Is it undersized sump basin or inadequate discharging or both?

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ShinDiors

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Have this single pump/pit to collect ground water from a downward driveway, backyard and neighboring yard inside this below grade sideload garage. arrows shows water direction. All gutters are drained through separate drain pipes goes directly into stormdrain curb side, not contributing to this sump, also not seeing overflow from the roof. Water just mainly come from the above lots (through the retainingwall) and the driveway. Not too much underground water either, so the main problem is the surface water. Pump inside is a Liberty LE50 sewage pump with 2" discharge port, but the piping is only 1.5".

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50 gal sump pit, 20" inner diameter around the top but narrows down a little towards the bottom, 39" deep. The center of that PVC inlet pipe is about 22" above the tub bottom, so roughly at the center height (higher than I thought). The two black draintiles seem to be some kinda of foundation drain at the house's perimeter, I don't really see too much water from them. There is a smaller pvc seems to be the AC drain which is also minimum, the big PVC pipe is the 4inch tube that's buried under the garage concrete connecting the grated channel in front of garage. I think currently the concrete is grated to make this pvc pipe the lowest point. I can't tell the pump starting water level right now since it's only raining slightly, but judging from the sound (incoming water flowing down to hit the water inside the sump fading), I'd say it's set at about that inlet pipe level, around 20“-24”,it stops at maybe 2-3" where I can see the float sitting at the bottom out of the water.
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The inlet 4inch pipe from the grated channel is roughly 23-24 ft, the height drop from entrance (at the channel) to exit (at the pit) is probably 20 inches or slightly less. I would see water pouring out fast when its raining heavily.

The discharging pipe: 38"(from pump up)-elbow-19"(horizontal)-elbow-7"(down to ground level inside crawl space)-33"-elbow-9"-elbow-87"(45degree up)-45degree elbow-11"-right angle elbow (where it exits the cinder block wall), there are two right angles elbow from the pump up then back down to ground level(I think can be eliminated?) to give space for the lid. Obviously a little too small for the pump.
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Symptoms: when no rain, the pit is almost dry with not much underground water coming in, the pump is not running. When it rains the pump is cycling at reasonable frequency but only runs for about 10-15s each time then until the next cycle depending on the incoming water rate, if raining more heavily, the pump runs for 10-15s every 30s, until the incoming water start to back up in the pit and water level rises higher than the inlet pipe, that's when things start to go bad (happens once or twice a year). I would see the water inside sump pit slowly going up above or maintain. Water will then backed up at the grated channel and eventually enter the garage (normally I would see a 3/4 full tub while pump continuously run), and if it gets worse, it eventually would spilled out the tub.

My questions:
1. Is 10-15s on each cycle considered "short cycle"? What is the ideal on time and off time each cycle?
2. What is the normal float switch on water level? My gut feeling is it should not be far away from the inlet pipe level other wise water would backed up in the inlet pipe (basically the pipe itself become water-full)
3.Are these symptoms indicating an undersized sump pit (est maybe less than 20gal volume to pump out for each 10-15s cycle) or is it the undersized discharging pipe (1.5" pipe) or both? I want to start by upsizing the 1.5" pipe to 3" all the way until it taps in the 4" gutter drain underground in my backyard. But if the sump size (usable volume) is the problem, improving discharging may cause my pump to cycle on even shorter time correct?
Any thoughts? Thanks in advance.
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Reach4

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Do you ignore the responses to your earlier posts?
 

ShinDiors

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Do you ignore the responses to your earlier posts?
Don't mean to ignore your reply. I googled and found maybe this section of the forum is the correct place to ask and tried to provide as much information as i have right now altogether. If it's inappropriate I will delete this and update in my earlier post (I did not get any reponse after my last reply in that thread couple of months ago, thought I need to restart).
 

Reach4

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https://terrylove.com/forums/index....mp-sewage-pumps-discharging-capability.84598/ you did not respond, and I did not connect your history. In your case, lesser pumps don't keep up. However a different 1 hp pump could be in order. It would be interesting if you could measure the backpressure while pumping with your current pump. That could help select a better pump optimized to work against that kind of backpressure.

https://terrylove.com/forums/index....filled-with-water-always-external-pump.83131/ Your "If water still comes in the garage, then spend the money for the 1hp one (same 2 inch discharge port size) so no need of pipe change?" question did not get answered. I would think that would be a yes.

https://terrylove.com/forums/index....ground-water-from-driveway.82759/#post-596823 You did ask if you could combine the output of two sump pumps and did not get a response. You could. Each would need a check valve before the junction.

https://terrylove.com/forums/index....ith-run-off-ground-water-from-driveway.82759/ was your main thread that covered the info in this post into the well forum. A 1 HP pump seemed to be in order since your smaller pumps could not keep up. You were not wanting to run a 240 volt circuit because your generator could not drive that.
The plumbing forum was more applicable to sump pumps etc than this well forum IMO. A pressure gauge on the pipe near the pump would be useful in matching a new pump to conditions or to identify if your current drain path has too much backpressure. I suspect there is some kind of saddle fitting that could be used to mount a pressure gauge.
 

ShinDiors

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Thank you Reach4 for bearing with my multiple posts. Initially my plan was to have this 1hp different pump in with existing discharging just to see if it is improving the situation despite the undersized discharging pipe, then i read a little bit more and saw the backpressure problem when using undersized pipe. I went the measure and observe the sump pit and the system (even located the 1.5"exit point at my backyard) so just want to provide some more info to see what is the best compromise I have to solve this problem. Apologize for not responding some of your replies with more info.

I can carry some more info in the appropriate thread and continue from there instead of here.
 

Reach4

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Can you measure the gpm coming out of your existing discharge pipe? How long it takes to fill a 5 gallon bucket or known smaller volume, could give that. That can help analyze. If you do any piping changes consider adding in a tee near the pump where a pressure gauge could be connected. That would help analyze.

Regarding a new path to your drainspout system, that could take part of the load off of your existing drain.
 

ShinDiors

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Thank you reach4. I will try to measure that, need to find a feasible way though as that 1.5" pipe taps into the 4" gutter drain which goes to the storm drain curbside.
 
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