You'd have to contact a well drilling company to Perk-Test the ground. I don't think that's necessary because there are some 'things' you can do before having to incur that expense.
Believe it or not, it takes quite a while for water to percolate through soil. Then, again, it could be a quick occurance. Depending on soil conditions, I can't tell for sure how long it would take for water to percolate through after a good rain. Clay soil is densest and sandy soil is least dense, with that I've seen pumps run for a week after a heavy rain.
Water travels the path of least resistance. So, for example, if your lot has a 'depression' in it where water can collect, and that spot is, say, 15' from the foundation, it could take DAYS for the water to make its way underground to the foundation. Then, it has to 'find' the pump pit to be discharged. Yes, the pit actually DRAWS water to it. It's the 'end' of the path of least resistance!
One thing you want to be sure of is that your discharge line isn't situated in such a way that the discharge water is making its way BACK to the pit. BUT, before you go gung-ho and start extending the line, you need to get the Specifications of the pump for 3 critical pieces of information BEFORE you do any work. You need 1) the pumps MAXIMUM discharge line height, 2) the discharge lines MAXIMUM run (assuming your line is 1 diameter, meaning you're not going from a 2" line to a 2.5" line later on, down the line), and 3) the diameter of the discharge line. All this info is important. In short, you just can't have the line going as 'high' as you want (out of the pit), running for as long as you want, and at whatever discharge line diameter you want.
Also, you want to be sure your gutters aren't improperly installed, missing, or leaking. Water should run INTO them; not over, behind, or through any 'seams'. The same goes for the downspouts. And the downspouts SHOULD be extended at least 3' away from the foundation. And the landscaping around the foundation should slope AWAY from the foundation at least 1" per foot for a MINIMUM distance of 3'. This would, in a sense, allow water to 'pool' (if necessary) to a height of 3' before it reaches the foundation. Now, the key is to get the water as far AWAY from the foundation as possible. So, what I said about the 3" is, hopefully, a situation that you only 'permit' where you can't get the water further away than 3' from the foundation.
VERY rarely is the problem you're describing originating from an underground stream. At the same time, it's NOT unusual to hear about pumps coming on 3 or 4 or more times an hour, every hour of every day. However, they aren't necessarily catching water from an underground stream. Broken/Cracked water mains, sprinkler systems, and so on cause your same problem.
I think I've said enough. For now, my best to ya and hope this helps.
Jay J -Moderator
PS: God Bless AMerica!
Well, it depends on how often the pump is running (per hour) over that 2 or 3 weeks, and if it's running 24 yours a day. Even w/o a rain, I'd consider it normal if a pump was to run 1x/hr., 24 hrs a day. That would be a 'symptom' of underground water; not necessarily a spring. If you had a spring, your pump would probably run 4-6x/hr., 24 hrs /day, in Winter and Summer, with or without rain.
The only thing I'd do is consider a backup system. This may mean replacing the pump. You see, if you go on vacation for a week and that pump needs to run BUT the electricity is out, no one's going to be around. The same thing could happen during an 8 hour night's sleep! The 1 time it DOESN'T run, it will cost MORE to probably 'fix' or replace water-damaged stuff than it would for the price of a new AC/DC sump pump. BasementWatchdog.com is sold at Home Depot for under $500. (Christmas is coming!) Personally, I'd forget hooking it up to a gas generator UNLESS your generator is hooked up to the Electricity Utility Service to 'detect' power outages. Your best bet is a system that's DESIGNED to use a battery. Don't retro-fit your existing system w/a battery because it's probably an AC system. An AC/DC system works on AC and can switch to DC when needed.
I can't see where or how your house 'sits' relative to other homes or the landscape. As you already stated, fix the grading, downspout extensions, gutters and leaks and over/underflows, and so on. That should drastically reduce the number of times that the pump comes on. Just don't get 'comfortable' in ignoring the battery backup system.
My best to ya and hope this helps.
Jay J -Moderator
PS: If you want any piece of mind, check w/your Homeowner's Insurance Co. to see what they cover in the event that your pit's water backs up into the house ...
PPS: God Bless AMerica!
One thought; Do you have a check valve installed in your discharge line? If not, whatever water that remains below the head will run back into the sump and it may be just enough to restart the pump; add infinity. Note: "head" meaning the greatest heigth the pump lifts the water before the first elbow.
I had a couple of conversations with well contractors and one with a geoligst friend. The well contractor said if indeed you had a spring or an underground stream closeby;( Underground stream meaning one that used to be above ground but was buried when your home was built.) Your pump would run constantly. The geoligist came up with the opinion that depending upon your geographical location, the soil make-up around your home, and the drainage system installed around your foundation would all be contributing factors to your problem.
Check with your local planning board to see if they posess a copy of the submitted blueprints of your home and a copy of the Envorinmental Impact Study required before building. This will give you an idea of what the flood plain in your area is like and maybe answer your question. Little reasearch on your part though. But it could be very educational. My Mom used to say that my head was filled with an abundace of useless knowledge, but today, it serves me well.
Good Luck, Len