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Discussion Starter #1
All, I need to set up a grid iron configuration French drain to drain a lot of standing surface water on top of my clay upper lot.

They will be approximately 200 foot runs on the laterals feeding into an approximately 300-400 ft run main.

Do the French drains need to be below the frost line which is apparently 50 inches deep here? Was going to use solid walled plastic piping with perforations on bottom

Property doesn’t need to drain if it’s frozen obviously

Have read on some sites about freeze thaw
Damaging some drain pipes

Below frost line will add significantly more trenching hours - i was already planning a 2 ft wide trench with 6 inch pipe

At lower end of the project ie lower elevation I’d probably be digging deeper than the adjacent waterfront water table
 

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I've had them 6-12" below the surface and never had a problem.When put in right and enough pitch there won't be much moisture.The stone on the sides and top take a lot of the movement of the frost.
 

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I've had them 6-12" below the surface and never had a problem.When put in right and enough pitch there won't be much moisture.The stone on the sides and top take a lot of the movement of the frost.


I have something similar but it is solid 6” pvc that is also 6-12” down and is used a a drain for our sump pumps and the eves troughs. They run all winter for the iron filter and the softener. The trench is sand filled under cedar chips and is 150’ Long. The last 20’ is under grass and ends at the ditch bank. I have roughly 1/8 - 1/4” pitch per foot and it does not freeze up in the winter. I thought the frost might heave it but in 2 winters it has not been a problem and is still where I put it.
 

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Like the others mentioned 12" to top of pipe should be fine. In traffic areas such as lawn mowers. The key is to keep all the lines drained. So depending on your contour of yard you may have part of the line 12" and other parts deeper.
I have a whole system of gutter drains and piping as well.
 

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I have a run under the eves of the pole barn and it isn't below the frost line. Mine is a 6" perforated drain tile with a fabric sock like material over it to keep the dirt out. Since it is flexible there isn't a concern about movement.
 

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All, I need to set up a grid iron configuration French drain to drain a lot of standing surface water on top of my clay upper lot.

They will be approximately 200 foot runs on the laterals feeding into an approximately 300-400 ft run main.

Do the French drains need to be below the frost line which is apparently 50 inches deep here? Was going to use solid walled plastic piping with perforations on bottom

Property doesn’t need to drain if it’s frozen obviously

Have read on some sites about freeze thaw
Damaging some drain pipes

Below frost line will add significantly more trenching hours - i was already planning a 2 ft wide trench with 6 inch pipe

At lower end of the project ie lower elevation I’d probably be digging deeper than the adjacent waterfront water table
No, drain lines do not need to be below freeze thaw depth, as water is almost continuously moving (think leaving a faucet barely running in a cold house, so the pipes don't freeze). What would concern me about depth is the susceptibility to crushing due to weight of vehicles or tractors. 1' minimum, but i'd like mine to be 2' to the top of the pipe. This is also industry standard for site design around here at least.
 

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Discussion Starter #8
Ok next debate. Big box stores don’t seem to be carrying six inch perforated pipe.

I want it to be rigid to maintain grade

Called plumbing supply store they said I would want perforations all the way around the pipe as opposed to just near the bottom of the pipe as I specified

Application is draining 1.5-2 acres of heavy clay heavily saturated rough lawn

Also looks like six inch much harder to get and much more expensive than four inch - should I stick with six inch? Is it overkill ? Will I be glad I had the extra capacity ??

Again three 200 ft laterals plugging into an approx 300 ft main in a grid iron configuration
 

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No, drain lines do not need to be below freeze thaw depth, as water is almost continuously moving (think leaving a faucet barely running in a cold house, so the pipes don't freeze). What would concern me about depth is the susceptibility to crushing due to weight of vehicles or tractors. 1' minimum, but i'd like mine to be 2' to the top of the pipe. This is also industry standard for site design around here at least.
I agree with Yukon C. as long as the water runs it will not freeze, if you have a bump in the line and water can back up you will have a problem. lots of stone, 2' wide trench, 2 feet deep, perf pipe holes down not that flexible black stuff, (i'm just not a fan of that material and never used it) silt barrier around the stone and you'll have a great french drain. Remember sub surface drains (below the frost line) are a whole other use. One more hint, make sure animals cannot build a nest in the end of the pipe if it dries up, put an end cap on the pipe with some small holes 3/8" or so drilled in it and a little stone after that... don't glue the end cap on...!!
 

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Ok next debate. Big box stores don’t seem to be carrying six inch perforated pipe.

I want it to be rigid to maintain grade

Called plumbing supply store they said I would want perforations all the way around the pipe as opposed to just near the bottom of the pipe as I specified

Application is draining 1.5-2 acres of heavy clay heavily saturated rough lawn

Also looks like six inch much harder to get and much more expensive than four inch - should I stick with six inch? Is it overkill ? Will I be glad I had the extra capacity ??

Again three 200 ft laterals plugging into an approx 300 ft main in a grid iron configuration

In my thread that I linked above, is a pic of pipe in the back of my old Outback. It is all 6" and perforated. The green/blue pipe only has holes on the bottom, it is thin walled. There were places that I knew the pipe would get driven over by vehicles heavier than a 1 series Deere, so I went to the black pipe in those areas. The black pipe is similar to the rigid black corrugated pipe that is 12" diameter and higher, what we use for driveway sluice pipes in these parts. It is made to be driven over and the holes are all around, not just on the bottom and it has a smooth inside. I felt I wanted 6" "just in case". In my thread, I noted that I did my project in 2 phases, 2 years apart. In that period, I watched the water flow. We had some heavy rains, and the 6" pipe was never even half full at peak flow times. So for phase 2, I actually reduced to 4". I have had even more heavy rains, and the flow isn't even half of the 4" at the outlet. You can move a lot of water in a 4" pipe. And, in my phase 2, I had forgotten how much more expensive the 6" pipe was, and the fittings are even worse, the 4" was much more affordable.
 

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Discussion Starter #11
In taking into consideration the recommendation to start this trench at 2 feet below grade it occurred to me that the French drain will cross perpendicular to my
Natural gas and public water trench at three points. The gas line as I recall is buried two feet below grade in sand. Specifically gas company
Didn’t want gravel near it for
Fear of puncture. I have a call into their field engineer but they’re all out on outages.

Any ideas ?
 

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In taking into consideration the recommendation to start this trench at 2 feet below grade it occurred to me that the French drain will cross perpendicular to my
Natural gas and public water trench at three points. The gas line as I recall is buried two feet below grade in sand. Specifically gas company
Didn’t want gravel near it for
Fear of puncture. I have a call into their field engineer but they’re all out on outages.

Any ideas ?
You can sleeve your gas line the width of the trench with PVC. Effective and fairly cheap.

Your water shouldn't be an issue, it'll be at least 4' deep if it was constructed per most regulations. Still, work in these areas with caution.
 

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I agree with Yukon C. as long as the water runs it will not freeze, if you have a bump in the line and water can back up you will have a problem. lots of stone, 2' wide trench, 2 feet deep, perf pipe holes down not that flexible black stuff, (i'm just not a fan of that material and never used it) silt barrier around the stone and you'll have a great french drain. Remember sub surface drains (below the frost line) are a whole other use. One more hint, make sure animals cannot build a nest in the end of the pipe if it dries up, put an end cap on the pipe with some small holes 3/8" or so drilled in it and a little stone after that... don't glue the end cap on...!!
The rodents in my area must be smart...I have never even seen them start a nest in the end of a drain line. They like warm and dry. Like any nook and cranny on our tractors. :cheers:
 

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I've had them 6-12" below the surface and never had a problem.When put in right and enough pitch there won't be much moisture.The stone on the sides and top take a lot of the movement of the frost.
X2 :thumbup1gif:
 
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