10gpm pump with 8.6 gallon drawdown capacity tank

[WellNewb]

Hey guys, I currently have a 3/4 hp 7gpm 2 wire submersible pump with a wx-203 pressure tank that has a drawdown capacity of 8.6 gallons with a 40/60 pressure setting. The pump is set 300ft down in the well. I'm not sure of static, head pressure, flow rate etc so I'm not even certain it's a possibility.

If I were to replace the existing 7gpm pump with a 10 gpm pump, would that significantly reduce the life of the pump or just mildly?

Not sure if this math is right but since 8.6 is 86% of the recommended 10 gallon capacity for a 1 minute runtime, this should work out to a roughly 52 second pump runtime.

Maybe i could adjust the pressure switch to 38/60 or 40/62 to get a few extra seconds out of it if it's a big deal?

Thanks a lot for your help!

 

[Valveman]

Why not do 30/60 or 40/70? When I see pressure swings that large I know someone was trying to reduce the number of on/off cycles. However, you are over-stretching the tank bladder, and living with a large swing in pressure. This problem was solved in 1993 by the introduction of the Cycle Stop Valve. The tank you have is much larger than needed with a CSV, but will work fine. You can adjust the CSV to give you anywhere from 1 minute to 8.6 minutes of run time using that size tank, as the CSV only fills the tank at 1 GPM above its constant pressure set point.

 

[Sponsor]

 

[Reach4]

Hey guys, I currently have a 3/4 hp 7gpm 2 wire submersible pump with a wx-203 pressure tank that has a drawdown capacity of 8.6 gallons with a 40/60 pressure setting. The pump is set 300ft down in the well. I'm not sure of static, head pressure, flow rate etc so I'm not even certain it's a possibility.

The theoretical drawdown will be a bit less than that in practice.

What is the minimum runtime now?

If I were to replace the existing 7gpm pump with a 10 gpm pump, would that significantly reduce the life of the pump or just mildly?

What would your motivation be to change to a 10 gpm pump?

 

[Valveman]

Pump/motor companies will only tell you that 1 minute of run time is minimum and 2 minutes is better. It should therefore be understood that shorter run times when running at full load amps is not recommended.

 

[WellNewb]

The theoretical drawdown will be a bit less than that in practice.

What is the minimum runtime now?

What would your motivation be to change to a 10 gpm pump?

The minimum runtime with my current 20 gallon tank is currently 1 minute but that's only because there is a leak in the check valve and/or line causing a 10 second delay for the water to get back to the tank. Under normal conditions it would probably be about 50 seconds. Putting in a 32 gallon tank next week.

Wouldn't more gpm allow us to maintain pressure better under heavy demand like filling the pool while taking a bath?

I don't know anything about the capacity of the well outside of it being 300ft deep so I should probably have that checked out first. I wonder I'd this would increase the amount of sediment we get through the filter though.

 

[Reach4]

The minimum runtime with my current 20 gallon tank is currently 1 minute but that's only because there is a leak in the check valve and/or line causing a 10 second delay for the water to get back to the tank.

After re-reading your 10-second post, I have backed away from that opinion. Since your water pressure holds at 34 during your 10 seconds, another theory is appropriate. Could it be that your nipple to the pressure gauge is partially blocked? Does your indicated pressure continue to rise for a while when the pump shuts off? Often when the pump shuts off, the pressure drops a tad.

In choosing a pump, part of the thing would be to know how far down your water is. Your pump is at 300 ft down, but the water level is higher. The gpm rating is one aspect, and HP is another.

If your water is at 250 ft, a 7 gpm 3/4 hp pump will deliver a lot more water than a 10 gpm 3/4 hp pump.

Wouldn't more gpm allow us to maintain pressure better under heavy demand like filling the pool while taking a bath?

That is probably not normally how you want to size your house pump. You fill the pool so seldom, I presume.

If you go to a bigger pressure tank, not that the fitting to the tank increases from your current 1 inch to 1.25 inches. Not a big deal, but something to plan for.

 

[WellNewb]

After re-reading your 10-second post, I have backed away from that opinion. Since your water pressure holds at 34 during your 10 seconds, another theory is appropriate. Could it be that your nipple to the pressure gauge is partially blocked? Does your indicated pressure continue to rise for a while when the pump shuts off? Often when the pump shuts off, the pressure drops a tad.

In choosing a pump, part of the thing would be to know how far down your water is. Your pump is at 300 ft down, but the water level is higher. The gpm rating is one aspect, and HP is another.

If your water is at 250 ft, a 7 gpm 3/4 hp pump will deliver a lot more water than a 10 gpm 3/4 hp pump.

That is probably not normally how you want to size your house pump. You fill the pool so seldom, I presume.

If you go to a bigger pressure tank, not that the fitting to the tank increases from your current 1 inch to 1.25 inches. Not a big deal, but something to plan for.

I just installed a new pressure gauge and the hole it threaded into was clear. The pressure is steady at 60 once it cuts off.

 

[Valveman]

The minimum runtime with my current 20 gallon tank is currently 1 minute but that's only because there is a leak in the check valve and/or line causing a 10 second delay for the water to get back to the tank. Under normal conditions it would probably be about 50 seconds. Putting in a 32 gallon tank next week.

Wouldn't more gpm allow us to maintain pressure better under heavy demand like filling the pool while taking a bath?

I don't know anything about the capacity of the well outside of it being 300ft deep so I should probably have that checked out first. I wonder I'd this would increase the amount of sediment we get through the filter though.

A 20 gallon tank holds 5 gallons of water, a 32 gallon tank only holds 8 gallons of water. Size pump has to do with how much water you have and how quick you can fill a pool, the tank has nothing to do with it. A larger tank will slow the cycling a little, but also delivers low pressure for longer times before the pump starts.