Pressure tank cycling with sprinkler recommendations

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H22lude

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I just had a FL22 pressure tank installed with a soda ash system pre pressure tank and two big blue filter housings post pressure tank (string and iron/manganese). From the pressure tank to the filters, the PEX is 1". From the big blue filters to the rest of the house the PEX is 3/4". And tee'd off the 3/4" PEX going to the house are the two spigots which are 1/2" PEX.

If I run one impact sprinkler off one spigot, the tank drains in 5 minutes 20 seconds (60 to 40). It takes 1 minutes 57 seconds to fill it back up (40 to 60), with the sprinkler on.

If I run two impact sprinklers, one at each spigot, it drains in 2 minutes and 40 seconds and fills up in 3 minutes and 24 seconds.

If I try to run two sprinklers from the same spigot, I get very low flow so it doesn't work. My guess is the 1/2" PEX is causing that problem. Luckily when the well company just installed the new FL22, they also installed a valve post pressure tank but pre big blue filters using 1" PEX that I can use to replumb the two spigots with bigger PEX. But that is another question for another day.

My question now is, which is better for the well pump? Taking longer to cycle on but short to cycle off, or somewhere in the middle where it cycles on a little quicker but cycles off a little longer.
 

Boycedrilling

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Ideally you don't want the pump to cycle at all while irrigating. It's not the running that wears out a motor, it's the starting.

You didn't mention what horsepower pump you have, and it's not that important for our discussion. Let's just say you have a 1 hp Grundfos pump and motor. Now I'm going to refer to the Grundfos Submersible Motor Guide. Comparable information can be found in other motor manufacturer 's manuals. Looking in the manual we see that a 1 hp 3 wire motor running at full load amps draws 9.0 amps and is 44.9% efficient. What does that tell us? Well of those 9 amps being used, only 4 amps are being converted to mechanical energy to rotate the pump. What happens to the other 5 amps? They have been converted to heat. Also when you start a pump it takes 4 to 6 times the full load amps to get the motor started rotating and up to speed. So now we're talking about 35 to 55 amps, and all almost all of that is being converted to heat. Remember only 4 amps are being converted to mechanical energy. So every time you start the motor you get a surge of energy that is mostly being converted to heat.

This is why every sub motor manufacturer publishes manuals that list the minimum run time of a motor along with max start per hour and day. Minimum flow rate or velocity of water past the motor for cooling flow. Also found is derating for elevated water temperatures.

Quoting from The Grundfos Manual, "Grundfos MS and MMS motors are designed for continuous or intermittent operation. Frequent motor starts can create excessive heat in the motor windings and negatively affect the life of the motor and other system components. Motor start draws more amperage than run. Higher amp draws make higher heat that can cause damage to motor windings or insulation"

For our hypothetical 1 hp motor, the motor start table list a maximum of 100 starts per hour and 300 per day. So Grundfos is indicating that you could start the motor as frequently as every 36 seconds for up to 60 minutes. However, on a continuous basis it should start no more than every 4 minutes and 48 seconds.

Your pump is cycling every 5 to 7 minutes. That is within Grundfos's specifications, if other criteria is also met.

However if it was me I would STRONGLY recommend that you install a Cycle Stop Valve to your system, if you are going to regularly use the outside spigots for any amount of time. Then the pump will not cycle as long as you are using at least 1 gallon per minute.
 

H22lude

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Great info, thanks! Only problem is I don't know what pump I have. I have the document when the well was drilled but nothing on it about pump. I can't make out the persons name that drilled it, but even I could, they probably don't keep records of what pump was installed 8 years ago. Is there an easy way to figure it out?

So it sounds like having just one sprinkler going and allowing the pump to rest for 5 minutes is the better option.

Before having the company install the FL22, I posted on here to get more info on what I should do. I was asking about the CSV but it didn't seem like it was the best option for my situation.

I'm wondering if I should install another spigot and run 3 sprinklers at once. This should keep the water running quicker than the pump can fill the pressure tank, which I would assume means the pump would continually run if all 3 sprinklers are running, correct?
 

Boycedrilling

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I live in an area that gets around 12 inches of precipitation per year. Irrigation water is essential to have a yard or garden. The typical farrmer here runs their irrigation system 2,000 hours per year
 

Valveman

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I just had a FL22 pressure tank installed with a soda ash system pre pressure tank and two big blue filter housings post pressure tank (string and iron/manganese). From the pressure tank to the filters, the PEX is 1". From the big blue filters to the rest of the house the PEX is 3/4". And tee'd off the 3/4" PEX going to the house are the two spigots which are 1/2" PEX.

If I run one impact sprinkler off one spigot, the tank drains in 5 minutes 20 seconds (60 to 40). It takes 1 minutes 57 seconds to fill it back up (40 to 60), with the sprinkler on.

If I run two impact sprinklers, one at each spigot, it drains in 2 minutes and 40 seconds and fills up in 3 minutes and 24 seconds.

If I try to run two sprinklers from the same spigot, I get very low flow so it doesn't work. My guess is the 1/2" PEX is causing that problem. Luckily when the well company just installed the new FL22, they also installed a valve post pressure tank but pre big blue filters using 1" PEX that I can use to replumb the two spigots with bigger PEX. But that is another question for another day.

My question now is, which is better for the well pump? Taking longer to cycle on but short to cycle off, or somewhere in the middle where it cycles on a little quicker but cycles off a little longer.

This means your sprinklers are using 4.1 GPM each and your pump is doing about 15 GPM. At 9.7 amps and 15 GPM I believe that is a 10 GPM, 1HP pump as a 7 GPM would pump about 12 GPM max. If it is a 10 GPM, 1HP, with a 20' static that would only be 164 PSI back pressure from a CSV, which is well within safe limits. You could test the back pressure with a gauge and a ball valve. You either need to add a CSV1A so the pump will not cycle while using 4.1, 8.2, or 12.3 GPM (1,2,or 3 sprinklers) or turn on a forth sprinkler for 16.4 GPM, which will keep the pump from cycling but cause low (weak) pressure because your pump only makes 15 GPM.

Even those 300 starts per day are a maximum number just to get the pump to last past its warranty date and no more. That is only 12.5 starts per hour, which is contradictory to their 100 starts per hour number, and is just crazy because a pump will not last long doing that.

This is a very true statement.
"Frequent motor starts can create excessive heat in the motor windings and negatively affect the life of the motor and other system components. Motor start draws more amperage than run. Higher amp draws make higher heat that can cause damage to motor windings or insulation"

Excessive cycling is what caused your problems in the first place. If you don't want the problems to be repeated, you will need to keep the pump from cycling on and off like that.
 

H22lude

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Is there a way to put the spigots on their own pressure tank with CSV using the same pump? I don't think I need a CSV for my house water with the FL22. Our normal water usage (minus outside water) is very low.

I could try out running 2 sprinklers at each spigot (4 total). The pressure and flow out of each would be lower but I could set them up so they water about the same area as 1. Or even look at getting different sprinklers that would work better in this situation.
 

Bannerman

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A CSV is to be located after the well pump but before the pressure tank.

A CSV would be beneficial regardless of the amount of water usually utilized. Small quantities of water drawn frequently will result in pump cycling which results in the problems you have experienced more so than drawing large amounts of water each pump cycle.

When the water being used is less than what the pump is delivering, a large pressure tank will not prevent cycling, but will provide longer pump run time once the pump has been activated. Because a CSV will change the way water is delivered from the pump, a large pressure tank will not be normally required but as you have just obtained a new tank, it may continue to be utilized with a CSV.
 

Ballvalve

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I simply turn my shut off pressure up to 75 PSI +/- and build my zones so that enough water is moving through the heads to not allow the pressure to reach 75. Rainbird makes a great 7$ impact sprinkler with 4 or 5 nozzles for flow control, so you can work it that way also. So the pressure tank is irrelevant. Polish or Slovak cycle stop valve. No internal parts, no cost.
 

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I simply turn my shut off pressure up to 75 PSI +/- and build my zones so that enough water is moving through the heads to not allow the pressure to reach 75. Rainbird makes a great 7$ impact sprinkler with 4 or 5 nozzles for flow control, so you can work it that way also. So the pressure tank is irrelevant. Polish or Slovak cycle stop valve. No internal parts, no cost.

Turning the pressure switch up to 75 works as long as your pump has a max pressure of 80-90 PSI. But most pumps will build more pressure than that, which means it is still pumping a lot of water at 75 PSI and will still cycle on and off. As has been said the CSV will be beneficial for your house as well as the sprinklers. The only problem is with an FL22 size tank you will have to use 22 gallons out of the tank as your feeling the pressure drop from 60 to 40. But as soon as the pump comes on the CSV will start holding a strong constant 55 PSI for as long as you are using water. Once you get use to the 55 PSI constant pressure you won't like having to wait for the tank to empty to feel it, but you can get use to it. It won't take long to understand the large tank was really not needed.
 

H22lude

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I think for now I'm just going to run one sprinkler at a time to keep the cycling under normal conditions. The pump cycles about 6 times over 45 minutes per sprinkler which is well below the 12.5 per hour. Granted this isn't the best situation but I feel it is a good middle ground for keeping the pump from cycling a lot and being able to water my grass a little. If I were to start watering more and look at inground sprinklers, I'd go with a CSV.
 

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If you had in ground sprinklers that were matched to the output of the pump you wouldn't need a CSV. But running fewer sprinklers and causing the pump to cycle on and off any is exactly what the CSV can fix. 12.5 cycles per hour is the number they give to get the pump to just last past the warranty date. There is a lot of difference between cycling 300 times a day and just 1 as it would be with the CSV.

Not only is the pump cycling 12.5 times per hour but the bladder in the tank is stretching all the way out and back in 12.5 times per hour, the pressure switch is sparking 12.5 times per hour, the check valve is slamming 12.5 times per hour, and the sprinklers go from squirting a big circle to only a little circle 12.5 times per hour. Might as well go out and start and shut off your car engine every 5 minutes as well. That big tank and slower cycle is just a false sense of security. I hear it all the time. "My pump only cycles every 5 minutes or so." That adds up to 300 cycles per day when you do the math. People just don't realize cycling on/off is what keeps the pump and tank companies profits up while needlessly draining the average persons savings.
 

Reach4

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I think for now I'm just going to run one sprinkler at a time to keep the cycling under normal conditions.
You would be better running 3 sprinklers at a time if you are able to run that other spigot.

You could try that by running a hose off of the drain valve for the pressure tank, perhaps out of a window if the tank is indoors.
 
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H22lude

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Yeah I could run a hose to my brewing sink in the basement. The filter guy put in a spigot after the big blue filters.
 

Bannerman

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It seems you are not recognizing the problem is using less water than the pump is supplying. Valveman calculated your pump is delivering 15 gpm, but 1 sprinkler is consuming only 4.1 gpm. Even if 3 sprinklers are running at the same time, that will be only 12.3 gpm which is still less than 15 gpm so the pump will continue to cycle.

A CSV will modify the output from the pump so the pump will only deliver flow equal to the water that is being used. You could then run that 4.1 gpm sprinkler 24/7 for the next 60 days and no cycling will occur.

If while the sprinkler is running you need a further 2.5 gpm to shower, then the CSV will immediately increase the flow rate from the pump to 6.6 gpm at the same consistent pressure. If someone also needed 3 gpm for washing laundry, the CSV will further increase the pump rate to 9.6 gpm delivered at the same consistent pressure as when only the single sprinkler was operating.

When a CSV is utilized, as long as at least 1 gpm is being consumed, the pump will not cycle.
 

H22lude

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No I completely understand that. Water usage needs to be more than the pump to keep the pump running.

I just emptied my tank and timed how long it took to fill up. FL22 at 40-60 has a 19.1 gallon capacity per the spec sheet. It took 82 seconds to fill up. That means the pump was pumping at 13.98gpm. I would need to run three 5gpm sprinklers to keep the pump running. That's not a big deal. Just need to install another spigot which I wanted to do anyway. Since the sprinklers are being used when we are sleeping, they will be the only things running.

My question though, and maybe I'm not understanding the CSV fully, is during normal daily life if you don't use a lot of water, how does the CSV and small tank benefit you over a larger tank? From the math side of it, it seems like the smaller tank with CSV would cycle more, not less. The CSV is only good when water is constantly running for a long time. Even with a washer machine running, HE ones only use 14 gallons per run. With a CSV and smaller tank, the pump would cycle on once. With a 20 gallon tank, it wouldn't cycle at all. Hell, even throw in a toilet flush, wash your hands and someone cleaning dishes for 5 minutes. With all that going on at once, the CSV would cycle the pump once and keep the water running until the water stopped then filled the tank while the larger tank would cycle the pump once and fill the tank back up. Both systems cycling the pump once. For the CSV and smaller tank to cycle less than a larger tank, I would think a lot of things would need to be using water. Maybe a washing machine with a shower going, someone flushing a toilet and washing their hands and then maybe even doing dishes or running the dishwasher. In that extreme case, I would say the CSV would be the better option. But to me, normal daily life, a larger tank would cycle much less...but maybe my exact situation is different than most. Maybe my wife and I use a lot less water than other houses.
 

H22lude

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The extreme case is watering your lawn.

Right, I get that. A CSV would be great for sprinklers OR just run more flow than the pump to keep it running. I'm questioning more daily life without sprinklers. Having a CSV for sprinklers is probably the best option but then it doesn't seem like a CSV would be good for daily life after sprinklers shut off (again, at least for me, my wife and son).
 

Reach4

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Mainly toilet flushing and quick showers would be the other extreme.
 

H22lude

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I guess that is what I'm getting at. CSV is good for people that use a lot of water consistently. Taking a 15 minute shower while other people are using toilets and sinks and maybe a dishwasher would be good for a CSV. But if you just take a shower with not much else going on or flush a toilet with a sink running for a few minutes, you'll never get the benefit of the CSV compared to a larger tank.
 
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