We bought our house in December of 2015. House is situated at bottom of the slope (backyard is slopping towards the back of the house not very steep - but still negative slope). House has sump pump pit and drain tiles are opening in sump pump (roughly 8-10" from the top top the floor). Sump pump outlet and downspouts are tied to separate 4" PVC pipe and releasing water close to city storm system - roughly 20-30' away, towards the front of the house. On front and sides of the house foundation, ground is sloped properly (at-least for good 15' to 20'). Backyard is sloping toward the house and there is drainage grass swale (in backyard) which runs may be 10' feet from the foundation and goes to side of the house and water is released toward the front of the house (around city storm system). There is also positive slope from foundation back wall to drainage swale.
After heavy rain, our sump pump runs quite frequently, may be almost every couple of minutes when rain is falling and this continues for next 3-4 days. Also, I see water puddling in the swale and it stays there for few days - swale in the backyard doesn't have steep grading - its almost flat to very gentle grading (towards the city storm system). Currently basement is dry and I don't see any water seepage (I do see efflorescence on wall where it meets basement floor). Sump pump has battery backup but I'm bit concern that if we lose power for extended time during storm then battery backup or generator may not be enough for supply power to sump pump for long duration (since our street is small we get lowest priority when power is lost - according to neighbors, during last storm it took 5 days to restore power on our street). With sump pump running with this high frequency - I'm sure that basement will flood during outage (and basement is semi finished).
I called few basement and landscaping contractors - and got varying opinion from them. Seems like all basements contractors wants to sell french drain system (where they install french drain from inside of the basement) - I'm not sure if that would help me. Landscaping contractors - not confident that they can increase the grade in the swale significantly to alleviate water standing or few thought it may not help at all. Cost to redoing swale is significant and comes without any warranty (wrt improving sump pump situation). Few landscaping contractor thought outside french drain may help with standing water in swale but may not improve anything wrt sump pump running frequency. Some suggested catch basin boxes to address this issue.
Also, 3-5 days after rain - sump pump do not run at all. Soil in our area is clay and water absorbency is not good. Whole backyard and area around the house has lawn and very minimal plants around proximity to the house.As far as I can tell, my next door neighbor's sump pump runs vigorously as well.
My questions are:
1) What system do you experts think will works best for my situation? Inside french drain, outside french drain, swale improvements, catch basins or any other bright ideas?
2) Generally water in sump pump pit stays almost half way to the drain tile opening (sort of point of stabilization). That's how previous owner set the sump pump trigger point. If I bring level below the drain tile opening then sump pump keeps running and I can see drain tile dumping water in pit as soon as its being empty by the pump. Only time I see water level in pit falls below the drain tile is during no rain for extended period of time (almost like drought situation).
3) Could this high water level around basement deteriorate foundation and footing? This house is 16 years old and I don't see cracked floor or any issue with foundation walls or settlement issue. Basement is very dry and I don't smell moisture or anything in the basement. According to previous owners basement was never flooded (but they never mentioned me high running frequency of sump pump). Basement structure withstand this issue for for past 16 years without any issue (which I can tell)- so may be am I overthinking this situation?
4) Few landscaping contractor recommended outside french drain - but not very deep (may be 10-12" deep from top) and they can connect it to exiting 4" pipe carrying downspout water. Do you think its good idea? Way the slopping around the house is - very deep french drain is not a possibility (deeper than 2 feet french drain will not see daylight at exit).
Sorry about such a long post but I wanted to detailed enough for your expert opinion. Thanks in advance.