French Drain roller coaster
We have water up and over the slab in the back of the house during heavy rains. I just had a french drain system installed. They used 4" corrugated black pipe with catch basins to pvc pipe out to the street in front of the house.
After the work was complete I stuck a hose in the highest catch basin. No water came down and out the next basin 20 feet away. I then dumped 20 gallons of water through and still nothing. Finally, 2 buckets later water came through. I stuck the hose in the 2nd basin and It took 20 minutes for the water to get to the street. I dug up the backfill and with my level saw that it is running uphill considerably. I dug in the front yard where the pvc pipe was put down and found that it too was uphill.
A called a professional who came out and took measurements with his transit. He said that the whole system was like a roller coaster... up and down.
I called the contractor who assured me that everything was fine and in working order as long as the output at the street was lower than the last and highest basin. Furthermore, the french drain was releasing water into the yard and that if the water was heavy enough pressure would force it through the system and out to the street.
I thought that the whole thing should be downhill?