Hello I wanted to run a few issues by you guys. This is a long post but I wanted to give you as much info as I could. I will also post a picture of my sump basin to help clarify.

First to describe my house. The front of my house is on top of a steep hill. The hill is about 20 feet above ground level. The right side of my house is also about 20 feet above ground level. To the left of my home we are about 5 feet lower than our neighbor The back yard is flat and about 3/4 of an acre but is also below my lefthand neighbor. My sump pump basin is located on the right or "high side" of this equation. The lawn on the left side and back of my house between me and my neighbor gets extremely saturated with some patches of stagnant water after a big storm.

The sump basin has 2 4" black lines that enter into it. During the past storm these lines were completely dry. Water was literally gushing in around them though through the hole that was made to allow the lines to enter the basin.

I bought the house used but it was built in 2006 and is relatively new construction. It is 3500sq ft. There are 6 rain spout drains that "disappear" into the ground and are not daylighted anywhere around my house. They do go into the same type of black 4" pvc but it does not seem to be the same 4" line that ties directly into the basin since the line entering the basin is dry. I can also say for sure that they are not backing up with water in any way.

I do not believe they are tied into the storm sewer but I suppose they could be. Honestly I believe they are not and are likely somehow connecting back to the sump basin.

Regarding the 2 4" lines in the sump basin:
Since I was not around when this was built I do not understand the grand plan with this. Are these lines possibly drain lines that will empty the sump if the water reaches them? My sump pump was running about 40 out of 60 seconds per minute in short bursts to keep the water out. I have a battery backup but I doubt it could last that long if I lost power so I am trying to come up with a real solution to the issue.

After the storm we were still taking a fair amount of water. I disconnected the sump pumps to see what would happen if the water ever reached these black 4" lines. The water did not reach the lines. Basically the sump basin filled up to the point where water was entering the basin (right below the black pipes) and then stopped.

All of this leaves me to a few questions:

#1. Any clue what the likely intention of these black lines were and why there is no water entering them?
#2. Why would the water stop entering the basin once it reaches the point of entry? Is it simply finding another way out from under the house, or once it reaches this level does it start backfilling under my house and simply rise at a much slower rate, ultimately leading to a flooded basement after time has passed.

#3. From a drainage perspective, I believe I could run a slightly angled pipe directly out the bottom of the sump pump basin through the hill that my home sits on and still be above ground level. Can this be done? I don't understand why it wouldn't have been the default approach thus eliminating the possibility of a sump pump failure. Is there an issue with cutting the hole for such a line in a basin that never intended for it to be there?

Given that my house sits this high I am confused as to why I would be taking on so much water. My only guess is that it is a combination of the neighbor’s elevation but also possibly my gutters draining directly into the basin. It seems like a large risk for them to have planned for the gutters to drain into the basin though and I am not sure if that is something that is typically done. Also I would have expected the gutters to be draining directly to those black pipes that enter the basin. It seems as if the water is getting from the gutters to the basin in slightly less direct means.

any insight is welcomed. This is my first house and I am clueless.