Sump wells on the outside of the home
If the yard area that you wish to use for the placement of a hand excavated drywell does not perk well, do not worry. A sump well is your answer. If the area that was chosen for the hand excavated drywell does not perk satisfactorily, this is your solution. In most cases drywells do perk. However, when they are newly constructed they can take a few hours to a few days for the water to soak below grade.
I completed a project this week where in one location the hand excavated drywell perked extremely well because of the rock mixed in with the dirt. The second drywell on this site was located only 40′ from the first drywell, but when it was tested by putting approximately 12″ of water in it, the drywell was soaking down (perking), very slowly even after 48 hours.
The bottom of the drywell was 4 feet deep and had been finnished on a hard basalt rock bottom. The answer to this problem is to first test the drywell after it is constructed, and second create a “sump well” out of the hand excavated drywell if it shows signs of not perking adequately.
Give the new hand excavated drywell a couple of days to show adequate perk break in when it is new. The sump well is plumbed with a sump pump located within the drywell on the exterior of the home, and connected to the collection hand excavated french drains. In this way the water is collected in the normal way with the french drains, and is pumped out before it has a chance to overflow the sump well
.This method is a much better way to collect and vent large amounts of groundwater than trying to excavate a shallow sump pump location in a basement or crawlspace.Even crawlspace sump pumps need interior french drain systems to gravity flow the water that is already below grade to the sump pump for evacuation. If interior sump pumps are a last resort due to the inability to construct hand excavated french drains and sump wells on the outside of the home, then construction of crawlspace or basement sump pumps may be the only alternative.
The key to the exterior sump well construction is having exterior electric power available on the outside of the home. You may hardwire these pumps, but in most cases with the smaller(1/4hp-1/3hp sump pumps) it is not required for functional common sense if connected with a 12 guage contractor grade all weather extension cord within a solid concuit, to a gfci rated electric circuit with protection from the rain.
I recommend a 30 amp circuit if possible. The sump pump in the exterior sump well construction is mounted inside concrete cylinders with a concrete top. It is placed and leveled on a bed of 3/4″-11/2″ river rock. The concrete cylinders are surrounded to the top with the same rock. This draws the groundwater through the rock, and pumps clean water.
Plumb the sump pump with 1 1/2″ abs pipe and vent to to the chosen location. Always install a backflow device on the sump pump as well.