Well Pump Sizing??

[tommu56]

The important metrics are (1) depth of water, NOT total well depth, and (2) desired GPM. If your well head is deep, then you need bigger pumps, however, if your well head is shallow (can you look down and see water?) then a too-big pump will cavitate and damage itself. The pump, regardless of depth, only pumps from the head level, not from where the pump itself sits. Every pump has a head depth vs. GPM curve. If your head is less than the lowest end of that curve, you can damage the pump. You can add pseudo-depth if required, however, by adding additional check valves in series (one at pump, one at pitless, one at tank - usually does it).

A typical residential pump runs about ~7-10 GPM or so. Pick a desired GPM, estimate your well head depth + line losses, then go to a plumbing supply house and they'll pick out the right pump for you. Gould is known as the best pump brand to get in this area.

Pumps usually last about 25 years. I wouldn't worry about filling a 1 acre pond, especially if the pump was running wide open the whole time. What kills a pump is start-stops, so short-cycling due to a bad pressure tank will significantly shorten lifetime.

JayC

If the pump is too larger and doesn't have enough head it will not go in to cavitation
It will go in to over current and burn up if not protected because it is designed for a given head and it isn't there.

A submersible pump normally wont go in to cavitation because the water over top of the pump makes volute a positive pressure,
The lack of pressure in a pump volute reduces the boiling point (think opposite of pressure cooker or radiator cap)
causing a "sand blasting" in the pump as the water burst into a boil.

tom

 

[Egon]

It will go in to over current and burn up if not protected because it is designed for a given head and it isn't there.

Wouldn't the amperage drop when less water is pumped?

If the motor is on the bottom of the pump it should stay in water and be cooled.

If the motor is on top of the pump it can be left sitting without any cooling water and overheat

The pumps are usually sized so as not exceed the recharge rate of the well.

 

[tommu56]

Wouldn't the amperage drop when less water is pumped?

If the motor is on the bottom of the pump it should stay in water and be cooled.

If the motor is on top of the pump it can be left sitting without any cooling water and overheat

The pumps are usually sized so as not exceed the recharge rate of the well.

I don't know all the engineering stuff most what I learned was from fire house training and repairs at work.
When the flow from the pump stops the pressure will go to the top of the pump curve (called dead head) if the motor was selected correctly it will just sit there and the motor will drawl full current.
With no flow the consenquences are the water churning in the pump will heat up and it does it faster than you will think .

When the inlet of the pump has a higher than designed pressure (more water in well) the centrifugal pump will increase the flow and only over loadI cant explain why but that is how it works in real life.
I probably have changed 5 or 6 pumps or motors in my 30+ year carer because they weren't selected right and burnt up due to not enough head.
tom

 

[Egon]

When the flow from the pump stops the pressure will go to the top of the pump curve (called dead head) if the motor was selected correctly it will just sit there and the motor will drawl full current.

When the pump is dead headed the amperage drops. Check it with an amp meter.

With no flow the consenquences are the water churning in the pump will heat up and it does it faster than you will think .

Yes, the water will heat up.
In some cases restricting the pump outlet flow is used as a means of flow control.

When the inlet of the pump has a higher than designed pressure (more water in well) the centrifugal pump will increase the flow and only over loadI cant explain why but that is how it works in real life.

The actual work the pump does is figured from the well water level. Addition work will be from friction loss in the line below the well water level.

I probably have changed 5 or 6 pumps or motors in my 30+ year carer because they weren't selected right and burnt up due to not enough head.

There is insufficient flow through the pump to provide the required cooling.

 

[tommu56]

When the pump is dead headed the amperage drops. Check it with an amp meter.


Yes, the water will heat up.
In some cases restricting the pump outlet flow is used as a means of flow control.


The actual work the pump does is figured from the well water level. Addition work will be from friction loss in the line below the well water level.

There is insufficient flow through the pump to provide the required cooling.

I haven't figured out how to brake the Quote up


You are right my fingers didn't put what my brain was thinking
What I was trying to convey that current will be there (although not full) even with no flow.


I was referring to the motor burning up in the last statement not the pump head it self

tom

 

[dieselscout80]

Didn't....went up to 1.5 hp from 1 hp.

Sorry I thought when I glanced at it you said 1/2 HP. :confused2:

Well how do you like the extra power of the new pump?

 

[Egon]

I was referring to the motor burning up in the last statement not the pump head it self

That can happen when the downhole pump capacity is greater than the recharge capacity. The motor needs the fluid flow to cool itself.

 

[TheGoose]

My advice is to just go with the flow. Even though you are adding fixtures etc. the chances of them all being on at the same time is low.

Sometimes you can tell the HP of a pump by looking at the control box. 2-wire pumps do not have a control box but you can look at the amps to see what HP the pump is.

The lifespan of a pump is certainly not 25 years, although I have seen a few outlast that number. The current lifespan is around 7-15 years, depending on use and brand.

You can get 4" pumps up to 7-1/2 HP.

I wouldn't worry about it. Just rock on until you either notice that it's not keeping up with demand or it gives out, then talk with your well driller/pump guy and let them do the job. It's NOT a DIY job.

 

[dieselscout80]

Will a higher HP pump that is not having to work as hard last better than a lower HP pump working at max capacity?

 

[Egon]

Will a higher HP pump that is not having to work as hard last better than a lower HP pump working at max capacity?

With a downhole pump that runs at a constant rpm it will always be pumping at a fixed rate[hard as it can] unless it runs out of liquid to pump.