French Drain - River Rock or Crushed Stone

[MMH]

I am putting in some french drains. I was planning to cut a ditch that is 12" wide and 3 feet deep, drop a 4" solid (non-corrugated PVC or HDPE) perforated pipe. I was going to fill with 2" to 3" crushed limestone. This is just regular non-washed aggregate. One of my friends suggested that I use river rock instead saying that it ill let the water flow thru it better & that the aggregate will silt up. Cost is an issue. I can get crushed stone for $14 per ton vs. $32 per ton for the river rock. I'm inclined to go w/ the crushed stone but thought that I would post the question here first to make sure I'm not making a mistake.

[TCJatko]

Be sure to use one of those sleeves that goes over the pipe to keep out the silt.

[MarkV]

Was it a typo when you said "fill with 2" to 3" crushed limestone." That amount of stone will not even cover the pipe. I think you will need much more than that.

MarkV

[MMH]

Was it a typo when you said "fill with 2" to 3" crushed limestone." That amount of stone will not even cover the pipe. I think you will need much more than that.

MarkV

2" to 3" is the size of the stone (it is called b3 in this area). I plan on filling the entire trench with stone.

[MMH]

Be sure to use one of those sleeves that goes over the pipe to keep out the silt.

Good Idea - Thanks.

[vtsnowedin]

Crushed stone will work as well as river rock as long as it is screened to one size so that all the sand and stone dust has been removed. A couple of inches under the pipe and back fill to at least a foot above the pipe with the stone then switch to clean sand up to your topsoil elevation if your crossing a lawn or up to the road base if your in a driveway. 3/4" crushed rock works well for this.

[jomar215]

Crushed stone will work as well as river rock as long as it is screened to one size so that all the sand and stone dust has been removed. A couple of inches under the pipe and back fill to at least a foot above the pipe with the stone then switch to clean sand up to your topsoil elevation if your crossing a lawn or up to the road base if your in a driveway. 3/4" crushed rock works well for this.

+1 on the screened stone. You don't want any silt in the mix, or it will plug your pipe. +1 on the sand, too. It's an added expense, but it's worth it if your dealing with a lot of water. I might add a layer of hay (about 3 inches thick) above the stone, before the sand. You could use landscape fabric, but it's more expensive. This will also help reduce the amount of sediment working its way down to plug your pipe.

Are you taking it to daylight? What's the application?

[Hill-Billy]

MMH, yes your way will work fine without river rock. Sleeve the pipe. I've done this many times for many years and it works fine. I use regular (non-washed) 1-1/4" rock because it's alot cheaper than 3/4 around my parts. I used the PVC pipe with holes in 1/2 of the pipe, holes facing down in trench. I also have used the corrigated pipe. I've seen no difference in either, except it's harder to get the sleeve on the corrigated pipe. If you go that route, buy the corrigated pipe with the sleeve already installed. I have no more water issues. As for the sand, never heard of doing that. Why would you pay for screened (washed) rock to remove the sand and then dump sand ontop of the rock? Guess that's why us New Englander's really are the best craftsmen!

[reggiejr]

We use 3/4" (non washed)crushed rock mostly around here with most of our drainage projects .
Imo 3" rock would be pretty course around such a small light duty pipe.I would recommend bedding with 3/4" rock then you could top off with the heavier aggregate.
We always use drain field fabric with our under drains and it works well if your concerned about silt. We usually roll it out over the rock before topping off with back fill material.
The pipe we use mostly is highway grade ads n-12 smooth bore perforated pipe in 20' sticks.Its good strong pipe and its very easy to work with.
Course clean sand is also an option.

[vtsnowedin]

Actually I've had a crew put in a couple of miles of under-drain this year that is just back filled with clean coarse sand. Sand varies from deposit to deposit from the velocity of the water that placed it there. No need to wash it if the glacial river that placed it has already washed it for you. The sand we are using has just 2% silt passing a number 200 screen. A 200 screen has .003 inch openings. This sand is coarse enough to not go though the openings in the six inch corrugated plastic pipe and clean enough to let water perk down though it to the pipe and then out. Crushed stone around the pipe is a step up as it does the same job as the sock and keeps any fill material from entering the pipes perforations and is a good bet if you don't have the means to test the sand.