Replies

1. 
   stonebm | Oct 08, 2003 08:21pm | #1

   The stone size will depend partly on the pipe perforation size.  If the stone size is too small, it will fall through the perforations (obviously not desireable).  If the stone size is too large, there are structural problems for the pipe.  Pea stone may be OK if the pipe is kerfed (i.e., has slits, not holes), but for holes, I'd try to find something with stone sizes of 1/2" to 1 1/2".  Contrary to popular belief, the smallest stone size does not have to be larger than the perforation size.  Stone will "bridge" across the openings to some degree so you would be OK if you had stone ranging from 1/2" to 1 1/2" and perforations of slightly larger than 1/2".  Honestly, your best bet would be to call the manufacturer- they've probably tried different sizes of stone and could give you a solid recommendation.

   Edit: One other thought- try your local quarry to see what's readily available in stone material and go from there.

   There have been similar discussions recently on exterior perimeter drains.  Try looking back to see if you can find it.  We discussed the use of "sock" pipe (pipe wrapped with geotextile).  I personally wouldn't use that product for fear of clogging of the the geotextile.  Treat your interior drain the same way as an exterior- lay down geotextile, lay in the pipe, backfill with stone, and wrap the textile over the stone to create a "burrito".  It's tried and true for systems that are a lot more demanding than house construction.

   Technically speaking, all common perforated pipes (PVC and HDPE) are classified as "flexible".  I'm assuming you're comparing the HDPE coil pipe against the more rigid 10' lengths of HDPE pipe or PVC pipe.  I'd recommend not using coil pipe due to the potential of bellies forming along the length of the pipe.  The PVC pipe could work but PVC is more brittle than HDPE and could fracture more easily if a sharp rock were up against it.  I'd suggest the 10' lengths of HDPE pipe for perimeter drains.  If you really want the cadillac (and why not considering the importance of the drain and the fact that it will be buried below concrete and not easily accessible for repairs), you could use a corrugated HDPE pipe with a smooth interior such as ADS N-12.

   Good luck.

   
   

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   Edited 10/8/2003 1:25:42 PM ET by stonebm

1. 
   astrozam | Oct 09, 2003 12:13am | #2

   stonebm, Thanks for all the info & tips, much appreciated

2. 
   Dinosaur | Oct 09, 2003 04:41am | #3

   I use ¾ Net (washed) for all my installations. But I lay in more gravel than most contractors, cover that with geotex, brown paper, or straw, depending on budget and availability. Then I put as much ordinary concrete-grade sand as I can before another layer of textile/paper/straw, and finally the landscaping soil up to desired grade.

   I also use the pleated,  sock-covered pipe without worrying about bellies or clogging: 1. a belly will only hold a small amount of water for a short while (it will drain back out through the slits if the ground water content is lower than the pipe content); and 2) since clean sand and gravel don't contain particles small enough to clog the 'sock', you only have to worry about the organic matter in the landscaping fill above, and that's being filtered through 2 layers of cloth/paper/straw plus a good three to four feet of sand before it ever gets to the gravel and finally to the sock. Its the cofferdam principle: If the first filter catches 50% of what hits it, and the second catches 50% of what's left, and the third catches 50% of what's left from that, you're already down to 12.5% before you ever hit the sock. And in practice, each layer of filtering catches a good bit more than 50% of what it receives, so your final figure at the sock is a good bit lower.

   Advantages to the flexible pipe are resistance to damage from careless backfilling and ease of installation.

   The main line of attack for an interior French drain remains a good way out for the water that gets in. I usually place one 6" BNQ through the footing for each 15 linear feet of footing on the downhill side of the house to evacuate water that comes in past the uphill footings. If the entire foundation is sitting on bedrock, I'll double that, and fill with at least 12-18 inches of ¾" gravel before pouring the slab. Cover the entry to the through-footing BNQ with two layers of ¼" wire mesh strapped in place with SS hose clamps (to keep the gravel under the house) before you shoot it in.

   Dinosaur

   'Y-a-tu de la justice dans ce maudit monde?

1. 
   caseyr | Oct 09, 2003 07:54am | #4

   With the interior drain pipe system, how do you handle going under the foundation to get to daylight (where that is feasible) - particularly if the foundation is fairly deep (I only have to go down 24", though).  Or do you put a sleeve through the foundation wall and run the pipe through that? 

1. 
   Dinosaur | Oct 09, 2003 08:38am | #5

   Ideally, you set the plugged BNQ into the form for the footing when it is poured, then unplug it when the forms are stripped. In a retrofit, you need to rent a Kango and bang your way through. This is noisy, dusty, and physically hard on the bod, but....

   If you go through the foundation wall above the footing, water inside the perimeter won't start to evacuate until it rises above the floor slab, which is probably what you're trying to avoid. And you'd still need to rent that Kango....

   Another solution is to dig a sump inside the basment, install a submergible sump pump and dump your drains into that. You can run the discharge from this out through a 2" pipe to the municipal sewer if your municipality allows that, but DON'T run it to your own septic system; septic system life is determined in large part by the total through-put of the system and if you add ground water to the system, you will shorten its useful life by many years. In this case, dig a rock pit outside the basement (down grade from the house, of course) and dump the two-inicher into that. Or if you can, just run it to daylight and let it run off on the surface.

   Make sure both the sump and the pump capacities are large enough to handle the volume of water you'll be dealing with.

   Don't neglect to install a one-way flow valve on any line you connect to the municipal sewer system.

   Dinosaur

   'Y-a-tu de la justice dans ce maudit monde?

   Edited 10/9/2003 1:41:12 AM ET by Dinosaur