Concrete sand vs gravel in basement French drain 1

[973CHRIS]

I dug out a 14'x14' crawl space which was attached to my basement, i installed footings and block walls which I filled with concrete and rebar. I have yet to pour a floor, until this year the whole area was dry, however this year we have received a lot of rainfall in the northeast and the area gets soaked, I use a submersible pump on a daily basis to remove the water. the soil is a very heavy clay filled with rocks which makes tough digging. I'm installing a sump pit in the corner and I'm going to run a French drain around the whole perimeter of the basement to prevent any future disasters as I want to finish the beasement in the future. My house is graded lower than the street so water flows towards the house. 2 yrs ago I installed surface drains at the lowest part of the grass and a trench drain which driects the water out to the street behind my house (downhill) it still works properly. (I used gravel but have 2 clean outs)

My question is should I use corrugated pvc with slots in my basement system or schedule 20 (the green stuff) pvc with holes? And should I use a sand concrete sand backfill instead of gravel which is recommended by most basement contractors? Is a sock required with sand?Also how much of a pitch should a be installing? We currently have a sump pump on the opposite side of the basement with basin with holes drilled in it. The basement also has a floating slab which allows moisture to linger. My goal is to direct all water to the new sump pump basin and install a sump pump and a city water backup pump and close the gap between the walls and floor so the dehumidifier doesn't run half a year. I want to install a bullet proof system as I will finish the basement in the future.

Any feedback would be great, thanks

I will upload a sketch later with photos

 

[GeoPaveTraffic]

Likely to get a lot of different opinions on this one. Here is my 2 cents worth.

As for the pipe materials, ether one will work. The green solid pipe will convey a little more water but will be a little harder to install. If you can find the black corrugated pipe with a smooth inside, it gives you the best of both worlds. In either case install the pipe with the holes at the bottom.

As for backfill material, I would use concrete sand. In most cases the sand is a reasonable filter for clay soils so you will have less problem with the clay soil migrating into the backfill. No need for a filter fabric lining in the trench if you use sand. If you choose to use gravel, then you really should line the trench with needle punched filter fabric prior to backfill.

If you use sand you will need a filter fabric sock on the pipe to keep the sand from migrating into the pipe.

Best of luck.

Mike Lambert

 

[oldestguy]

I vote for GeoPaveTraffic. With gravel alone and no fabric it MAY WORK if very little flow of collected water, but why risk it. You may need more than perimeter drains, to be sure. One down the center of basement is good insurance.