Originally Posted by mdvaden
Just had a chance to revamp a drainage problem this month. This one was unique, in that the prior "French drain" was installed about 1 year earlier.
Important things to keep in mind:
1. Never cover a French drain with sod or clay-like soil. That caps-off the drain line right away.
2. Routing perforated drain pipe or pipe with holes in front of trees, without using a barrier, invites roots to clog the system prematurely.
3. If the greatest source of excess water is the concrete patio, don't skip a drain line next to it.
We get about 37 inches of rain per year. So if the lawn was already getting 37 inches or rain, a patio means 74 inches of rain that the lawn has to (or can't) deal with. To omit that one drain line, means half a swimming pool's worth of rain allowed to cause problems.
The photo attached shows how the tree roots, in roughly a year, passed from the soil, through fabric in the trench, through the rock, through the pipe wall, and across the air space in the pipe: branching into a small wad of roots that would have continued to expand.
This scenerio is related to why 90% of the time, I do not do free drainage estimates, but schedule paid one-hour consultations to take a close look at the property and whether next door properties are part of the equation.
This is what one tree root does in 10 years time in perf. pipe