What is the appropriate French Drain depth in PA ?

Submitted by Dredly t3_10ueh87 in Pennsylvania

I'm going to be installing some french drain around my yard in the spring to stop standing water and give my gutters a proper place to drain out into, but the frost line in PA is like 4'.

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(disclaimer) its 30+ feet away from my foundation, no underground lines in the area, no HOA or anything, and the only way any of this water could impact a neighbor or a road way would be if the world is already flooded as I'm the last house at the bottom of the hill and there is a stream running through the bottom of the valley 150 yards+ from where I would be doing the work.

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Anyone know how deep I should be looking to go with the drain, and any issue using hardwall PVC instead of the black corrugated pipe with regards to damage / breaks from the winter?

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bluezinharp t1_j7bc23v wrote

If you're the last house at the bottom of a hill, you might be fighting a losing battle.

One would have to see the slope, grade, location of the stream, roads, out buildings, and perhaps a few photos to give an accurate assessment.

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Dredly OP t1_j7bcido wrote

I'm mostly attempting to divert water way from flowing across my patio and driveway and around my yard. I'm hopeful it will work to just catch and divert the surface water... I just have no idea how deep I should be looking to bury the pipe to keep it from being damaged by the winter

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NerdyRedneck45 t1_j7c70ci wrote

Hot take, but frost lines from decades ago are such BS now. The coldest regions of the state barely freeze down a few inches anymore except during the craziest winters. Go however deep you can while keeping a good slope. Definitely at least 18” but otherwise you’ll be fine.

Side note though, it’s hard to keep those things from clogging. And they’re expensive. If you can possibly swing it, just dig a shallow swale/ditch.

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Dirt_dawg21 t1_j7cigtk wrote

Agree.. a swale would be your best option. If you're going to run pipe, use black perforated with the silt fabric sock on it and put it in a 2b stone bed.

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Successful-Land8681 t1_j7d7i04 wrote

Frost lines are not related to drainage. They are only a concern with footing depth for buildings where freeze thaw can cause damage and heave to the soil supporting the structure.

PVC gets brittle and will break then collapse blocking your efforts in only a matter of a few years. Use the black pipe, it should be HDPE.

Bottom of hill comments = runoff to me. French drain won’t work as the water needs to absorb to get to the drain. Swale your yard and give the water some where to go.

Last resort would be to create dry diversion beds out of decorative landscaping rock. You have to line the trenches with landscaping fabric. Never use woven fabric, water does not pass it well, use the punctured fabric.

Sorry for the diatribe, I’m a civil engineer/ nerd.

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Dredly OP t1_j7dfdff wrote

I was worried about the water freezing in the pipe causing it to freeze / expand / crack but I may be over thinking that problem.

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It is all run off down the mountain, as well as water from my gutter discharge. I'm at the bottom of approx a 1mile long slope however there are multiple areas that are flat-ish along the way so I'm not getting the entire hills worth of water in my yard / across my driveway and patio.

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I can put a Swale in, but in order get the water to go with the slope, and clear my driveway and outbuilding, It would have to be 50+ yards up away from my house, and wouldn't catch all the water

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Successful-Land8681 t1_j7e2sxf wrote

You could did a couple dry wells (stone pits below ground wrapped in geotextile). You can run your gutters to them and then give them a drain pipe further away if you want.

French drain will work too if you have somewhere to discharge it.

Either way I think you are going down the correct path.

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Dredly OP t1_j7ec8kv wrote

My ultimate 2 problems are 1. my backyard and side yard just basically is unusable for a day or 2 after rain because of the water and 2. massive runoff is eroding the edges of my driveway, causing it to crack and I REALLY don't want to replace it if I can avoid it...

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only thing I can think of is to divert the water around the 2 problem areas... but I can't go the "easy" path as its fully blocked by my driveway (it has a "T" section that goes to a separate garage, so its not as simple as just run a drain along it

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