A contractor installed a french drain to divert water from my back yard out to the street in front of the house. I tested the system and it takes 20 minutes for the water (from a hose) to go from the farthest basin to the street. I called an engineer friend to check the slope. He says that the whole system runs up and down. Shouldn't the whole thing be entirely downhill to the street? The contractor says that it's okay to go up and down just as long as the exit point is lower than the highest basin. Water from a heavy rain would push itself out. Is this acceptable? Or, should I insist that the system be taken out and reinstalled?
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If it doesn't slope down then it'll leave points for water to collect. This generally is a bad plan. Why are some areas of the pipe lower? Is there a surface issue that requires it? As in, the lawn slopes down and they needed to put the pipes a certain distance down. Or utilities?
Contractor sounds like he's full of it. The only way that variances of elevation could not impact proper drainage is if the system was sealed, primed, and then drained, so that the water pulled a siphon when exiting to daylight.. which is pretty much impossible in a drainage system like this.
Sure, it will drain eventually when enough water enters the system.. but it certainly isn't ideal.. and not the proper way to install a drainage system. I'd have the contractor fix it. (Assuming, of course, that it wasn't absolutely necessary to do it this way. I guess it's possible that this was the only option, but seems unlikely.. seems like this was the 'easy' option).
Last edited by NegativeTen; 07-12-2013 at 04:10 PM.