. That usually means installing a drop manhole. This is a residential scenario, so I'm envisioning going from the house at 2-3 fps until I get to the spot where I need to drop ~15' and then connecting up to the existing connection at the main. I'm hoping I can do this with a 4" cleanout to grade and not have to install a full on manhole structure. Would anyone like to share their previous experiences? Thank you in advance.

RE: drop manhole on sanitary sewer lateral

Does the local utility have standards/requirements?

What you suggests sounds similar to a "deep service riser" which is a local standard practice for connection to deep sewer mains.
Service enters top of the main. Restrained joints. No extension to the surface though.

RE: drop manhole on sanitary sewer lateral

Thank you - Right now service enters top of the main; I'm pretty sure. But it's exposed and I want to put it underground instead. You can see the lateral coming out of the side of the hill, continues for about 10 feet and then drops straight into the ground.

RE: drop manhole on sanitary sewer lateral

Is the sewer main in an easement? Is there no freeze issue? Then dig down about 4 feet on the riser. Cut it there, put on a 45 degree bend and lay pipe back toward the house , keeping the pipe 3-4 feet below grade.

Richard A. Cornelius, P.E.

RE: drop manhole on sanitary sewer lateral

Thank you - The main is in an easement. There is no freeze issue. A 45 degree (100%) slope seems like it would exceed the 10 feet per second flow velocity. To run the lateral direct from the house to the main would be around 39.7% slope which also seems like it would exceed the 10 fps flow velocity. I'm thinking of dropping 14' and running at ~1% to the main.

RE: drop manhole on sanitary sewer lateral

Putting in a drop manhole is not typical for a residential service connection.

I agree with CarlB that the service riser is the most common method to accomplish this service connection. See the attached sketch and confirm with the local utility.

Service lines usually have a minimum of 1% slope as you suggest until you reach the service riser.

Some communities also require a cleanout connection located near the building.

RE: drop manhole on sanitary sewer lateral

Thank you - I think I have what I need.

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