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Old 07-24-2011, 06:08 PM   #1
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Sump Pump questions


I live North of Chicago and we were hit with some historic rain over the weekend (about 7" at O'hare in just a few hours plus more the next day and a half). I have a plumber coming by in a couple of days to check my system but thought some people around here might have an idea.

Let me start by saying the switch on my main sump pump stopped working so my main sump only runs when I plug it in. If I don't then it will fill up and spill into the backup pit. When that one fills up the backup pit kicks on. Here are some observations after spending more time than I'd care to admit in my basement utility room this weekend:

1) If I manually run the main pump a few times I see there isn't any new water coming through the inlet pipe.
2) If I manually run both pumps (with supposedly no new water coming in from the foundation) both pits still fill up. The main pit fills up after about two minutes and the backup pit fills up after about 5 minutes.
3) I think if I run the main pump, the backup pit fills up slightly.
4) After either the main pump or backup pump runs I here a slurping type of sound as the pit is filling back up. After a few seconds the slurping stops but the pit continues to fill up.
5) If I don't run either pump (and since it has stopped raining), both pits fill up but the backup stops filling up just below the switch threshold. My backup pump is not running constantly. If I manually force the water out (by activating both pumps) the pits will both fill up to this same level
6) Even if I run both pumps a lot (7-10 times) water will still keep filling up the pits at pretty much the same speed (2-2.5 mins)
7) In the past my builder said that the pits are sealed so water from the foundation should only come in through the inlet pipe.

Based on all of this I am pretty confident that one of two things is happening. Either my builder was wrong and water from underneath the foundation is coming up and not from the inlet pipe (less likely since I'd imagine the speed of filling up would slow down). Or that my check valves are bad (on both?) and that the town is very backed up with water so the same water I'm pushing out keeps coming back down. This seems reasonable but why would the water keep stopping at the same level if this were the case?

I'm going to have a professional check this out but for the time being I'm trying to get my head around this so I'd appreciate any thoughts. If I left something important out please let me know.

Thanks.

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Old 07-24-2011, 06:41 PM   #2
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I think both pits are picking up water from under the slab---seldom are sump pit entrance pipes sealed,
so water from under the slab will enter the pit.

I see nothing wrong with that---if you don't have internal perimeter drains,at least some pressure is being removed from under the slab.

Fix the bad switch and leave it alone---all is well.---Mike----

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Old 07-24-2011, 07:08 PM   #3
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Originally Posted by oh'mike View Post
I think both pits are picking up water from under the slab---seldom are sump pit entrance pipes sealed,
so water from under the slab will enter the pit.

I see nothing wrong with that---if you don't have internal perimeter drains,at least some pressure is being removed from under the slab.

Fix the bad switch and leave it alone---all is well.---Mike----
So based on that, if I act as a manual switch (plugging and unplugging for a while) I should see the situation start to fix itself, right?
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Old 07-24-2011, 07:53 PM   #4
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If the back up pit can handle the water I would just let the second pump handle the work.
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Old 07-24-2011, 07:55 PM   #5
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Crazy bunch of rain in the last two days!!! I had to slow down to 30 MPH while driving to Naperville this morning----The wipers could not keep up.--Mike---
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Old 07-25-2011, 06:47 AM   #6
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... why would the water stop at the same level ...
The water will always stop at some level. This level is called the water table. The water table can vary from place to place even within a few feet depending on the material (loam, sand, gravel, clay, etc.) and also on the weather (amount of rain) and other factors too.

You need a sump pump and perimeter drain system at all because sometimes the water table wants to be above the basement floor level. When a sump pump is needed and is operating normally the water table in the vicinity of the pit and also in the vicinity of the perimeter drain lines is temporarily lowered but rises to where it would b in the absence of a sump pump a few feet away.

For now you are lucky that the level the water stops at is before the pit(s) are full. When the pit is empty that means the water table at that location on that day is below the level of the lowest hole or crack or inlet pipe in the pit..

The pit(s) should not be sealed in a fashion that limits inflow to the perimeter drain inlet pipes although they might coincidentally be so sealed given the way they were constructed.
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Last edited by AllanJ; 07-25-2011 at 06:58 AM.
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Old 07-25-2011, 02:21 PM   #7
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The water will always stop at some level. This level is called the water table. The water table can vary from place to place even within a few feet depending on the material (loam, sand, gravel, clay, etc.) and also on the weather (amount of rain) and other factors too.

You need a sump pump and perimeter drain system at all because sometimes the water table wants to be above the basement floor level. When a sump pump is needed and is operating normally the water table in the vicinity of the pit and also in the vicinity of the perimeter drain lines is temporarily lowered but rises to where it would b in the absence of a sump pump a few feet away.

For now you are lucky that the level the water stops at is before the pit(s) are full. When the pit is empty that means the water table at that location on that day is below the level of the lowest hole or crack or inlet pipe in the pit..

The pit(s) should not be sealed in a fashion that limits inflow to the perimeter drain inlet pipes although they might coincidentally be so sealed given the way they were constructed.
That makes sense. So the current water table is higher than when the main pump would activate but lower than when the backup will activate (since the main isn't running). If the main switch was working am I correct that eventually the pump would push all the water from the foundation out and thus lower the water table to a level lower than the first trigger?
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Old 07-25-2011, 03:26 PM   #8
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If the main switch was working am I correct that eventually the pump would push all the water from the foundation out and thus lower the water table to a level lower than the first trigger?
Essentially yes.

Note that new water is always seeping under the foundation from under the yard and other outside locations so the pump has to keep coming on to get rid of this water making its way to the pit and keep the water table under the house low.
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Old 07-25-2011, 06:30 PM   #9
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Another thing that I guess comes into play. I have a very deeply dug basement. My ceilings in the basement are 9.5' high. I'm guessing that means that I'm 2' lower than a 7.5' basement and thus need to get the water table 2' lower than a neighbor who has that 7.5' basement (which I'm guessing is a lot of work after a monster rain like we got). Is this accurate?
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Old 07-26-2011, 07:27 AM   #10
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Theoretically yes all other things including the elevations of the two houses being equal.

But since you said that the water level usually stops before the basement floor level, that means that the water table is almost low enough for your house. (flooding of the far corner of the basement may require that you make the pump start again when the level gets even that high.)

For maximum efficiency of the drain tile system the pump should come on before any of the drain inlet pipes are submerged. Exactly how much of the inlet can be submerged without impairing efficiency depends on the level and sloping of the drain pipes, which geometry is difficult to ascertain.
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Last edited by AllanJ; 07-26-2011 at 07:45 AM.
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Old 07-27-2011, 10:37 PM   #11
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I had a plumber come by today and replace the switch on the main sump pump. He didn't feel there were any problems with the rest of the system including the check valve. He said that what my builder had previously described (water only entering the sump pit through the inlet pipe) as unlikely and not really all that good. He said that there are usually holes in the lower half of the pit so any water accumulated around the sump pit will enter it and that is why the pit was filling even though there wasn't any water entering through the inlet pipe.

He set the float on the main tube higher than it had been previously but still low enough that it will kick on before the water enters the backup pit. With it set this way the pit will probably stay about half filled all the time. When I last checked the pump was still turning on about every five minutes but I'd imagine it will eventually settle in to the level just below the switch activation. I can't think of any reason why this would be a problem but wanted to make sure. I guess it is good that my pump won't have to work as hard to lower the water level the added 3-6 inches and will just kick on when the water gets high enough that it would cause problems. Does this sound reasonable?

Thanks for all of the help. I can't tell you how many friends we have that had flooded basements from this latest rain. It is very reassuring to know that I was able to survive it relying solely on my backup sump pump. Now that I have my main pump working again I hope to get to the point where I can stop worrying every time there is a decent rain storm.
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Old 07-28-2011, 06:25 AM   #12
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If the pump turn on level is changed, give it at least two days before deciding whether the new turn on level accomplished what you want. It takes that long for the water table over the entire area of the route of the perimeter drain pipes and 3 feet to each side to settle down.

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