I have recently purchased an older home (1970) with foundation issues. I have remediated most of the interior issues with either epoxy or urthethane injections, along with anchors. I have also installed new gutters and ran the drains 15+ feet away from the house. However, the house was built without any type of drainage system, and I am planning on excavating one wall to waterproof the exterior of the foundation wall. While performing this excavation I thought it prudent to install 4″ drain tile alongside the footing of the foundation, the issue i have is that I have no where for the water to drain (no interior sump system, and can’t run to daylight), therefore I was going to put in an exterior sump system. The footing runs about 5-6′ below grade. My questions are:
How much deeper should I dig the pit to allow for proper drainage and fill (2-3′ was my assumption filling with gravel).
If the pit is this deep (8′-9′), do I have to worry about the pit water freezing or the pumps breaking in the extreme cold temps? will a well insulated cover and the depth of the pit help these situations? (frost line has never reached below 36″ in my area)
What can be done to keep the evac pvc line out of the pit from freezing (if I am pumping straight to the surface and away from the home)? – one idea i Had was to keep the evac line below the frost line, and pump to a dry well further out into the yard? although this would require two rather large holes and a large trench?
I really appreciate any help in this matter.
The soil type is a hard clay.
Replies
Is it possible to pump up to about the frost depth and
gravity drain from there to daylight?
No - there isn't a 30"
No - there isn't a 30" differnce in slope anywhere in the yard. at max there is about a 1' - 1.5' drop off 50' from from the house.
You don't need much drop into the typical sump. You want to slope the tile a hair (maybe 1/8" per foot) but you generally then bring the tile directly into the pit (near the top) without added slope. So the bottom of the pit is less than 2 feet below the bottom of the tile.
If the pit is kept covered with an insulated cover, and the water level is well below the frost line, then you USUALLY don't have to worry about freezing. You can provide a little "insurance" by installing a second insulated "cover" (loosely sealed) about halfway down the pit, somehow suspended on brackets in the side of the pit. (This could just be a piece of styrofoam cut to fit.) You can also consider installing some sort of heater on a thermostat.
To keep the outlet line from freezing you need to make sure that it never contains standing water. This means no foot valve, a vent at the highest point, and positive drainage (with no low spots) both directions from that point.
Question: Have you considered placing the pit inside the basement?? This would simplify things in several respects.
Ok- so that clears up on the depth of the pit, and thanks for the tip on the 2nd cover, I read some comment on this sight say just a lightbulb would provide enough heat also (just turned on in the winter).
In regards to the drainage, just pump the water up to the highest point, and ensure there is slope to the egress of the outlet line. in addition, at the highest point ensure there is a way for air to enter the outlet line. Thanks a ton - it sounds so simple, but I will need to put some thought to implement.
To the last point - yes, and I there are a few reasons - 1 - the area that I am excavating is only 1 side of the house (gas lines and sidewalks are blocking my path from the other sides. the side I am excavating is a finished lower level basement, and the sump would not be conveintly located. However, I have considered asking the gas co. to maybe put on an upgraded line, and while they do that I can excavate the entire foundation (and destroy the sidewalks and a little porch), then possibly put the sump in an unfinished piece of the basement.
2 - I am not sure how difficult it is to dig under the footer to run your drain tile back into the house? or is that even how it is done?
You can cut through the footer to install the drain line. A PITA, but doable.
What had you planned to use as the walls for the exterior sump pit since the actual pit will only bring you to the level of the footer? A culvert pipe standing on end might work. You could even forgo the store bought sump pit and just sink the culvert pipe to the bottom of you pit. Drill a couple of drain holes in it as well as the hole for your tile and line the bottom and sides with gravel and but a patio block in the bottom for the pump to sit on.