Guys, I need some help on an area I have not much experience with. Let me give you the rundown and background behind the situation:
I recently had my back yard covered with a 5" reinforced concrete patio (approx. 18' x 25').
My property is 20'x100' and the width of the house is 20', so there is no space for water to drain, other than the 4" pipe under the house. Rain water from the roof (20'x65') already travels into the 4" pipe, in addition to the sewage from the house (original design of the house), you can see the downspout on the right edge of the picture.
I didn't want additional runoff from the patio going to this pipe, for fear that the pipe wouldn't be able to handle the water, or in the case of a clog, my basement will flood.
SO- the patio slopes inwards, and the center of the patio has a drywell. (additionally, you can get fines from the city for sloping the concrete outwards, into the neighbor's yards).
It can rain for 24 hours straight, and the water will percolate into the drywell and down through the soil just fine. BUT in INTENSE rainfalls (ONLY in august/september here in NY), sometimes 10 min. of an intense rain can produce more water than the ground can take, and the drywell will flood resulting in a pool of water on the patio. Only problem is, this water has no where to go, and goes down the staircase. At the bottom of the staircase, there is a 3" pvc drain connected to the 4" main in the house, but also during intense rain, that 3" can only take so much water. Additionally, 1 or 2 leaves will cover a portion of the drain, and seriously reduce the flow of water, which will then back up at the bottom of the staircase, and enter the basement.
I've been lucky, only having it flood 2-3 times, and less than 100 gallons of water each time, but the way things are going these days, I want to be ready for the next big storm which will surely come one day.
I dug another drywell on the edge of the patio, thinking I'd cut a strip of the concrete out, run 2 or 3" pvc from the original drywell to the new, so the water will percolate in that drywell also, but when the ground gets saturated, I notice that the new drywell is also full of water, even though I didn't even cut this concrete and run the PVC yet.
So, my new idea, please tell me if it will work: I was thinking to put a bucket with holes in the new drywell, with a pump inside. When the water rises in that drywell, pump will switch on, and throw the water into a straight run of pvc through the basement all the way to the front of the house and into the front yard, where everything is sloped properly. Any thoughts on if this will work or not? What size pump should I be looking at?
Second question: I don't need this pump to operate in the winter, because I never have a drainage problem in the winter. Can I simply shut off the pump and leave it there? or will the freeze/thaw cycle mess up the pump, would I physically have to remove it and bring it inside?
On another note, in the meantime, I bought a rubber "restaurant" mat, which has many holes in it, to put at the base of the staircase over the drain. I was hoping this would stop the spiraling of water when the flow is high, since the spiraling is what brings the leaves to the center, and clog the drain. It has hardly rained a drop since then, so I wouldn't even be able to tell if this helped or not....