1/3 or 1/2 hp sump pump?

What factors must I consider on whether I need a 1/3 or 1/2 hp sump pump?
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Joe wrote:

how high do you have to pump it? Either size will do the job for a normal 9' lift.
s
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about 8 feet, is that the only factor or should I factor in how quickly the sump pit fills during heavy rain? Will a 1/2 hp will pump out considerably more water, faster during a heavy rainstorm or is the difference neglible?
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Joe wrote:

Regardless of rainfall rates, the ground will only pass the water at a certain rate. You shouldn't see any real difference in the amount of water running in the sump pit. the 1/3 unit will do just fine. Use 1-1/2" line and a check valve just above the water line to prevent the line from flowing back into the sump when it shuts off.
s
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On Sat, 07 Mar 2009 10:36:05 -0600, Steve Barker

Hi Steve,
I assume that I am misinterpreting what you have written, but...
Sometimes, our sump intake shows a trickle for weeks at a time, and sometimes a veritable river.
What did you mean when you wrote "You shouldn't see any real difference in the amount of >water running in the sump pit"?
I see extremely significant variation...
Thanks for telling me something more.
All the best,
--
Kenneth

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In spring summer, after all is thawed, with a big 2-4" rain I do get alot more pouring into the sump, now the ground is still frozen.
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Kenneth wrote:

I rekon i was just wrong. Sure you don't have a french drain going into the sump system somewhere? My sump flow increases during a rain, but not all that much.
steve
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Mine is a massive french drain with several large 4" inlets and maybe 1000 gallon pit, when it rains it pours in, the pit is maybe 5 feet wide and 6 feet deep
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On Sat, 07 Mar 2009 20:07:10 -0600, Steve Barker

Hi again,
Whew... What was that...? Some Usenet integrity? <VBG> (I really appreciate it...)
No, we don't have a French drain feeding the sump, and we do have the variability I had described.
All the best,
--
Kenneth

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The gallons per minute or hour to be pumped and how high it must be lifted are the two things you need to know. The pump should be rated in gallons per hour at a given lift. If two pumps will meet the requirements and one is one third horsepower and the other is one half horsepower I would go with the slightly heavier duty motor.
An electric motor works hardest when it is starting. To avoid the motor having to start under the full back pressure of the lift a small hole is drilled in the pipe just above the connection to the pump and below the check valve that prevents the water from back flowing into the sump. This allows the pump to start without having to lift the full column of water during the start. When a check valve is used in climates subject to freezing it is important that the piping be arranged so that no water will be left standing in piping that is exposed to freezing. It may be necessary to raise the water higher so that all the piping exposed to freezing will drain to the outside after the pump stops. In extreme climates a dry well may be needed to allow the sump to discharge underground. If you are blessed with terrain that allows underground piping to terminate below your cellar floor then you will never have to worry about a frozen or fractured discharge line. That is also a case were a battery driven back up pump can be fully affective. The back up pump only has to get the flow started and the siphon affect will do the rest allowing the back up battery to last a lot longer. If you have to discharge the water above the level of the sump, like most folks, then discharge it well away from the building. If you have utility provided water supply and are at risk for prolonged power outages, such as in areas subject to ice storms and hurricanes, a water driven ejector; or jet pump if you will; is a better back up then a battery powered pump.
-- Tom Horne
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Tom, that is a very good summary.
Thanks
Any other points on this subject that you can offer?
TMT
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How fast does the pit fill and how many gallons, how high to pump out. On Off cycling is hardest on a pump. I would want the smallest that will just keep me from flooding. I would set the float switch so it runs longest
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Pat, by definition, the smallest one that keeps you from flooding is the correct choice. :)
The pump that "keeps you from flooding" is the right pump.
Now, how to choose that size pump.....is the trick question. Only you know how big your sump is & what sump filling behavior you experience (worst case). But having a decent sized sump you might be able to get away with a smaller pump, depending on rainfall beahvior. In Socal we sometimes get really heavy rain for a day or two (like maybe a couple / few inches). VERY occasionally (once every ten years?) we can get an inch in an hour. House rain gutters (5") can be overwhelmed . On average we get very little rain.
Knowing your sump filling behavior is the best way to size a pump.
If your sump sees input at 1gpm, you dont need a 6000gph sump pump. If you get a couple gpm...you;re going to need a more capable one.
cheers Bob
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Joe wrote:

Read the specs on the boxes.
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I wouldn't focus too much on horsepower...mfr's "fudge" the numbers
Look at gph & head (lift)
How quickly does your sump fill up? What pump capacity do you need to keep the sump from overflowing?
Too large a pump will cycle on/off too frequently.
cheers Bob
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On Sat, 7 Mar 2009 11:23:16 -0800 (PST), fftt

Hi Bob,
Why would they "fudge" HP, but not gph & head?
Thanks,
--
Kenneth

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Kenneth wrote:

because people (consumers) tend to put some kind of stock in HP ratings. And manufacturers tend to LIE their ASSES off about HP ratings. That's why they removed them from gasoline engines on lawn equipment. We're still stuck with the LIES on the electric motor equipment. Used to be (when the HP ratings were accurate) a 3/4 HP motor was about a foot in diameter and pulled 9 or 10 amps, and would last forever. NOW a days, they put a 15 HP sticker on a motor the size of a sewing machine motor that draws 4 amps and lasts about a year.
steve
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Because if the pump moves the amount of water to the height they say it does and it is overwhelmed by the incoming flow they will not have created a cause of action against themselves in civil court. Fudging the horsepower makes the pump sound more powerful to a potential buyer and there are several ways to calculate horsepower. There is only one way to calculate Gallons per Hour at a given lift.
-- Tom Horne
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because gph & head are verifiable by the user..... and horsepower is close to meaningless for the user, all that matter is flow rate & head
shop vacs list all sorts of bs horsepower number....like "develops 3 hp peak" or some such nonsense
on shop vac I suggest looking that that amps, not hp
on pumps....... flow & head (a tabular representation of the pump curve)
cheers Bob
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On Sat, 7 Mar 2009 19:55:12 -0800 (PST), fftt

Hmmm... 'Makes sense. Thanks,
--
Kenneth

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