French Drains in Cold Climates
French Drains in Cold Climates
(OP)
I have a concern that my newly installed french drain will get damaged by winter thaw and freeze cycles. My house downspouts are connected to a French drain and I've got concerns that the snow/ice in the gutters will cause problems in the French drain during winter. I live in SE Michigan. Do I need to be concerned?
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
Can you see the outlet point of the drain? This is where you will probably have the most maintenance, but is better than having it buried.
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
Following are my 'standard' recommendations (Colorado Foothills to Mountains) which may be appropriate to your original post:
... However, it should be noted that there is a considerable potential for seepage water on this site, particularly during wetter (snowmelt) seasons. Seepage can be expected to flow along the surface of the formational materials and in the fissures in the formational shale. It can also be expected in the upper colluvium in wet seasons. Seepage could be severe enough to present problems in construction, if construction is undertaken during wetter seasons. As a result of the seepage potential on this site, a subsurface peripheral drain system must be used for the structure. In is possible that two (2) levels of subsurface drains may be required. An upper, shallow drain may be required to protect against snow melt and poor surface drainage and a deeper drain at the foundation level to protect against deeper subsurface waters.
At the higher altitudes of this site, difficulty with freezing of drainage lines at the discharge point is probable. We recommend that this be overcome by discharging into a protected, coarse rock and cobble fill or mound. As an alternative, heat tapes can be used on the discharge point of the pipe. The drain outlet must also be located with due consideration given to the proposed pattern of snow storage and removal. Careful consideration must be given to snow plowing, plowed snow stockpiling and snow which will fall off/shoveled off the roofs (especially the northerly sides of the structure)as to preventing proper drainage of runoff away from the foundations areas, during the winter and the spring months.
RE: French Drains in Cold Climates
Ideally, the cheap flexible pipe (solid or perforated) is avoided because of places for dirt to accumulate and bellys cut the flow rate and capacity.
Every place has different minimum temperatures and timing of the cycles. I have seen ground frozen down only 6" with 18" of snow, but after a month of daily lows of -15F or much lower (-52F).
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
- The "French" drain would be between 4-12 inches deep
- my downspouts would not be connected to the foundation drain - I want my downspouts connected to the French drain, totally separate from the foundation system. The whole point is to get water away from my foundation. It would be 4" OD black, 'plastic', flexible, perforated hose with a sock over it. It's sold at the big box stores. The end of the hose would dead-end in the ground. About 600 SqFt of roof would be diverted into this French drain hose.
- I plan to put 'leave guards' on the gutters where the flow is coming from
RE: French Drains in Cold Climates
assuming 2 inches of rain will produce 100 cubic ft of water runoff from the roof. you need to store all of that or more depending on your desired design storm. do not use perf pipe close to the house
RE: French Drains in Cold Climates
Bury the french drain as deep as possible. You will have freezing problems if only 4"-12" deep, unless your underground pipe grade is very steep.
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
I hope I am not interpreting incorrectly, but are you planning to take your roof water and run it into a 4" perforated black pipe with a sock on it? Then are hoping to have that water exfiltrate from the pipe into a trench filed with coarse rock (your French drain)? If so, it is an upside down design and would be a form of "dry well" in my area, but made wrong. The sock would trap a lot of stuff and eventually plug and then nothing would work.
Leaf guards are not perfect and let a lot of stuff thru and even plug themselves in some cases..
Clarify if I am wrong.
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
As I said previously, I highly recommend you bury this pipe deeper. And agree with cvg that you need bigger/longer pipe.
RE: French Drains in Cold Climates
Ok, it will be a dry well. Forget the words French Drain. Agree, use perforated pipe. However, that sock is not needed, costs mre and is likely to plug. Water runs out and doesn't run in. It is water flow that carries along dirt and the direction is out.
The main info you need to provide is what type of soil is this going into? If it is clay soil, it may not work well or at all. This design should be the same as one would have for disposing of sewage water from a septic tank. If you really want it to work and need to figure sizes of dry well, check with a local Soil Tester, Sanitarian or similar profession who size waste water drain fields.
A crude way to figure size is to run an old fashioned infiltration test and do some calculations. Dig a hole to the depth you want (and the shallow depth you show looks not enuff) and set a ring, say a 5 gallon pail with the bottom cut out. Fill water inside it and outside it to same level always. (outside so your inside infiltration is only down, not sideways). Fill maybe 8 or 10 inches high. Let it soak for a few hours and keep inside and outside filled. Then (assuming a steady state), measure the drop in inches per hour. That can be done with a pointed measuring stick, against a board across the top. Then, that is a rough estimate of how well the dry well will work on a cubic foot per square foot of area for a given period of time, say one day. You might assume a rainfall of 3 or 4 inches per day for the extreme. An hourly rainfall of one inch could be used to figure volume of trench needed as a minimum. Don't forget the stone will take up maybe 65 percent or more of the total volume. To cut down on the length of trench, just make it wider. Play it safe and daylight the end of the pipe, even it it is up. Put a screen there to keep animals out.
However, keep in mind about freeing of ground. If the surface is not snow covered, frost depth can go well below 4 feet down in sand and gravel and a few feet in fat clay. If water table is close to surface, then this dry well method won't work very well.
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
RE: French Drains in Cold Climates
The freezing issues I've witnessed occurring at the outlet are for drainage systems that are properly buried (usually at least 4' deep). I still think you are going to have freezing issues further up the pipe if you only bury it a few inches deep.