About To Drill Well - Have Some Questions

[Valveman]

I don't understand this. Are you saying you'll have 41 psi of air in the tank but no water?
Up here we have pressure tanks (ballast tanks) that have an air bladder in them (so the air doesn't diffuse into the water). When the power goes out this will push the water out until the pressure is near zero.
Some say that a 30 gallon tank might hold 20 gallons of water and 10 gallons of air when it's pressurized ( say 50 psi cut-out (off)) and you can draw off about 10 gallons before it cuts-in (on) at 30 psi.
But if the power is out it will still push water at 30 psi and lower to almost zero psi (but at a flow rate that slows with the pressure drop)
There's good information on the charts at the bottom of this webpage: Water Tank Size - how much water is in the water pressure tank? How much water volume do we need to avoid short cycling the water pump?

With a 40/60 pressure switch setting you need 38 PSI air charge in the tank to get the maximum draw down from a pressure tank. With the correct pre-charge of air a 30 gallon size tank only holds 8 gallons of water. An 80 gallon tank only holds 22 gallons of water, and so on.

So if the pressure is at 41 PSI when the power goes off, there is only a gallon or so left in the tank. When the faucet is opened, the pressure will drop from 41 to 38 slowly as the 1 gallon of water is used. Then when the pressure gets down to 38, the bladder in the tank will hit the bottom and the pressure will drop from 38 to zero in less than a second.

There is no water in the tank below the 38 PSI air charge. The system was counting on the pump coming on at 40, but since the power is out and the pump did not start, the tank will bottom out an be completely empty at 38 PSI.

 

[Pettrix]

So does Grundfos make a 20 or 30GPM constant pressure variable speed pump? Or does it only come in 10GPM?

 

[Valveman]

So does Grundfos make a 20 or 30GPM constant pressure variable speed pump? Or does it only come in 10GPM?

Not anything larger than a 1.5 HP in the SQE. But they do make a lot of constant speed pumps of any size, and a CSV will make any of them into a constant pressure system.

 

[Sprinklerman]

The constant pressure pump is great . I do irrigation systems for homes . When someone has one , they can shower while the irrigation is running and there is no difference in flow or pressure .

 

[buickanddeere]

Constant pressure system or not. The tank should be no less than 20gallon on constant pressure and 40gallon plus for a cycling system.
A three phase pump in the well is more reliable than a single phase motor. Even if the single phase is three wire with the starting relay up at the tank.
The three phase pump receives it's power from it's constant pressure controller which is just a variable frequency drive. The constant pressure drive is supplied with 240V single phase from your utility or generator.
The generator will start a constant pressure pump much easier than a cycling pump.

 

[Qapla]

I have been "resurrecting" a well system that has not been used for many, many years. I have had to use a generator to operate it. This well has a 2 hp pump and I have not experienced any problems using the generator.

As to cost, compared to Florida, your prices are HIGH.

I have used a number of 1.5 hp pumps that deliver 25 gpm at 40 psi and they only cost me $450 dollars at the irrigation supply.

I would rather use a CSV instead of a variable speed pump. If you call the people at Cycle Stop they will take the time to explain the why's and how's of both types of systems. (I do not work for them, I just use their products)

If having water in the event of a power outage were a real concern (like frequent power outages) - I would use a simple, less expensive pump down the well even if it did not deliver high GMP. I would have that fill a non-pressurized storage tank. Then I would use an above-ground pump to send the water from the storage tank to the house. This is a common practice in Florida when the well has sulfur in it - the use of an "aerator" (in this case a tank that the water is "sprayed" into and is vented at the top to allow the sulfur smell to escape). In some of these systems there will be more than one 1/2 hp pump drawing water from the storage tank and sending it to different locations. It allows for various pressures, if needed. In one installation, for example, we have one well delivering water into such a tank. That water is being fed to a barn and two separate houses by means of three 1/2 hp pumps. Each place has full pressure for their system and is never affected when one of the other systems uses water.

 

[Pettrix]

I would rather use a CSV instead of a variable speed pump. If you call the people at Cycle Stop they will take the time to explain the why's and how's of both types of systems. (I do not work for them, I just use their products)

Why is a CSV better than a VSP?

 

[CurlyDave]

The pricing seems very good compared to Southern Oregon, which would be about 1.5 times that cost. Grundfos is a well-known reputable manufacturer of well pumps.

What is the use for the well? Household water only, household plus minor irrigation (maybe 1/4 acre) or are you intending on a lot of irrigation?

10 gpm is a lot of water. A huge amount. For two people, our household use is about 175 gallons per day, with no attempt at conservation. This is less than 7.5 gallons per hour, less than 0.15 gpm.

Of course, the type of pump you are looking at has to be able to produce at the highest consumption rate you will have which I would take as 2 showers at once, or ~6 gpm. The pump is fine.

I do not understand the hand-wringing over water during a power outage. Is the generator you are going to use during construction going to evaporate after construction? Keep it and use it to power the pump during power outages. In fact, the sizing of the generator really should not be controlled by construction needs, but it should be able to power the well plus vital circuits in your house. This will cost only a small amount more than a construction generator, and will serve as a nice backup generator after construction is completed.

I did this when we built 8 years ago. I go a conversion kit and the generator that ran on gasoline during construction now runs on propane and is our backup.

Our well is too far from the house to use the same backup generator, so I have a second one for the pump. When I did the final install of the electricity for the pump we did not hard wire it all the way. Grid power comes to a sub-panel and we have a 240 Volt dryer outlet next to the pump control. A dryer cord plugs into this and can be rapidly unplugged and plunged into the generator when necessary. I like to tell our prepper friends that I can turn one gallon of gasoline into 500 gallons of water. They all want to know how to do that, and i explain that I just use it to run the generator and power the well.

 

[redman135]

Grundfos has a reputation for reliability. Be careful about a bigger pump as if you overdraw (pump out water faster than coming in) you will run the pump dry and damage or kill it.

 

[Valveman]

A three phase motor is a tiny bit more efficient than a single phase motor, but it is not more reliable. The electronic and complicated nature of a VFD makes it even less reliable. And generators don't get along with VFD's very well because of the harmonics created by the VFD.