Drywell Questions And Design Review

[ChaseGizmo]

I have to build a drywell to try to get some of the run off from the gutters into the ground before the water goes to the drainage ditch. The drainage ditch is the farthers from the water pond so it is almost level with the bottom on the yard.

This is the deesign I am thinking about using but suggestions or corrections would be appreciated.

The gutters will each feed into a solid pipe which connects to a perfereated pipe 10 feet away which will continue for 50 feet and then enter a NDS perferated flow-well perferated pipe will exit the flow-well and then continue 20feet to a dry well. I plan on putting pop-up emitters on the flo-well in case the dry well should get full to protect the water from coming back up the line.

Questions;
What is the best type fabric to use?
Can the rocks used be 3/4 washed gravel?
Should the pipe be 4" or 6"?

I have read that when the pipe enters the drywell it should be as long as the drywell and palced on top of the rock base and then covered with more rocks with the end of the pipe being capped off. Is this correct?


Thanks for any assistance

Chase

[suemarkp]

What is a flow-well type of pipe?

I would suggest getting farther from the house than 10' before you transition to perforated pipe -- perhaps at least 30' of non-perf pipe. Put a gravel bed around the perforated pipe to help it drain into the dirt. Use any fabric rated as a filter cloth to either line the gravel trench (top and sides before filling with gravel) or to slip over the pipe (not as good as protecting the gravel bed).

Use smooth drain rock, and the larger the better. If you get 1.5", there will still be a lot of 3/4" in it. The larger rock has more void space to hold more water. Pipe should probably be 4", as it is easier to find and much less expensive (same with the fittings).

I would run the drain pipe to the middle of the drywell hole and put a grate on the end of the pipe to keep the gravel from falling into it. You may also want to drill some extra perforation holes in the bottom of the pipe (just before the outlet grill) within that dry well. How large were you planning to make the dry well (diameter and depth)? If you have a long enough gravel filled trench, you may not need a drywell at the end (but a pop up may be good insurance). Calculate the surface area of your trench -vs- the surface area of your well. You may find the trench has more area than you were planning with the well, and you have to dig the trench anyway (just dig it wider -- a full 10" to 12").