Well pump GPM

[AaronR]

I own an older home on 2/3 of an acre and I am working on redoing all the outdoor irrigation. I'm starting with trying to determine the flow rate of the well. I have a submersible pump with a 119 gallon pressure tank. I did a flow test utilizing a five gallon bucket and timing rate of fill as described on several websites. My pump did 20 gallons flat and then took 29.44 seconds for pressure tank to fill. This came out to roughly 40 gpm. Did I do something wrong seems way to high.
Thanks for some help.

Aaron

 

[Reach4]

A 119 gallon pump holds around 3o gallons of water and 90 gallons of captive air.

When you did the bucket test, how many seconds did it take to fill the 5-gallon bucket. Was that 15 seconds, which corresponds to 20 gpm?

So a couple factors can be going on. Your bucket filling may have been through a garden hose spigot, which is probably a lot smaller than the path to your pressure tank.

The other think is that your air precharge may be off. What pressure switch setting is your pressure switch -- 50/70, or what? What is your air precharge?

 

[Sponsor]

 

[AaronR]

I didnt count seconds to fill the buckets as the instructions I found indicated that it wouldnt be necessary. Just make sure tank is topped off, fill buckets until pump kicks in turn off spigot and measure seconds for tank to refill. Divide gallons by seconds x60. And it was through spigot.

Pressure switch is 30-50
Pre charge is 33lbs

 

[Reach4]

I didnt count seconds to fill the buckets as the instructions I found indicated that it wouldnt be necessary. Just make sure tank is topped off, fill buckets until pump kicks in turn off spigot and measure seconds for tank to refill. Divide gallons by seconds x60. And it was through spigot.

Pressure switch is 30-50
Pre charge is 33lbs

Precharge should normally be 28. With precharge 33, the tank will hold less.

I think you are saying that with the pump off, the tank gave up 20 gallons. Then the pump cut off at 50, and it took only 28 seconds to get there. When done, the pressure gauge said 50. I agree that your pump seems to be delivering 40 gpm. What can you tell us about the pump?

 

[AaronR]

Precharge should normally be 28. With precharge 33, the tank will hold less.

I think you are saying that with the pump off, the tank gave up 20 gallons. Then the pump cut off at 50, and it took only 28 seconds to get there. When done, the pressure gauge said 50. I agree that your pump seems to be delivering 40 gpm. What can you tell us about the pump?

The only thing I know about the pump is from a handmade note taped to the old pressure tank I had. It stated the well was 100' with pump set at 70' and water at 12' and (stated 25gpm???). Has 1.25" pipe running into the pressure tank.

 

[Reach4]

How many amps is the breaker? Can you measure the amps when running with a clamp-around ammeter? (no need to go buy one, but that would help predict HP. Breaker amps does that too, but not as well.

If you are getting 40 gpm out of a 25 gpm pump, that could cause upthrust. You might put a 3o gpm Dole valve in series with the line from the pump to limit the rate. When you replace that pump, you would use a lower power pump.

In setting up irrigation, you would like to tune each zone to avoid cycling. If running 30/50, change your emitters so that the pump running stabilizes at maybe 40 psi. Alternatively, you can use a CSV which will keep you in the no-cycling area without the fine tuning.

You might be better off turning up the pressure switch to 40/60 or 50/70. You would adjust the precharge accordingly. Yes, the tank holds less water that way, but the pump will deliver less water that way. Plus your sprinklers will throw farther.

 

[Bannerman]

Assuming your pressure gauge is indicating accurately, with 33 psi air precharge in the tank, the tank will contain 0 water @ 33 psi but the pressure switch will not activate the pump until 30 psi. You should have been experiencing a brief loss of water flow from faucets before the pump was activated.

Assuming your pressure tank is a Well-X-Trol WX350 119.0 gallon, the Specifications indicate that tank's drawdown capacity shoukl be 36.9 gallons water @30/50 psi or 32.1 gallons @ 40/60 psi when using the correct air pre-charge for each pressure range.

After shutting off the pump and draining the plumbing system to 0 psi, adjust the tank pre-charge to 2 psi below the pump cut-in pressure (ie: 28 psi for 30/50 switch settings).

 

[AaronR]

How many amps is the breaker? Can you measure the amps when running with a clamp-around ammeter? (no need to go buy one, but that would help predict HP. Breaker amps does that too, but not as well.

If you are getting 40 gpm out of a 25 gpm pump, that could cause upthrust. You might put a 3o gpm Dole valve in series with the line from the pump to limit the rate. When you replace that pump, you would use a lower power pump.

In setting up irrigation, you would like to tune each zone to avoid cycling. If running 30/50, change your emitters so that the pump running stabilizes at maybe 40 psi. Alternatively, you can use a CSV which will keep you in the no-cycling area without the fine tuning.

You might be better off turning up the pressure switch to 40/60 or 50/70. You would adjust the precharge accordingly. Yes, the tank holds less water that way, but the pump will deliver less water that way. Plus your sprinklers will throw farther.

Thanks for the info. I found on tag left by the previous owner 1.5, 25 gpm. So 1.5 hp. It's has a 20 amp double pole breaker.

Maybe a dumb question here but how does a pump rated at 25gpm produce 40gpm?

I am really leaning towards the CSV to simplify the irrigation design.

Thanks again.

 

[Reach4]

Maybe a dumb question here but how does a pump rated at 25gpm produce 40gpm?

If you seek out pump curves, you will see that if the head is low, that is the way they work. 25 gpm is not a max amount on a good pump, but rather the gpm where the pump is most efficient.

There are lesser pumps that advertise the gpm at 0 ft (0 psi) head without necessarily making that clear.

I added the red, and cropped off the top of the graph.

 

[AaronR]

View attachment 70024
If you seek out pump curves, you will see that if the head is low, that is the way they work. 25 gpm is not a max amount on a good pump, but rather the gpm where the pump is most efficient.

There are lesser pumps that advertise the gpm at 0 ft (0 psi) head without necessarily making that clear.

I added the red, and cropped off the top of the graph.

Great thanks for explaining that.

One last question should I size the CSV based on the pump rating or the actual flow (the 40gpm).

 

[Reach4]

I would think pump rating. You don't want your pump putting out 40 gpm much. But see what Valveman thinks.

Also think about the gpm that your emitters will consume.

 

[Valveman]

Even though a 25 GPM pump can supply more than 25 GPM as the pressure lowers, you will never use it that way unless you are just filling a pond. When you keep the 40-50 PSI on the pump needed to make the house and sprinklers working, that pump will only supply 25 GPM or less. 50 PSI is the same as adding 115' of head to the depth of the well.

 

[WorthFlorida]

I own an older home on 2/3 of an acre and I am working on redoing all the outdoor irrigation. I'm starting with trying to determine the flow rate of the well. .........Aaron

Redoing irrigation does that included pipe? If so Rainbird web site has a tool to layout the system. It'll give you a good idea on how many sprinklers needed. Highly recommend a WiFi controller, I have the Rainbird e-ESP but new models are now avaialble. With new pipe follow a simple rule, when using tees, always tee off with a smaller pipe. If you are using 3/4" feed, tee with a 3/4" x 1/2" x 3/4". Same if you are using 1" pipe. 1" x 3/4" (or 1/2") x 1" (or 3/4)". For servicing it is always easier to have all of the zone valves at one location, generally near the water source. You use more pipe but less wire. If the tees are before the zone valves then do use the same size tee for all directions.

With water conservation pressure just about everywhere, I recommend to use MP rotors by Hunter. Rain Bird's are called R-VAN. I have both but the Hunter is easier to adjust both distance and pattern. These are about the lowest rating per minute of water use other than drip. You may need more pop ups but there be hardly any overspray, fogging or run off. The watering time cycles are longer to allow time for the water to soak into the ground. With CSV it will be easier on the pump since there be no cycling especially with these MP rotors. Essentially you do not want too much water to the irrigation when in use otherwise your house needs will be greatly reduced when both call for water. I know this was not your question, just trying to help out.

 

[AaronR]

Redoing irrigation does that included pipe? If so Rainbird web site has a tool to layout the system. It'll give you a good idea on how many sprinklers needed. Highly recommend a WiFi controller, I have the Rainbird e-ESP but new models are now avaialble. With new pipe follow a simple rule, when using tees, always tee off with a smaller pipe. If you are using 3/4" feed, tee with a 3/4" x 1/2" x 3/4". Same if you are using 1" pipe. 1" x 3/4" (or 1/2") x 1" (or 3/4)". For servicing it is always easier to have all of the zone valves at one location, generally near the water source. You use more pipe but less wire. If the tees are before the zone valves then do use the same size tee for all directions.

With water conservation pressure just about everywhere, I recommend to use MP rotors by Hunter. Rain Bird's are called R-VAN. I have both but the Hunter is easier to adjust both distance and pattern. These are about the lowest rating per minute of water use other than drip. You may need more pop ups but there be hardly any overspray, fogging or run off. The watering time cycles are longer to allow time for the water to soak into the ground. With CSV it will be easier on the pump since there be no cycling especially with these MP rotors. Essentially you do not want too much water to the irrigation when in use otherwise your house needs will be greatly reduced when both call for water. I know this was not your question, just trying to help out.

Great info, thank you!

 

[2stupid2fixit]

I own an older home on 2/3 of an acre and I am working on redoing all the outdoor irrigation. I'm starting with trying to determine the flow rate of the well. I have a submersible pump with a 119 gallon pressure tank. I did a flow test utilizing a five gallon bucket and timing rate of fill as described on several websites. My pump did 20 gallons flat and then took 29.44 seconds for pressure tank to fill. This came out to roughly 40 gpm. Did I do something wrong seems way to high.
Thanks for some help.

Aaron

I am interested in the 5 gallon bucket test. Using a stopwatch and nothing else connected to restrict the flow, how much time does it take your well and pump setup to fill a 5 gallon bucket with cloud pudding?

 

[2stupid2fixit]

Even though a 25 GPM pump can supply more than 25 GPM as the pressure lowers, you will never use it that way unless you are just filling a pond. When you keep the 40-50 PSI on the pump needed to make the house and sprinklers working, that pump will only supply 25 GPM or less. 50 PSI is the same as adding 115' of head to the depth of the well.

i took your earlier advice, as these hallmark pumps are too cheap to not try. so i went back and i bought a 1 horse pump from them waiting for delivery (it was only $160 delivered).
When it gets a little warmer out i will yank up the 3/4 horse and inspect it then share photos and drop the 1 horse down in its place. The 3/4 horsey hallmark has been 200' down since october 2020. for sh&ts and grins i let the 3/4 horse run disconneceted to anything but poly to ground and it ran continuously for at least 6 and a half hours, when i came back the output flow was just as strong.