Need advice on submersible pump size. Pleeeease.......

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Raggare

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Hi all,

I thought I knew what pump size I need, but after seeing the well driller's recommendation I am confused and need some advice.

Well depth: 315'
Well size: 6"
Static water level: 120'
Pumping level (after pumping 9.5 gpm for 1 hour): 150'
Bladder tank in house is basically at grade level.
I want to use a 40/60 psi pressure switch (= 138' head).
It's a 2-3 bedroom house, so I figure I need about 10 gpm.

So I was going for a 10 gpm, 1 horsepower, Grundfos 10S10-15 pump, set at 200 feet.
(This would give me 10 gpm, when pumping against 150'+138' head.)

My well driller recommends a 25 gpm pump, set at 220 feet.
This flow sounds too much to me. Any idea why he wrote this? To minimize starts/stops? To minimize running time? Or maybe he is correct?

I really appreciate any advice you can give.

Thanks,
Per
 

Valveman

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A 25 GPM, 1 HP stops pumping at 210'. The 10S10 will still pump 8 GPM from 220' and 50 PSI. Don't know why anyone would recommend a 25 GPM, 1 HP for that deep of a well, cause it won't work. Stick to your guns and put in the 10S10. Might need to find a new pump man.
 

Gary Slusser

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It's the number of BATHrooms, not bedrooms, and the type of fixtures. Like big jetted tubs and body spray showers and how many of the fixtures are used at the same time. Or said another way, it's the peak demand flow rate in gpm the house needs, or how the family uses water. Plus any outside uses.
 

Raggare

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Thanks for your replies guys! Much appreciated.

valveman, I wasn't clear in my message, sorry.
The well driller doesn't necessarily recommend a 1 hp pump for 25 gpm, he just recommends 25 gpm (not speciifying what pump would be needed).

But please explain/confirm one thing to me, I am not sure about this: When sizing a pump, it's the pumping level (in my case 150') that is used, irregardless of what depth the well is, (315') or what depth the pump is set at (200')? Am I correct?

Gary, I believe you are correct.
It's the family needs that are important. I used the "rule of thumb" rather than add up all the fixtures etc. But I think my needs are pretty average, no real big water consuming tubs or showers.
Do you think I need more than 10 gpm? I can easily go for 16 gpm if that's what's required.
But I can't really see why a 2-3 bedroom house would need 25 gpm, like the well driller recommends.

I guess my question is: Can anybody see a need for a 25 gpm pump for an average 2-3 bedroom house?
 

Gary Slusser

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Gary, I believe you are correct.
It's the family needs that are important. I used the "rule of thumb" rather than add up all the fixtures etc. But I think my needs are pretty average, no real big water consuming tubs or showers.
Do you think I need more than 10 gpm? I can easily go for 16 gpm if that's what's required.
But I can't really see why a 2-3 bedroom house would need 25 gpm, like the well driller recommends.

I guess my question is: Can anybody see a need for a 25 gpm pump for an average 2-3 bedroom house?
You keep talking BEDrooms instead of BATHrooms.... and you don't mention how many people or their ages, whether they shower or are talking tub baths every day while the laundry is running non stop along with the dishwasher and ice maker.... so let me ask you, how much water do your BEDrooms use daily?
 

Raggare

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LOL! And actually my bedroom hose bib is leaking pretty badly too, so I need a big submersible.......and then big sump pump to pump it outside!

Joking aside, you are of course correct I shouldn't be talking bedrooms.
I have 2.5 bathrooms, and it will be me, the wife, and our 13 year old son.

And I have checked a bit more and found where it recommends the number of bathrooms times 5, which in my case would be 3 x 5 = 15 gpm. Maybe I should go for a 16S10 rather than a 10S10, 16 gpm rather than 10 gpm, but still 1 hp?
 

Valveman

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A 1.5 HP, 16S15 can do15 GPM, which is a lot for 2.5 baths. It would take a 2 HP to do 25 GPM, which I think is way overkill. The bigger pump will INCREASE starts and stops, and DECREASE run time. Are you sure this is what the pump man said??? If so, I would question everything this pump man says and does!

You didn’t say anything about the tank size? You would need a minimum of a 60 to 80 gallon size tank for 1 minute of run time with the 1.5 HP. You would need a minimum of an 80 gallon tank for the 2 HP to have a minute of run time. And 1 minute of run time is the bare minimum. 2 minutes is better, which would mean twice the size of tank I mentioned. The bigger the pump, the bigger the tank must be to limit the on/off cycles.

Now that is the old way of doing things. As Porky mentioned, you can use a Cycle Stop Valve with either of those pumps, which would work with as small as a 4.4 gallon size tank. This way you can install as large a pump as you think you may ever need, and the CSV will make it work like a small pump when that is all you need. The CSV will let the pump work down to as little as 1 GPM, while maintaining 50 PSI constant. So there is no cycling on and off, even with a 4.4 gallon size tank. With the CSV, your run time is the same as the length of time you are using water, plus the time it takes to refill the tank at 1 GPM. So even with a 4.4 gallon size tank that only holds 1 gallon of water, your run time is always 1 minute more than the length of time your faucet was running.

Even a 60 gallon tank only holds 15 gallons of water. So your water doesn’t come from the tank, it comes from the well pump. The tank is only there to limit the on/off cycles, and insure at least 1 minute of runtime. The CSV does that for you, so you don’t need much of a tank.
 

Raggare

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LOL! You may be on to something here! I must admit I never thought of that.

Anyway, I will take your advice and stick to a 10 gpm pump. 15 gpm seems a bit overkill.

And I am researching Cycle Stop valves now.

Thanks a lot, your advice (and humor!) is greatly appreciated.

/Per
 
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