PDA

View Full Version : Determining GPM from a well pump


ArTurf
06-07-2012, 07:56 AM
What method do you like to use to determine your GPM from your water source? I do not have a flow meter. Does pump performance diminish over time due to worn impellers & etc? I do not work on many systems with supply from a well. There are hose bibs to work from.

Wet_Boots
06-07-2012, 08:07 AM
You get in the ballpark by way of the educated guess, knowing the pump horsepower and the usual "drawdown depth" of wells in the area.

ArTurf
06-07-2012, 10:38 AM
I realize now I did not explain the situation very well. I have a new customer whose system is on a well. At the end of last year the system began to lose pressure. When he fired it up this year the zones with a higher gpm would not even pop up due to lack of flow. Some of the smaller zones will work so-so but the lack of pressure is noticeable. At the beginning of this year he had someone install a new pressure tank.

I am going to take a gpm reading from a hose bib off the system using the 5 gallon bucket test. Does anyone have any better ideas?

I suppose pumps lose efficiency over time due to worn impellers & etc?

Wet_Boots
06-07-2012, 10:42 AM
It might be more likely to suspect a lower water table than a pump wearing down. I do believe a pump can lose effectiveness from worn internal components. Certainly, I've seen well installs lose performance over a year or two, prior to the pump getting replaced.

Mike Leary
06-07-2012, 11:14 AM
I am going to take a gpm reading from a hose bib off the system using the 5 gallon bucket test. Does anyone have any better ideas?

www.betterwaterind.com/flowmeter.html

ArTurf
06-07-2012, 12:30 PM
www.betterwaterind.com/flowmeter.html

Approx cost?

Wet_Boots
06-07-2012, 12:42 PM
If an existing system is now 'sick' you don't need flow-measurement tools, you need a well-water pro on the site.

Besides, there is a very easy way to use a homemade 'roofers square' and the water flowing from an open pipe to get a flow rate.

1idejim
06-07-2012, 01:13 PM
measure the flow close to the well head and before the tank. boots framing square method is accurate but is normally used in large diameter pipe low pressure situations, mainly in AG
Posted via Mobile Device

Wet_Boots
06-07-2012, 01:25 PM
Thing is, once the performance of an existing well starts to droop, there is little the sprinkler guy can do. You could re-nozzle heads to change the flow in a zone, but that is labor-intensive, and a waste of time and money, once the pump is replaced and the original performance restored.

jcsmith
06-07-2012, 01:39 PM
Last week I had a similar issue not enough pressure on all zones. All electrical measurements were acceptable. Pulled the pump and the galvanized male adapter on the pump discharge was corroded, almost broke off. Also earlier in the season had another system that some of the heads on all zones would not popup but the ones that did not popup could be pulled up and stayed up. It was almost a vacuum holding some of the heads down. Pulled the pump and the galvanized male adapter on the pump discharge had a hole in it.
Posted via Mobile Device

ArTurf
06-07-2012, 01:40 PM
Here are some other things I have found out. The pump is about 6 years old and is only used for irrigation on the lawn. It has performed OK until the end of last year. This year before starting up the system the pipe in the well was lowered about 5' due to the water table dropping in the area.

I capped off 4 heads on an 8 head zone and it performed well. Just guessing about 12gpm zone after cap off.

Mike Leary
06-07-2012, 02:17 PM
Here are some other things I have found out. The pump is about 6 years old and is only used for irrigation on the lawn. It has performed OK until the end of last year. This year before starting up the system the pipe in the well was lowered about 5' due to the water table dropping in the area.

I capped off 4 heads on an 8 head zone and it performed well. Just guessing about 12gpm zone after cap off.

Whomever did the work should have done a drawdown test and logged it.

Wet_Boots
06-07-2012, 02:21 PM
If the water table keep dropping, the level in the well will eventually fall to the pump itself, and the system will stop working.

Mike Leary
06-07-2012, 02:26 PM
Might be time to be thinking about a cistern or two to provide storage and pump from there.

ArTurf
06-07-2012, 02:28 PM
Whomever did the work should have done a drawdown test and logged it.

Very doubtful that happened.

Mike Leary
06-07-2012, 02:32 PM
Overzoning can cause the recharge rate to fail. I've been successfull using a clock with multiple programs and/or a zone delay to give the well some time to charge-up.

Mike Leary
06-07-2012, 03:20 PM
Approx cost?

They are not that bad for what they do, prolly $125.00 or so. I replace the psi gauge with a liquid-filled variety. You might be able to buy one on-line from the factory. Nothing against the ho-de-doe bucket tests or the "Clem" AG measurements, but this one is accurate, and short of a Data Industrial flow meter, they do fine for most applications.

greenmonster304
06-07-2012, 07:08 PM
This year I had a 5 hp sub lose about half it's output because of rust build up on the intake.
Posted via Mobile Device

Without A Drought
06-07-2012, 07:18 PM
i had 2 5hp 80 gpm well pumps changed last year due to decreased performance. will prolly get another one done this season

i have that flow gauge. it works well on higher flows/pressures, i dont use it in resi because under 15-20 gpm its had to get an accurate reading.

then again i don't do too much resi any more, and the commercial install is usually designed around pressure and safe flow rates

Mike Leary
06-07-2012, 07:51 PM
i dont use it in resi because under 15-20 gpm its had to get an accurate reading.

That's where that dweeb Toro flow/psi meter works best. Bootsville.

Wet_Boots
06-07-2012, 07:59 PM
That's where that dweeb Toro flow/psi meter works best. Bootsville.biteth me :realmad:

Mike Leary
06-07-2012, 08:20 PM
biteth me :realmad:

Hey! That's how we all started, untill it was realized to be a 30 psi max unit. :dizzy:

CAPT Stream Rotar
06-07-2012, 08:32 PM
I had centrifugal sh!t out on me the other day...SOB was primed, just way to old and no flow to go.

Without A Drought
06-09-2012, 12:34 PM
both have their disadvantages. in the higher flow commercials, it's not really necessary go get very accurate readings, as i rarely need maximum flow.
the resi is where it's a pain in the butt. around here i see flows as low as 7, and normally not higher than 15, from city water. a fudge factor of 3 or 5 can make a big difference in performance or material costs. most of the time i just take the flow gauge off the toro assembly and use a bucket.

Wet_Boots
06-09-2012, 12:44 PM
a Toro gauge set could be refitted to provide a higher range of flow readings, but why bother - it was created to use at homes with a 5/8 meter in the basement

Duekster
06-09-2012, 12:50 PM
Do you have the name plate info for the pump and motor or any start up data?

Centrifugal pumps do have wear rings and they do wear. This actually puts less load on the motor so the amp draw will decease.

May sound odd, but also check your voltages across the contactor Li and Lo . If the contactor is pitted, then there will be a voltage drop which will cause the motor to run hot and under less power and thus flow.

Wet_Boots
06-09-2012, 01:36 PM
Do you have the name plate info for the pump and motor or any start up data?

Centrifugal pumps do have wear rings and they do wear. This actually puts less load on the motor so the amp draw will decease.

May sound odd, but also check your voltages across the contactor Li and Lo . If the contactor is pitted, then there will be a voltage drop which will cause the motor to run hot and under less power and thus flow.I would be curious how long a power-robbing resistance could be present in any contacts before they simply burned up.

Duekster
06-09-2012, 01:45 PM
I would be curious how long a power-robbing resistance could be present in any contacts before they simply burned up.

Often the motor overloads will trip if it runs extensively. However it is the heat that breaks down the lacquer on the motor windings, then you get a shorted motor. Because pumps like this cycle, the heat slowly destroys the lacquer....and the pump may not trip on overload.

One other thing to look for is un-even voltages across legs. =/- 5% needs corrective action.

ArTurf
06-11-2012, 10:43 PM
Here is what I found out. I cut the pipe right after the pump and took a flow test using the bucket method with a pressure gauge with a ball valve to control pressure. Close to 30 gpm @ 40 psi. So I am thinking there is something going on between the pump and valves. It is a short run between the 2 so I began digging and hit a valve box that was previously unknown which contained a gate valve and then some type of ancient check valve. (The light bulb came on) So we cut them out and look in the gate valve and sure enough something had broken and the gate was halfway down. So we glue in a new ball valve and are giving it overnight to dry. Will go back tomorrow and check but I feel pretty confident this will cure it. The customer never knew the shut off valve was there as the box been overgrown with grass. He was happy we figured it out as he was thinking new pump or connecting to city water.

Duekster
06-12-2012, 07:13 AM
Sounds like you found the restriction Not going to replace the check?

ArTurf
06-12-2012, 07:50 AM
Sounds like you found the restriction Not going to replace the check?

The check was after the shut off valve and I assumed it was to protect the house supply from the water in the sprinkler system. The house is now on city water and the pump feeds the irrigation only. I didn't have a check on the truck and the owner was eager to get the system going. This is the only system I work on that works from a well. Should I put a check back on? Everything is still uncovered so it would make sense to do it now if it is necessary.

Dripit good
06-12-2012, 07:50 AM
So I am thinking there is something going on between the pump and valves. It is a short run between the 2 so I began digging and hit a valve box that was previously unknown which contained a gate valve and then some type of ancient check valve. (The light bulb came on) So we cut them out and look in the gate valve and sure enough something had broken and the gate was halfway down.

Great find. :clapping:

Kind of hard to understand how the gate valve next to the ancient check you found partially closed on it's own. No bf device between the pump and valves, or does the ancient check act as the protection?

Duekster
06-12-2012, 07:53 AM
Great find. :clapping:

Kind of hard to understand how the gate valve next to the ancient check you found partially closed on it's own. No bf device between the pump and valves, or does the ancient check act as the protection?
The stem rots, a little water hammer and the gate drops.

Dripit good
06-12-2012, 07:55 AM
This is the only system I work on that works from a well. Should I put a check back on? Everything is still uncovered so it would make sense to do it now if it is necessary.

I would consider eliminating the gate & check and installing a PVB in it's place.

Kiril
06-12-2012, 08:00 AM
Should I put a check back on? Everything is still uncovered so it would make sense to do it now if it is necessary.

Absolutely yes, and I would upgrade it to a PVB or RPZA.

Wet_Boots
06-12-2012, 08:09 AM
go all the way, and install a barometric loop

Sprinkus
06-12-2012, 08:15 AM
Barometric Loop. (http://www.gpta.net/Classes/07MethodsDevicesBackflowBackSiphonage/MethodsBackflow_files/page0007.htm)

http://www.backflowpreventiontechzone.com/barloop4.jpg

Duekster
06-12-2012, 08:22 AM
It is not connected to the house? If you do not have a foot valve on the pump, the purpose of the check could be to keep the irrigation lines from draining. Id the pump in the well submerged?

ArTurf
06-12-2012, 12:38 PM
The stem rots, a little water hammer and the gate drops.

Exactly what happened.

ArTurf
06-12-2012, 01:03 PM
I would consider eliminating the gate & check and installing a PVB in it's place.

Going with a ball valve for shut off purposes. Thought about a PVB but it would have to be mounted unusually high to keep it 12" above everything and it is a very visible area.

Am I correct that a backflow device is not absolutely necessary in this case? The system runs the irrigation only and stays constantly pressurized with a pressure tank. Lets assume there is a foot valve in the line somewhere beneath the ground. I'm not against backflow protection for the well, just wondering.

Wet_Boots
06-12-2012, 01:12 PM
Going with a ball valve for shut off purposes. Thought about a PVB but it would have to be mounted unusually high to keep it 12" above everything and it is a very visible area.

Am I correct that a backflow device is not absolutely necessary in this case? The system runs the irrigation only and stays constantly pressurized with a pressure tank. Lets assume there is a foot valve in the line somewhere beneath the ground. I'm not against backflow protection for the well, just wondering.Construction codes may require it, as it is considered potable water worthy of protection. One possible way to hedge your bets here is use some sort of check device/assembly with a pressure loss equal to a PVB or DCVA, so that the system is ready to work with one, if and when a retrofit is required.

Kiril
06-12-2012, 10:14 PM
Am I correct that a backflow device is not absolutely necessary in this case? The system runs the irrigation only and stays constantly pressurized with a pressure tank. Lets assume there is a foot valve in the line somewhere beneath the ground. I'm not against backflow protection for the well, just wondering.

Whether it is "required" or not, it is the responsible thing to do. Other people drink from that aquifer. :dizzy:

Duekster
06-13-2012, 06:36 AM
If code allows use a DCVA and it can be below grade.