Sump Pump Basin Sizing

Discussion in 'Pumps and Tanks Well Forum & Blog' started by soccer123, Apr 11, 2009.

  1. soccer123

    soccer123 New Member

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    I have been looking for a larger sump pump basin but not a deeper basin. I have the standard 18" diameter by 24" deep basin. I would like a WIDER basin to help increase the pumping time but not deeper than the 24".

    The 1/2 hp Zoeller pump runs continuously at the bottom of the sump basin and the two 4" intake pipes are flowing about 50% full. At the top of the sump basin the pump runs for about 10 minutes and rests for about 40 minutes. Does this mean that my current basin is too deep?

    I would like to add a second pump but there is not much space left in the current basin. I have found 24" and 30" diameter sump basins but both are 36" (or more) in depth.

    thanks for the help
    :)
  2. cacher_chick

    cacher_chick Test, Don't Guess!

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    I've found the same problem. Perhaps the easiest solution might be to make a basin from a plastic barrel or section of culvert. If you need a good top, you could always buy the basin that is too deep and then backfill it to the level that you want.
  3. SewerRatz

    SewerRatz Illinois Licensed Plumber

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    Location:
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    There are companies that will custom make a basin for you. But lets look at the situation you have. You say it takes your current pump 10 minutes to clear the basin before it shuts off. Then it takes 40 minutes before it has to run again. The 40 minute rest time leads me to believe the pit is properly sized but the pump is the wrong type for the job. So here are a few questions to help me understand what you have.

    • OK you already said you have a ½hp pump I assume its a M98?
    • What is the total head (total vertical pipe from the pump to where it goes horizontal) the pump is dealing with?
    • The outlet of the pump where does it discharge? into the sanitary sewer? Outside into a small flex hose? Outside into a 4" submersed pipe that drains off away from the house?
    The answers to the above questions will help a whole lot.

    Making the pump pit deeper does not really effect the run time of the pump and or the time it takes to turn back on. The width of the pit does affect the run time and the time between cycles. The biggest problem people have is the pump short cycles meaning as soon as it turns off it turns back on in less than a minute. Ideally you want to have a off time in the cycle during full in-flow of water two be around 5 minutes or longer.
  4. cacher_chick

    cacher_chick Test, Don't Guess!

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    In retrospect, if your pump is really pumping for 10 minutes to clear an 18x24 basin, I would say you have have a bad pump, a restriction, or severely excessive head.

    An 18x22 basin will hold 22 gallons of water. If your drain tile were 6" and 150' in length, "1/2 full" would be about 91.5 gallons. This equals 113.5 gallons total, if the system is being completely pumped out. (which it's not)

    Even the smaller 1/3hp Zoeller 50 series pump will pump 34 GPM with 10 feet of head. This means that 113.5 gallons should be pumped in less than 3.5 minutes.


    The problem with making the pit deeper in our area is that the water table comes up to within a foot of the slab every spring.
    Last edited: Apr 11, 2009
  5. soccer123

    soccer123 New Member

    Messages:
    11
    Sump Pump Answers


    Thanks for your help
  6. soccer123

    soccer123 New Member

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    The 10 minutes of pumping is to clear the top 1/2 of my sump basin. I have moved the pump up so that it starts near the top of the basin and stops just below the two 4" intake pipes. These pipes are flowing about 50% if the water level in the sump basin is below them. By pumping above them the water spreads out in the crushed stone under the cellar floor which delays the flow into the sump basin. The 10 minutes is also pumping the water that has collected in the crushed stopne near the sump basin. My basement is 44' x 77' and the 4" drain pipe goes around the inside perimeter. I suspect that the water table is about 1 foot below the slab in my basement. Is there a way to tell for sure? I tried pumping continuously for 4 days without a noticeable slow down in water flow. I am looking for a soultion where the pump does not run continuously. Raising the pump has slowed the pump but it is scary to see the water at the top of the sump basin.
  7. soccer123

    soccer123 New Member

    Messages:
    11
    Sump basin level?

    Where should the top of the sump basin be?

    My sump basin is about 6" below the (top of the) basement floor and about 2" below the bottom of the concrete slab. I would like to raise the sump basin up to the level of the basement floor. I am only pumping the top 1/2 of the sump basin and this would give me 6" more of useable sump basin.

    Is there a flaw in my logic?

    thanks for the help.
  8. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    OK if the pump is sitting on the bottom and you where getting the 10 seconds on and 10 seconds off that is an issue of an undersized basin. Raising the pump higher into the pit is where the water has to get over the drain tiles to turn the pump on is using the drain tiles as a holding area which is why it takes 10 minutes to clear out the water.

    Raising the pit above the floor so you can make the turn on level even higher than it is now would be a mistake. IF the after gets any higher your drain tiles are already full and with the higher turn on point you will start to notice seepage in the low spots of your basement. To properly solve your problem is a larger diameter pump pit, do not worry about it being deeper, that will not hurt at all. I would install a 36" by 36" basin. This way you can install both your ½ hp pumps and use an alternator. This way each pump gets to run every other time. The alternator also has a high level float that when activated will apply power to the other pump. Below is a picture of this alternator.
    [​IMG]
  9. cacher_chick

    cacher_chick Test, Don't Guess!

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    The math still does not work- 10 minutes pumping is well over 300 gallons of water. Maybe it's a houseboat?

    I don't disagree with SewerRatz about the value of the dual pump system, but I think you are on the right track in not setting the pump(s) any deeper than they are now. For you there might be a fine line between pumping excessive groundwater and pumping just enough to keep your foundation dry.
    A bigger basin means your pump will need to pump longer, but setting the pumps deeper only has you pumping water that does not need to be pumped. The static pressure of water remaining in the tile and basin will slow the flow, which is good as long as you maintain the water level to a point below the lowest point of the slab.

    I would much rather see a pump run for 10 minutes at a time than 30 seconds. The set-up you have really is working pretty good. Short-cycling is what kills the pump.

    How many months of the year does your sump run like this? It sounds like you have a high water table or else are in a low spot and your basement was dug too deep. In that case, the ground water is flowing through the soil around and under your home, much like a river.


    Off topic, but pertinent- Make sure you are not recycling the sump water back to the foundation- the discharge should be on the downhill side of the house, at least 20 feet away from the foundation.


    This I don't understand- the top of the basin has been flush with the top of the slab in my limited experience. In any case, you want the water level to stay below the bottom of the slab.
    Last edited: Apr 12, 2009
  10. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    You are not taking in account the square footage around the drain tiles. If the water has to rise over the drain tiles to turn on (remember he is saying between cycles there a 40 minute rest time) The water is pooling up under the floor and around the drain tiles. Which explains the 10 minute pump time.

    Every pump manufacture tells you that you need to make the pump pit deep enough to prevent the above situation. They say do not have it where the pump turns on above the inlet pipes. A deeper pit will not change what water he is pumping now. Pump pits are sealed except where the drain tiles enter the pit. If he lowered his drain tiles as well then there would be an issue of pumping more ground water than needed. Also the manufacture prefers a short run time a long rest time verse a run time of 10 minutes or longer. IF they wanted a longer run time the would use a duel float set up like they do in lift stations. the lower float turns the pump off the upper float turns it on. So you would set the lower float to turn off when there is only 2" - 3" water left in the pit, you set the on float up high enough to where you get the longest run time. But they do not do it this way due to cast to the home owner so they spend lots of money in engineering their pumps with a automatic pump switch that when installed in a properly sized pump pit it will have a long useful, and reliable life

    I have been working on sizing sump pump pits properly for well into 20 years, and each time it took many hours to get a home owner to understand basic physics, and how a drain tile system works. Most of them too overlook the fact if the water gets above the drain tiles it will pool up under the floor which adds more water that needs to be pumped out hence the long pump time. You ever have a sump pump fail and you ended up with some water in the basement? Lets say their was 1" of water on the floor, when you install the new pump and it fires up that inch goes down pretty fast. But the n it looks like the pump is not doing anything anymore, that is due to the water under the slab is draining into the pit as fast as the pump is pumping it, then it starts to catch up and it takes 20 minutes before you can even see the drain tile. Once the drain tile is visible then the water starts to go down with a vengeance. Then the pump turns off finally and cycles for the next few hours to catch up with all the water that needs to seep back into the drain tiles.
  11. cacher_chick

    cacher_chick Test, Don't Guess!

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    Location:
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    SewerRatz, what you have said makes sense.

    Can you direct me to anything written from a reputable pump company that specifies the ideal run time of a sump pump? It has been my understanding that quality pumps were rated for near continuous duty (as long as they are properly cooled) and short cycles drastically reduce the life of any electric motor.

    As long as the water level stays below the slab, I don't see any benefit to pumping it down much further. If the water table is 1/2 way up the drain tile, it would be fruitless to try to pump it lower. (not to mention the energy used).
  12. soccer123

    soccer123 New Member

    Messages:
    11
    Two sump basins?

    Is there a disadvantage to having two 18"x24" sump basins next to each other if they are connected by a short pipe?

    The two sump basin solution might be easier to achieve given the ammount of water that is coming in (approx 15-20 gal/minute).

    Basement flooded last night - In my effort to prevent a problem I inavertantly caused it to happen. The VerticalMaster switch did not turn on last night. SewerRatz described acurately what happened after I started the pump - In about 1 hour the water in the basement was pumped down and I vacuumed the remaining water with the shop vaccum.

    Thanks again for educating this homeowner to better "understand basic physics, and how a drain tile system works."
  13. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    lol, you are welcome. I am surprised people can follow my train of thought when I type. My mind goes 100 miles per hour and I have a hard time putting into words what I want to get across.

    Casher Chick Give me a couple days to scan my Hydromatic and Zoeller sizing sheets into the computer. The PDF's will be of great help to all.
  14. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    I have seen where some areas (Munster Indina) have the drain tiles drain into pump put #1 and then heads off to pump put #2 to get pumped out. Here is a drawing that explains the way the second pit should be installed. The second pit is the one with the pump in it.

    [​IMG]
  15. soccer123

    soccer123 New Member

    Messages:
    11
    2 sump basins with 2 pumps

    It sounds like there is no disadvantage to having two 18"x24" sump basins. Am I correct?
    I would like use two sump pumps because I am pumping so close to the basement floor. Either 1/2 hp pump would be atequate to keep the basement dry and the duplication would give me extra protection against flooding (i.e. both pumps would have to fail for the basement to flood).
    Is there a prefered way to stager the pumps?

    Thanks again.
  16. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    You can have a pump in the first pit as well. Just note the pipe connecting the two pits is located at the bottom of the pits. This way they both fill up equally. I would install both pumps at the same height, and use the alternator I posted. This way both pump would get the work out every other turn on. and if the water gets two high and activates the high level switch it will sound an alarm and energize the other pump.
  17. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,706
    Location:
    Chicago, IL
    The way this unit works is you plug in both your automatic pumps with their switches intact. The alternator will automagically turn on one pump then the other on each pump cycle. The switch pictured is a high water alarm switch in case a pump fails it will sound an alarm and energize the other pump.
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