Enlarging sump

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Old 01-21-09, 10:29 AM
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Enlarging sump

I have a bad water problem in my basement each spring. I have a floating slab, with two corregated plastic pipes running into a standard (small) 18X24 sump. With this small of a sump, the pump runs continuously when the water is real bad - it does not cycle at all. I am considering cutting out the old sump and installing something much larger, but I'm concerned about getting in over my head. I would have to cut out the concrete floor, remove the old sump, dig a larger hole, install the new sump, and pour new concrete. What else? What am I missing? Any common pitfalls I should know about?
 
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Old 01-21-09, 10:41 AM
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Enlarging sump

If your pump is running continuously, that suggests that the pump capacity is inadequate and has little to do with the size of the sump.
 
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Old 01-21-09, 10:48 AM
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Thanks concretemasonry, but the pump itself is more than adequate. I'm actually using a sewage ejector pump that is giving me approximately 80 to 100 gpm. Thats gallons per minute, not per hour. And yes, when the water is real bad in the spring, it runs continuously. I've considered petitioning the county to have the ditch out front re-named as an intermittent stream after me. I have a water problem, not a pump problem. The enlarged sump idea is my thought to try to get the pump more of a chance to cycle, and perhaps to consider adding a duplex pump system.
 
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Old 01-21-09, 12:38 PM
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I have a similar situation, although mine does not run continually. During heavy rains, or spring thaw, it will cycle about every 2 minutes. I have looked for a sump bucket that would (ideally) be rectangle. I was thinking 2' x 3' x 2' deep. If you locate anything you think is workable, please post that info here!
Good luck.
 
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Old 01-21-09, 01:13 PM
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Enlarging sump

Sno_man -

When you say "floating slab" does that mean a 4" slab that is poured on the footings and between the foundation walls or is it a thicker structural floating slab that is more heavily reinforced and provides the foundation for the entire home? Cutting into the second type is a more adventurous project.

Making a sump bigger does not necessarily mean the pump will run less because the amount of water provided to the sump determines how long a pump will run after it has be started by the float.

How deep is your sump?

It is not necessarily bad if a pump runs continuously during a very bad period if it is a good pump. Starting and stopping can put more load on a pump depending on the type.

When it runs continuously, is the water level in the sump above the top of the inlet pipes? If it is not, the pump is doing its job, but you could possibly use a better pump. I am not familiar with the pump that you use, but it may have the maximum pumping capacity, but the capacity could be reduced or reduced by the height it is lifting the water to discharge and the back pressure created by the discharge pipe.

How far away from the house is the discharge and how much below the grade at the house?

What is the diameter of your dischage line? The pump is being fed by two lines of unknown diameter. Rigid 4" pvc will deliver more water to the sump than corrugated.

Is the discharge to the surface and running across the yard to a lower area or are you using a pop-up (not likely in your area)?

Are there any utility lines (electric, gas, water, sewer, telephone, etc.) from the street to the house that could intercept the flow and direct it back toward the home? - If so, you could be pumping and repumping your water in a circle. Utility lines and the backfill are rarely compacted well and serve as a great collector since fill material around utilities is always more permeable than the undisturbed natural soil and will collect surface water.

I assume you have an appropriate check valve immediately above the pump.

I ask these questions because they could give you an alert before attempting the very messy and difficult job of enlarging the horizontal dimensions of the sump pit.

Dick
 
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Old 02-02-09, 08:56 AM
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Dick –

Sorry for taking so long to get back to all your questions.

I said it was a “floating slab” because somebody told me that when I purchased the house. It’s been around for much longer than we’ve owned it, so I can’t really say how it was constructed or how thick it is. There is a small gap, maybe 2” or so, between the walls and the floor all the way around the perimeter. Corrugated 3” plastic drain pipes run underneath the entire floor, and connect to the sump in two spots. There is a very long steel I-beam running the entire length of the house, and there are two metal poles from this I-beam to the floor. Everything else appears to be resting on the cinder block walls.

The sump itself is 18” diameter, 24” deep. Very small. When the water comes in very quickly in the spring, it does tend to get above the level of the inlet pipes occasionally.

Here’s my discharge configuration. The pump has a 2” discharge, which goes to a 2” check valve. The total length of 2” pipe, including the check valve, is probably 3 feet. From there, I have increased the size of the pipe to 3”. It goes up another 3 feet or so, then an elbow out horizontally, then another 3 feet of pipe. From there it discharges into a 8” corrugated steel pipe, which runs downhill about 40 feet to the ditch out front. The total drop over that 40 foot run is at least 4 feet. The 8” pipe is about 2 feet underground.

Based on the above configuration, I calculate a total head on the pump of no more than 10 feet (about 7 feet of vertical lift, and well less than 3 feet of friction loss/back pressure from piping and check valve). The pump is capable of lifting up to 24 feet, and at 10 feet it should be giving me about 110 gallons per minute. It is a Liberty LE51A, one of the best pumps on the market, if not THE best.

There are no underground utilities in the area. The only thing underground is the water into the house, which is on the other end of the house, about 30 feet away from the sump. Again, based on the configuration I described, it’s highly unlikely I’m recirculating and/or repumping water.

I don’t agree with your statement that making the sump bigger won’t affect how much it runs. The cycle of the pump is determined by the float switch. When the water raises to a certain level it turns on. When the water level drops enough, the float switch turns the pump off. It is therefore based on a fixed vertical measurement, say for argument’s sake it is 5”. Therefore, the total volume pumped during that 5” drop is entirely dependent on the diameter of the sump; the rate of water coming in only affects the cycle if it is close to the capabilities of the pump, as in my case. 5” in an 18” sump is way less volume than 5” in a swimming pool. My problem is that the water is coming in almost as fast as the pump can get rid of it. In an 18” sump, the pump never has a chance to clear it all out. I think I am getting about 90 to 100 gpm in, which is just too much for an 18” sump. I’m hoping that a larger sump will give it more of a chance to actually cycle during high flow, rather than run for days, even weeks, at a time without shutting off.

Thanks for your input, and I hope that you can help shed some light on the “floating slab” description and what will be involved in enlarging the sump. I would love to get the water problem fixed so I can potentially finish off the basement, or at least part of it.
 
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Old 02-03-09, 05:02 AM
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duplex

Since its not my money, here is my suggestiion. Put in a 30 x 36 or 36 x 36 crock and install a duplex pump system. Also have a good quality battery back up installled.
Enlarging the sump crock will allow you to pump alot more gallons of water during each cycle.
 

Last edited by waterwelldude; 02-03-09 at 05:38 PM.
 

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