When you first decide to owner-build, it’s easy to focus on the “fun” aesthetic choices. You get to pick your flooring! Choose the countertops! Then six months later you find yourself manufacturing custom foundation drain pipe in your parents’ garage at 1am, vaguely wondering what happened. To be honest, the farther along I’ve gotten in this project the less I’ve thought about the “fun” stuff. If push comes to shove you can always change your countertops or repaint walls. But your foundation drain? Yeah, you gotta figure that out now and you really have one good chance to get it right.
Foundation drains help drain water away from foundations. Pretty self-explanatory. Liquid water rises up into holes in the underside of the drain pipe, which runs to a pump, drainage field or to daylight. Instead of using the flimsy-feeling corrugated black pipe sold at big box stores, I decided to build my own out of rugged ABS schedule 20 rigid pipe. ABS isn’t often used for foundation drains in cold climates because it can be susceptible to frost damage, but I have a few things working for me: my foundation walls are well-insulated so the footings (and pipe) should stay warmer, and the pipe is surrounded by well-drained sewer rock covered in heavy-duty filter fabric. Using ABS also allowed me to make a daylight cleanout, so I can snake the pipe if it ever clogs. If you’re curious to hear how it works out, ask me in five or ten (or twenty) years.
Photos taken October 12-21, 2019. Posted December 16, 2019.
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As a continuation from my comment on your previous post – I am also extending the existing french drain to a side of the house it was omitted. I assume it was just cheaper to do it yourself? Could you share details on your design, ie. hole spacing and size for perforations. What type of rock, how much of it, and where did you get it from? Lastly, did you cover your pipe in burlap or some other mesh to prevent fine rocks and soil from seeping through?
Thanks
I don’t recall what the hole spacing or size were exactly. I think I did two or three rows of holes, and spaced each hole in a line a few inches apart. When the pipe is installed, the holes face down. I covered the pipe with a full truck load of sewer rock (aka “drain rock”) from Alaska Sand and Gravel, and put heavy-duty landscaping fabric over the rock and pipe before the foundation was backfilled.
Using ABS for this purpose was sort of experimental. I created a cleanout so I can inspect the system down the road and I’ll be curious to see how it holds up. In any case, the drainage at my site is really good, and Anchorage doesn’t get much annual precipitation (17″ per year). Even if the whole thing fails I’ll probably be fine. As far as I can tell, few houses in Anchorage actually have functional foundation drains.
Interesting that you made the holes face down, does that work as well? I assume you rely on hydrostatic pressure to fill up the pipes as opposed having the water trickle in.
The point is to whisk bulk water away from your footer. If there’s enough water to cause problems, it’ll upwell through holes placed downwards. Other people place the holes upwards though, and some folks even place them facing to the side. There doesn’t seem to be a lot of agreement on this question. The whole topic of French/foundation drains can get a little fuzzy, perhaps because most drains won’t be seen again after they’re put into operation. It’s hard to get a sense of what works and what doesn’t when you can’t easily assess the results of your work.
Another question – how far down did you lay the pipe?
The pipe is placed level with and a few inches away from the bottom of the footer.