French drain/crawl space question...

Captain Starbuck · 03-05-2006, 09:10 AM

I've got the lowest lot on the block and the crawl space will flood after a few days of heavy rain. I have a sump pump which works fine, but the drainage getting the water to the pump isn't the best. I was told I should dig a shallow trench from one end of my crawl space all the way to my pump. Does anyone know what the dimensions of the trench should be?

Also, I have a bunch of 'red rock' volcanic style decorative gravel in parts of the yard. I was looking to get rid of it and figured with the porous nature of the rock, it would make a great filler for the trench. That way, I could kill two birds with one stone. Would this work?

Thank you

Jettin' Fool · 03-05-2006, 09:45 AM

I would have the French drain OUTSIDE your foundation running AWAY from your house. Better to keep your crawl space dry in the first place.

JF

Captain Starbuck · 03-06-2006, 05:06 AM

Thanks for the reply. Would the volcanic red rock work for this? I may get stuck digging one in the crawl space anyhow, just because that once the water gets to the foundation, there's no where to drain it off to. Poor design on the builders part. Due to the slight slope towards the house where it then levels off, the lot must have a pump to get the water anywhere. The pump pumps it to the drain in the street.

I think I understand your comment on digging outside the foundation, it's just that the water will still settle back to the house, go under the foundation and I've got an instant artesian well.

Thanks again.

fishncliff · 03-06-2006, 06:18 AM

The rock will work.
You should check the slope of the yard and dig a trench toward a downhill slope or into a french drain area that is flat and away from the foundation.

Jsail · 03-06-2006, 07:00 AM

Dig the trenches so they flow toward the lowest point. The depth will be determined by the grade under the house. They really only need to be a few inches deep if that will create a steady fall toward the pump. You may have to dig fingers like a septic drain field; 1 main trench with fingers running to it.
The pump should be at least a foot deep. The discharge should go into your storm drain (where the cutters drain to).
The problem is that the water table is rising. If you dump the water back into the yard, most of it will re-join the rising water table.
Cut the bottom out of a 5 gallon bucket. Dig a hole deep enough for the bucket to sit in. Place a couple bricks or rocks at the bottom and set your pump on them. Run a pipe under the foundation or through the foundation vent. To get it into the storm drain add a Y just below where the down spout joins the gutter drain.
As for the rock; I'd let the water flow as best as possible, rather than soaking into the gravel. If you remove plastic to dig the trenches, replace it.