what to do if landscape drains can't be sloped?
Two sides of our home have absolutely no drainage, and during a heavy rainstorm the water collects about 4" deep against the house. So we've hired a contractor to install gutters and floor drains in the concrete around the back of our home. They removed the concrete walkway that used to get flooded, and placed PVC drain pipes leading around the house to the driveway.
The problem is, the pipes cannot be sloped with a proper 1-2% incline. There is one area of the pipe that goes through an area with other electrical lines, and the trench cannot be dug any deeper. And GC says he can't raise the other end or the drain will be higher than the floor. So portions of the run are sloped downhill, and others are either flat or even very slightly uphill.
My question is how much of a problem will this be? The contractor ran my hose into the drain and showed me that it exits the drains at my driveway. But when he turns the hose off, there's a significant residual--probably several gallons of water that are left in the pipes. Will this cause problems with mosquitos, mold, etc?