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Lots of snow has been melting over the past week. Sump pit was filling up and seemingly the pump wasn't getting water out efficiently. I cleaned some debris away from the pump's impeller area and reinstalled pump which at this point was fully submerged. The water immediately started pumping out in to the draining pipe outside at a pretty good rate. The water level immediately dropped a few inches but has slowed down considerably since then. It has dropped about an inch in the past day with the sump pump running consistently (not cycling, just running). When I had the pump out, I checked if the impeller would switch on and off with moving the float up and down and it was fine. As I said, the water is seemingly getting pumped out and emptying very well into the outside drain pipe leading away from the house. But water level is still at 12" which submerges the inlet pipe by slightly more than half. Am thinking the pit should have drained more than it has after 2 days of continuous running. Wondering if the draining pipe is damaged and causing the water to leach straight back down to the foundation? Any thoughts?

Chris
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    The sump pump can only pump out so gallons per minute. If it is coming in at the same amount(heavy snow melt), then be glad the pump is keeping up. – crip659 Jan 28 '24 at 18:35
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    Is the behavior unusual given similar conditions in the past? Is the volume of melting snow a unique condition? Do you not have much experience with the system? Is there a giant hill sloping toward your property? – popham Jan 28 '24 at 18:45
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    Do you know what happens if you turn off the pumps? Is there a high water table that rises up into the basement? Or are you mainly collecting groundwater flowing into the pit from French drains? Or some combination? The pump size and pit depth needs to be set according to those factors. – jay613 Jan 28 '24 at 18:47
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    I'd throw some dye in the drain pipe to see if it drains into the sump – Martin Jan 28 '24 at 22:13
  • How do you know the pump is actually moving water? Can you see the end of the outflow pipe? – Tony Ennis Jan 29 '24 at 16:17

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This sounds perfectly normal, though I might inquire about whether the output pipe is really taking it far enough away, in a direction free to drain away from the house. If it does not, you can end up pumping the same water in circles.

But in general, when you are pumping groundwater, the ground has a lot more water than you have pump. So the sump lowers the level of the groundwater in the immediate area of the house, but there's plenty more where that came from, and it will tend to run until the general groundwater level drops. Nothing unusual about that.

Ecnerwal
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  • I never thought of it this way. It's really helpful. For a high water table I think you're saying, the deeper you go the faster the groundwater will flow in, so no matter what size pump you get, it will pump down to the level where the inflow is equal to its capacity, then just keep pumping. So you in fact don't want a bigger pump. You want one just big enough to handle the inflow at a level just below your french drains. Anything bigger will just work harder against higher flow at a lower level. YOU didn't say all that but it seems to follow? Does it? – jay613 Jan 28 '24 at 21:44
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    Well, if you get one that pumps faster than the water flows in, it will shut off. And turn on, and shut off, and turn on. Which is also normal, and part of that is what the flow resistance between the outer world and the pit is. Most people are prone to putting in a big pump js in case, but if the pit isn't big enough (or the turn-on point is set too low) that can lead to short pump life from "short-cycling." If you're concerned that the pump you have is not big enough, it's better to have a pair of pumps and a smart controller that switches between them, or different float settings. – Ecnerwal Jan 28 '24 at 21:52
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    If you choose different float settings, you should manually adjust which pump has the lower turn on every once in a while, so one pump does not sit idle for years and then not work when needed. The smart (not in the internet of hackables sense) controller does that by switching pumps every time it turns on, and turning both on when one can't keep up, But they are expensive. – Ecnerwal Jan 28 '24 at 21:55
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    @jay613, I got some nice pictures that you might want to check out under https://diy.stackexchange.com/questions/286025/basement-flooding-only-with-heavy-snow-fall/286061#286061. – popham Jan 28 '24 at 22:26