[molson]

hi everybody,

we have a client that lives near the mississippi river and has a suspected underground creek or stream under or near their house. they have a sump pump in their basement that at it's height in the spring pumps out 2 gallons of water every 2 minutes. it's at it's worst for about 2 months in the spring after the snow melts.

we are hoping to install a 3'x3'x3' french drain about 15 ft away from the house. we'll use PVC pipe to get the water from the house to the drain.

when i say french drain what i mean is: a PVC pipe that leads to a perforated rubbermade box filled with rock and surrounded by gravel and then sand.

we've never done this before though so i have a couple concerns:

1. is installing the pipes and french drain as easy and simple as it sounds?

2. the pump runs in the winter sometimes. what might happen if the french drain area froze up? we're in minnesota.

3. have any of you delt with a similar situation before?

4. is there any calculation for gallons per minute to establish the size of the drain area? our 3'x3'x3' is just a guess. does that sound ok?

as always, thanks so much in advance for any insights. other than this component of the job the rest is really great stuff so we want to make sure we nail this part!

cheers,
molson

[yes.itsconcrete]

done some in nj ( 5 yrs ) where we had 12" - 24" frost

ok, here we go,,, 1 gal = 231 cubic inches,,, 30 cycles per min @ 2 gal ea = 8.02 cu ft,,, in 24 hrs, 193 cu ft,,, sounds like a 35-40 gal sump from apron store,,, & right now this pump drains out on the lawn ??? when snow melts, is frost still present & til when ?,,, unless you have gravity flow of discharged water, this isn't the good recycling you want to witness original water source could be underground stream, surface water infiltration, or just hydrostatic.

a true french drain's a swale on the surface ( originated at fountainbleu, fr ),,, what you describe is a 27 cu ft cistern depending on soil percolation for efficiency & size,,, your box of rocks will hold more water if it ain't filled w/rocks,,, discharge this drain system down near the storm sewer inlet w/4" s & d pvc pipe,,, 1/4" drop in 10' won't ice up,,, to address your concerns: 1, yes - just dig hole & install 4" pvc; 2, how could that happen since its all below frost line ???; 3, done some 4, nfw not for the amount of wtr you could have.

worst case scenario figuring you'd have no perc quality in the soil, this system pumps 1,440gal in 24hrs - that's 1537.33 cu ft,,, if running at your posted rate so you'd need a box measuring 10' x 20' x 7.685' ( no rocks, neither ) we ran into jobs where there was no slope to the storm drain - that meant digging & discharging below grade - you may have to have a permit - we didn't.

hope this isn't too confusing & helps ( yic-yac )

[RHPL]

I have dealt with a similar situation with a house that is only a couple hundred feet from a good sized river. in this cituation we had the sump pump connected to 4" solid PVC out side of the house and run it about 40' away from the house with a pop-up emmiter on the end (a product from a company called NDS). This takes care of anytime the ground isn't frozen. In the late fall this is simply disconnected at the house and the water from the sump just shoots oput the side of the basement wall 4 of 5' from the house. I'm near Toronto and we get at least 2 feet of frost. I'm not worried where the water goes in the winter since it is all frozen up anyways (just make sure the property has at least some slope away from the house.

Otherwise if you want a system that will work all year round then you need to have the sump exit the house at least 2' down (I'd go 3' or 4' to be safe and run the water in 4" PVC at least 20' from the house (the further the better) and then install a cistern. This would be a very involved installation (almost like installing a septic system) but should do the trick.

[Pelican]

I don't like plumbing drainage in to any kind of perc system. In most cases the reason there is water in the basement is because the ground is saturated. You run the risk of your curtain drain or dry well being saturated and unable to handle the water you are sending to it.

Unless your grade prohibits it, daylighting your drain pipe is a much safer method.