Replies

1. 
   Jon_R | May 27, 2019 12:24pm | #1

   Fabric wrapped around gravel will provide way more surface area than a sock over the pipe. But clay will go through any available fabric - so make sure it is easy to clean the drains. And/or use 3-6" of very fine sand as a pre-filter.

2. Expert Member
   MALCOLM TAYLOR | May 27, 2019 01:35pm | #2

   Joe,

   Flexible drain pipes, (often called Big O) has been supplanted by rigid perforated PVC pipe almost everywhere for a few reasons.

   - With Big O It is hard to maintain a consistent slope, and the pipe can have low points. Both of which make it more difficult to remove standing water.
   - Big O typically relies on twist joints - which in practice rely on the surrounding material to keep the pipe together. That means there is a much higher likelihood of the joints opening, especially if the pipes require mechanical cleaning.

   The only argument I've heard for favouring flexible pipe is cost.

3. 
   joenorm | May 27, 2019 03:34pm | #3

   Thanks,

   In a footing drain, it is my understanding there would be no slope. Is this correct? How do you orient the holes in the rigid pipe? I have read they should face down toward the soil.

   I am going to do my best to grade the site so water will not make it to the footer at all, but in the case that it does, I'de like this drain to be functional.

   Thanks

1. Expert Member
   MALCOLM TAYLOR | May 27, 2019 03:44pm | #4

   Footing drains benefit from a slight slope. They can function fine if they are flat, but flat means flat - with no portion having a negative slope - which is hard to accomplish. What they don't do well with is dips where water and sediment can settle.

   Perforated footing pipes have two rows of holes about 1/3 of the way round the circumference apart. The pipe should be placed so the shorter solid portion in between the rows faces down.

4. 
   joenorm | May 27, 2019 04:12pm | #5

   Will the footer/soil intersection act as a wall where water will hit, then rise up, hopefully making its way into the drain?

   I am wondering how you would slope a drain pipe like this over any distance? Seems like if you're above the footer at all this pipe will not do its job, but digging it below would be quite labor intensive

1. Expert Member
   MALCOLM TAYLOR | May 27, 2019 06:20pm | #6

   Very few excavations are completely flat. Make sure your solid drain leading to the storm sewer or daylight is located at the low point - or have several if necessary.

   We aren't talking about the 1/4" per ft you want on the solid pipe. Just enough to ensure no part of the perforated drain ends up sloping the wrong way.

1. 
   joenorm | May 27, 2019 06:51pm | #7

   Well, my excavation was within an inch of perfectly flat. And the uphill side of the house has to drain to daylight on the opposite side. Seems like a tall order. I suppose I could daylight in two more locations

   I think the most effective drain will be the curtain drain I plan to install as a first line of defense. This will slope to daylight in two places, hopefully taking care of 95% of the water.

1. Expert Member
   MALCOLM TAYLOR | May 27, 2019 06:54pm | #8

   "my excavation was within an inch of perfectly flat"

   Don't worry about a thing. The drains will be fine.

1. 
   joenorm | May 27, 2019 08:03pm | #9

   Not sure what you mean by this?

   thanks

2. Expert Member
   MALCOLM TAYLOR | May 27, 2019 09:21pm | #10

   As I said in post #4, a slight slope may be desirable, but flat is fine. If your excavation is within an inch (hats off to your contractor), just lay the pipes following the grade that is there.

5. 
   Peter Yost | May 28, 2019 01:14pm | #11

   One insurance policy for eventual or maybe inevitable clogging is to install a clean-out for your foundation perimeter drainage system.

   See this previous Q&A string: https://www.greenbuildingadvisor.com/question/foundation-drain-tile-and-filter-fabric.

   Peter

6. 
   RMaglad | May 28, 2019 01:46pm | #12

   use a good drainage membrane on the outside of your foundation wall (delta Ms or Platon etc), it should contour over the footing. Lay down an 6' wide roll of filter fabric butting against the footing, and laid flat away from the wall onto the excavation/side slope, socked perforated subdrain around perimeter and plumb to daylight/sewer, or worst case sump pit. Use a stone slinger to place a bit of clear stone onto pipe, slowly lift the subdrain/weeper so that there is 1-2" of stone beneath, ensure it is flat around the foundation, or better yet provide some slope, it is ok if the pipe does not have clear stone beneath it.

   cover pipe with 12" of clear stone , and clear stone 12" up onto footing, overtop of the foundation drain board (delta ms or platon). Cover the clear stone in filter fabric geotextile. backfile. Enjoy a dry basement.

1. 
   joenorm | May 30, 2019 12:59am | #13

   a drawing of this would be great

7. 
   730d | May 30, 2019 08:11am | #14

   Majority of time the drain pipe never even gets wet.
   The water collects and travels through the rock to daylight or sump.
   If money is no object than by all means use rigid pipe. I think the time and money of rigid pipe is better spent on more rock and filter fabric. We are better of with well designed and installed flexible pipe than rigid poorly installed rigid.

1. Expert Member
   MALCOLM TAYLOR | May 30, 2019 11:25am | #15

   "We are better of with well designed and installed flexible pipe than rigid poorly installed rigid."

   Sure, but those aren't the only two choices. A properly installed perimeter drain using rigid pvc is the code minimum acceptable here. What to aim at is doing the job properly.