I didn't post this thread in the plumbing section because I know how to run the pipes, but here's my situation...

I just finished installing a French drain system that connects into a previously installed sump pump pit just in time for Hurricane Irene. My Hydromatic pump has been working overtime ever since. At one point the water was too much for the pump to handle and I suspended a second pump into the pit using a 2x4 and a bungie cord. It did the trick but I need something a little more permanent. So very soon I will install a backup sump pump that is powered by city water. My problem is I'm not sure where I should run the secondary discharge pipe. I just know that I don't want to connect the backup discharge pipe into the primary one.

The ideal place for the secondary pipe to end would be exactly where the primary pipe ends... A storm drain out by the road. My town gave me permission to tap into the storm drain below ground level so the pipe is completely hidden. However, after I laid that pipe I installed a 4" thick concrete walkway above the pipe. If I dig a tunnel under the walkway for the second pipe I'm afraid that I will weaken the base and cause a crack to form during the winter months.

The other option, and less ideal one, would be to run the secondary pipe out the back of the house. My property is relatively flat and my neighbor's yard is behind mine. I would have to end the pipe a few feet away from the fence and attach a pop up cover. This would lead to pooling, but the pipe would end about 25' away from my house. I figure this would only happen once or twice a year so I can live with that. What makes me nervous about this option is that since my sump pit is near the front wall of my house, the discharge pipe would have to be attached to the basement ceiling joist for about 25' before it exits out the back of my house. I'm confident that my installation would not result in a leak, although it would suck if a leak did occur, but I also run the possible risk of dealing with an annoying water hammer from the check valve.

So what do you think is the lesser of two evils... Going under the concrete walkway or out the back of the house? Thanks.

Go under the sidewalk. Jet a hole with a pipe and a garden hose, sleeve it with a 2-3" pvc pipe and run your discharge pipe through it. What size is the discharge pipe 1 1/2"

The discharge pipe is 1.5". What is the hose for?

To jet a hole under the sidewalk, put a piece of pipe on the end of a GARDEN HOSE with an adapter, attach a high pressure sweeper nozzle and let high pressure water cut a hole under the sidewalk. We've done this with EMT to dig holes for piers when installing a dock or walkway. You can dig it if you want but this is easier when going parallel to the ground. Then, put a 2" pvc sleeve under the sidewalk and slide your drain pipe through. That way, the pipe helps support yhe sidewalk without it settling on your discharge pipe.

Under the concrete I have about 4" of compacted item 4. Will this method still work? Also, should I tunnel next to the other pipe or should I leave some room?

I'll assume your Item 4 is #57 stone or something a bit larger. That will be a problem. In that case, I'd probably cut a strip out of the sidewalk, install the pipe and pour a patch. You can do side by side, the pipe sleeve will support well. Wonder what kind of flow you could achieve with a wye connection and 2 pumps. Is the pipe under the sidewalk in a sleeve?

I'd really rather not cut the sidewalk because it is only 1 year old. I didn't sleeve the first pipe because it would have stuck up past the gravel and possibly created a weak spot in the concrete. My property is almost completely flat in the front yard and getting proper pitch for the pipe was difficult. That's why the original pipe was not installed any lower.

Sounds like your question is how to get under your sidewalk without causing a crack. Jetting a hole works well but it can lead to cracking as you have no control of the hole size being created. I recommend driving a steel pipe larger than your discharge pipe through the substrate under your sidewalk. Galvanized fence posts are an economical choice, just drive it through with a sledge hammer and a heavy block of wood on the end of the pipe to distribute the force evenly around the edge of the pipe, it will take some time and both ends of the pipe will be damanged to some extend by the time you drive it all the way through. Simply buy a piece that is longer than you need and cut off the damaged ends after you have it installed, then clean out the inside of this pipe with the water jet technique discussed above or just use a long steel bar, crow bar, railroad bar, or a piece of rebar. Then you will have successfully installed a bore casing. The same technique is used by utility contractors, although they will use a directional boring machine that will pull the casing back as the bore bit is retracted, the result is the same.