Some tend to run a lot, although every 7-8 minutes seems rather excessive, as said above have it checked.
My uncle built a house near a small river, or more accuritly on the flood plain of said small river!
His basement is rather large, probably 1,500k sf and he has three sump pumps.
One is a built in back up...
I don't know about your state laws but in CT if you are not given the disclosures its a $300 fine to the seller at closing. One attorney recomends to all his clients to not provide them. However this just seems to cause friction with the buyers.