Bridget,
The problem could be ground water. It will take days after a rain for the flow to subside. Looking uphill from you parents home could give some clues as to what has changed. Any development which included construction of homes or offices, landscaping by neighbors or added paving for driveways will add to the runoff problem.

I encourage home owners with sumps, to if at all possible, create a gravity drain from the problem to a working drain, be it the City storm or even down to the street below. Using a good quality pipe such as ABS or thick PVC and plumbing fittings will allow the use of a snaking machine if there are problems with the line later.

With homes I have built, I was able to intercept the water before it entered the dwelling, with the use of pea gravel and perf pipe or with a gravity drain from inside the footings. No pumps were used.

Regards,
Terry

• Canterwood Estates