I thought I knew what a french drain was until I came here, where there seem to be different definitions. Therefore, I can't say I know what you are creating and how you are doing it. You might want to sketch a cross section view and plan of the project, and explain the details ... the complete thing.

Big box home improvement stores have prefab French drains in ten foot sections for fifty bux. They are the black plastic drainage piping surrounded with pellets enclosed in a sleeve you sink into a trench, cap the end, and you can extend more piping with a joint connector to run the water away from the area that trickles through to the carrier pipe. There are more expensive designs a contractor can do for thousands of dollars. We have a middle range drain that runs along the front of our garage that fills a carrier basin that spills over into plastic drain pipes that run down hill along the side of the garage to the road below the house. I have to clean the basin out twice a year. The neighbor next door has a higher end French drain behind her house and along her garage that is accessible by grates over the top. Hers cost much more than ours. We are in the hills and the water comes down and around. The other side of our house has a flume fed by a drain and gravity carries the water down hill and under a sidewalk into a drainpipe to the sewer line.