How much PSI for 1.5HP Submersible?

[thegeeps20]

Greenhouse use. 1.5HP 15GPM Berkeley submersible pump 200' down installed last year. No control box or Amtrol tank, just turn on/off through breaker switch and water goes directly to garden hose.(I know, not optimal set up...lol) Currently has a 100 PSI relief valve installed on manifold at top off well casing.
We water our plants by standard hose, lengths run 250-300'. When watering with 1 hose only, the pressure will build up over 100PSI, so we usually run a second line into a holding tank and keep PSI around 90. Watering the plants with 1 hose at 90 PSI ,the pressure out of the 250-300' hose is really good for our needs, but we would like to know if we could go higher on the PSI and not have to run a second line to lower pressure below 100 PSI.
First question, I assume running at 90 PSI is ok? Secondly, how high on the PSI can we actually go to not do damage to the pump? If we can run higher PSI, I would set relief valve higher, or get a new one.
Last question, when a relief valve is triggered, can it still be used? I ask because the valve was working last year, but I recently had PSI go over 100 and the valve did not open.
Any input appreciated, thanks.

edit: pump manual states this:
Shut off head: feet-403, PSI 174. Is this relevant to my questions?

 

[FishScreener]

What is the Pump curve? it tells you everything about the pump, and where it should be run, if you know how to read them. Pump manufacturers have explanations of them on their websites. It should be in the paperwork which came with the pump.

Simplest, and least expensive, solution is probably to add a properly sized well tank, and pressure switch. The tank manufacturers have calculators online, which will help you size the tank, to prevent damage to the pump. The pump needs to run for several minutes when it comes on, and then have about twice that long to dissipate heat before it turns back on. The tank keeps you in the 20-psi pressure range. Idealy the pressure range of the pressure switch matches the pump curve, and keeps things in the pumps highest efficiency range.

 

[thegeeps20]

What is the Pump curve? it tells you everything about the pump, and where it should be run, if you know how to read them. Pump manufacturers have explanations of them on their websites. It should be in the paperwork which came with the pump.

Simplest, and least expensive, solution is probably to add a properly sized well tank, and pressure switch. The tank manufacturers have calculators online, which will help you size the tank, to prevent damage to the pump. The pump needs to run for several minutes when it comes on, and then have about twice that long to dissipate heat before it turns back on. The tank keeps you in the 20-psi pressure range. Idealy the pressure range of the pressure switch matches the pump curve, and keeps things in the pumps highest efficiency range.

thanks for the reply. At this point, there won't be a tank installed. We made that decision based on simplicity, meaning well location compared to were a tank would need to be installed. When the pump is turned on, it runs for hours while we are irrigating our plants.
Our submersibles have always run 4-6 hours straight when turned on(every day for months and have lasted for years(7-10 usually, rust build up is usually the problem )
The pump curve lists PSI from 0-80, does that mean the pump can't be run at a higher PSI? I thought that would be more of a concern with plumbing fixtures, valves, ect. Would running any higher damage the pump, that is my main concern?

15GPM, 1.5HP
https://www.pentair.com/content/dam...eley/spec-sheets/jp-series-specifications.pdf

 

[Valveman]

It depends on how deep the water is in your 200' deep well. That pump can still make 100 PSI even if the water level is at 170'. But if the water level is at 10', that pump will make 170 PSI at the surface. Not even 170 PSI will hurt the pump, as long as it is still pumping at least 1 GPM. So, you can have as much pressure as you want.

However, controlling with a pressure relief valve is not good. They are made for emergencies only and will quit working if used too many times. They will either fail to open or fail to close.

Using a CSV1A on the pump set for 100 PSI and installing the pressure relief valve after the CSV1A, the pressure relief would only be needed if you left the pump on and was using less than 1 GPM. This would give you 100 PSI constant on the hose and make your pressure relief valve be used for protection only.

Adding a 10 gallon pressure tank and a 90/110 pressure switch, as in a PK1A kit, would give the same strong constant pressure and be completely automatic. This way you just turn a faucet on when you want 100 PSI on a hole and the system will come on when needed and go off when not. No more need to make sure and turn the pump off when you are finished watering, just turn off the faucet to the hose.

 

[thegeeps20]

thanks for your suggestions, will look into. We don't control with the relief valve, we just tweak the shut off valves for the hoses to increase/decrease the PSI. The static water level is about 57' and after running for 6 hours water is down to 127'. Well is actually 400' with pump set at 200'

 

[MicEd69]

Thegeeps20, the flow and pressure from your pumps is determined on where the system curve intersects the pump curve. The system curve is based on the layout and geometry of your piping system. Both curves are usually expressed in terms of feet of head; approximately 2.3 feet of water is 1 psi. The system curve obviously has zero flow at zero feet of head, and flow increases when more head is supplied to the system. I’ve approximated a couple of system curves below.

What you have stated is that you have to increase flow from the pump through a second hose to keep from going over 90 psi, which is equivalent to ~207 feet of head at grade. At the start of your pumping, the pump also has to overcome the static head of 57 feet. Now when you increase flow by opening the second hose, you change your system curve down to 264 feet, (207 + 57), which according to your pump curve is around 14 gpm. That is the red system curve below. That means that the system curve for your system without the second hose flowing hits the pump curve to the left of the 264 foot head point of your pump.

You didn’t state what the flow rate is through the second hose to your holding tank, but let’s assume it is a good 20% of your flow, or ~3 gpm. With these assumptions, the blue system curve approximates the system curve you would have without the second hose flowing. When starting pumping, the head required would be ~315 feet. That total head, less the static head of 57 feet, leaves you with a head of 258 feet at grade or around 112 psi.

The pump curve shows a “recommended” minimum flow of around 7.5 GPM at which the pump will develop a head of 350 feet. For your system with a minimum static head of 57 feet, the head at grade would be 293 feet, or 127 psi.

The manufacturer recommends a 100 psi relief valve if a Pro-Source Series pressure tank is used as that is the maximum operating pressure of that tank. However, operating the pump at the higher pressures above will not hurt the pump as long as the flow from the pump is continuous. The pump curve is what the pump is guaranteed to do, so operating any place along that curve is acceptable. The dashed lines at the lower and higher flow rates are areas that the pump should not be operated.

There could be a mild concern with some of your other system components. Some normal water components are rated for only 125 psi. But I take it this is more of a commercial installation, so your piping system may have industrial type components. And I would assume the 250’-300’ hoses are heavy duty hoses.

If you do decide to increase the relief valve on the pump head to something like 125 psi so you can operate at a normal 112 psi, just be sure everyone knows not to close any valves until the pump is turned off. Get a quality glycerin filled pressure gauge to monitor the pump pressure, and a high-quality relief valve. As others have said, the relief valve is not supposed to work unless there is an abnormal situation.

And also, as others have said, a pressure tank with a switch to operate the pump is the classic way to go. But provided your distribution system has adequate pressure rated components, this would work.

 

[thegeeps20]

thanks for your detailed reply, very informative. Are you saying the PSI without the second line should be 112 or 127?

 

[MicEd69]

Assuming the system curves are close, without using the second hose, the pressure would be 112 psi at the start of your watering. At the end of your watering as your static head goes up to 127 feet, the pressure at the well head would be around 82 psi. The drop in pressure is due to the increased static head the pump has to overcome. You do notice that now, don't you?

The 127 psi is what the minimum "recommended" flow of the pump will provide assuming the static head is 57 feet.

If you want to provide a few flow rates of each hose, the corresponding pressure at the well head, and the level in the well (assuming you can do all that at the same time), a better system curve could be developed. But based on what you've proved, I'm thinking this would be a workable system with normal maximum working pressure of ~112 psi and a relief valve at 125 psi.

 

[thegeeps20]

from my notes when pump was installed:
after 1 hour, 2 hoses producing 8 GPM each
after 6 hours, water level in well at 127' running 2 hoses, gauge reads 50 PSI

The problem in my area is iron and after a few years rust build up on intake of pump and slowly clogs impellers so pump performance diminishes over time. This set up is on a new well dug last year and the rust seems to be a lot less than previous well.

Edit-Static water level is 48'

 

[MicEd69]

Yep, that seems reasonable. The static water at 48 feet will increase the pressure around 4 psi to 116 psi, but the pressure will drop from there as the stsatic head increases, so this approach should still be quite reasonably.

 

[Valveman]

Most smaller systems do not have a system curve. If you need 100 PSI or 50 PSI, you still need the same pressure if running one hose or two. When I see someone mention a "system curve" I am afraid they are going to start talking about how a variable speed pump can save energy. No matter the system curve, a VFD always uses more energy per gallon, not less. But a lot of people want to falsely believe that slowing a pump down to match a system curve will save energy. A system curve is not very useful unless sometimes you use water at 100 PSI and other times you only need 50 PSI, which is rare.

A Cycle Stop Valve tries to maintain a set constant pressure like 100 PSI. Regardless of what the dotted line on the curve says, that pump and most 2HP or smaller submersibles can safely run as low as 1 GPM continuously. But if you open up two hoses, the pump is not large enough to keep the pressure at 100 PSI, and the CSV will open up and give you 50 PSI, which is all the pump can produce. With the CSV you just don't have to run two hoses, as the CSV will let the pump stay running down to as little as 1 GPM.

With a water level at 127', that pump can only build 118 PSI. Setting a pressure relief valve any higher than about 115 PSI could cause the pump to dead head and melt down. Setting the CSV1A to 100 PSI, you can install a pressure relief after the CSV set at 110 PSI. If you forget to shut the pump off and all the taps are closed, the 1 GPM coming through the CSV will be all that the pressure relief valve has left to dump when the pressure gets up to 110 PSI, which will still keep the pump cool and happy.

As for the iron...
You can use a little larger pressure tank with the CSV like a 44 gallon size that holds 10 gallons of water. Attaching a Sulfur Eliminator to a hose and dropping it down the well will put 1.5 gallons per hour of aerated water down the well. Aerating the water in the well should keep the iron from building up on the pump screen. The larger tank is needed even with a CSV when there is a continuous demand for small amounts of water like the Sulfur Eliminator uses.

 

[MicEd69]

Most smaller systems do not have a system curve. If you need 100 PSI or 50 PSI, you still need the same pressure if running one hose or two. When I see someone mention a "system curve" I am afraid they are going to start talking about how a variable speed pump can save energy. No matter the system curve, a VFD always uses more energy per gallon, not less. But a lot of people want to falsely believe that slowing a pump down to match a system curve will save energy. A system curve is not very useful unless sometimes you use water at 100 PSI and other times you only need 50 PSI, which is rare.

A Cycle Stop Valve tries to maintain a set constant pressure like 100 PSI. Regardless of what the dotted line on the curve says, that pump and most 2HP or smaller submersibles can safely run as low as 1 GPM continuously. But if you open up two hoses, the pump is not large enough to keep the pressure at 100 PSI, and the CSV will open up and give you 50 PSI, which is all the pump can produce. With the CSV you just don't have to run two hoses, as the CSV will let the pump stay running down to as little as 1 GPM.

With a water level at 127', that pump can only build 118 PSI. Setting a pressure relief valve any higher than about 115 PSI could cause the pump to dead head and melt down. Setting the CSV1A to 100 PSI, you can install a pressure relief after the CSV set at 110 PSI. If you forget to shut the pump off and all the taps are closed, the 1 GPM coming through the CSV will be all that the pressure relief valve has left to dump when the pressure gets up to 110 PSI, which will still keep the pump cool and happy.

As for the iron...
You can use a little larger pressure tank with the CSV like a 44 gallon size that holds 10 gallons of water. Attaching a Sulfur Eliminator to a hose and dropping it down the well will put 1.5 gallons per hour of aerated water down the well. Aerating the water in the well should keep the iron from building up on the pump screen. The larger tank is needed even with a CSV when there is a continuous demand for small amounts of water like the Sulfur Eliminator uses.

As a pump controls tech, I am very surprised that you say, “Most smaller systems do not have a system curve.” EVERY piping system has a “system curve” by definition. A CSV mechanically modifies the piping system and thereby changes the “system curve” in which it is installed. It changes it such that the “system curve” intersects the pump curve at a point to match the setpoint of the CSV.

And perhaps you did not read the initial post. Thegeeps20 is using this system for greenhouse watering, and it has no tank or pressure control system whatsoever. Everything is being done manually. The pump is actually turned on and off by flipping the breaker to the pump. Can’t get much simpler than that. There are tons of such super simple systems in the United States, largely in rural places.

While I have used VFDs in numerous industrial projects, in no way would I be thinking those would be an answer here. Nor would I recommend a CSV here for other reasons. A CVS is a mechanical device with moving part, which due to the iron in the water will end up being a maintenance issue. Thegeeps20, nor the watered plants, appear to be concerned about the iron in the water. Thegeeps20 seems to have provided that tidbit of information as a comment on the required frequency of pump replacement, and that their new well appears to have less iron.

Bottom line is that Thegeeps20 does not want an instrumented system, but just wants to know the workability of this super simple system at higher pressures if only one hose is being used. And that is the answer that I provided.

 

[Valveman]

No offense intended. Maybe I should have said a system curve is a moot point when the well is always 127' to water and you need 50 PSI if running one hose or several. A system will need 242' of head all the time to accomplish that.

You can use a Cycle Stop Valve without a pressure tank or pressure switch and it will hold whatever pressure you set it, as long as the pump can keep up. No more need to dump excess water to maintain pressure. The CSV will not clog up with iron any more than the pump screen or check valve.

Using the pressure tank with a pressure switch is a way to provide water to the Sulfur Eliminator during the time no other water is being used, In that way the water in the well will be clean, the pump screen nor anything else will clog with iron, which will solve the short lived pump problem.

You can also add a Cycle Sensor which will shut the pump off on low amps if/when the screen becomes clogged, which will also save the pump.

 

[MicEd69]

There you go, much better put.

And if Thegeeps20 wants to add additional parts to his system, rather than running the system at a higher pressure with varied flows as the well static head changes, (which was his original question), the approaches you suggested would be things he could do. But he has stated, "At this point, there won't be a tank installed. We made that decision based on simplicity, meaning well location compared to where a tank would need to be installed."

I'm sure if this was well water being used for his home, his system would look a lot different. But as the water is solely used for greenhouse watering of plants, and as the pump is turned on by flipping the breaker with no switch at the pump, and as the pump "always run 4-6 hours straight when turned on... every day for months...", it might just be that he wants the system to be as simple as absolutely possible. Cycling of the pump and varied pressure to his hoses is not a concern here.

It's great to provide options for improved systems to people asking questions, so I'm sure he appreciates your input should he decide to install a more "standard" well pump system in the future.

 

[Valveman]

I agree, but is simplicity based on the number of components or on function? Adding a pressure tank/pressure switch and even a Cycle Stop Valve is not adding many components and is still a simple system. The pressure switch and tank just remove one more possibility for an operator error. And since making the pump last longer is the goal, making sure it shuts off if someone closes all the taps can be important. The pump could be destroyed by the screen clogging with iron. But it could also be destroyed if someone forgot to flip the breaker off. As a pump installer I prefer the systems to be fool proof. I can't remember where I put my glasses, much less to turn off the breaker every time I am finished using water.

Oh an BTW. The main reason I mentioned a pressure tank was to supply the Sulfur Eliminator, which might also help keep the pump screen clean and make the pump last longer.

 

[MicEd69]

Yep, I agree. I was just going by what Thegeeps20 said about adding a pressure tank wasn't an option based on where the pressure tank would have to be located. I don't fully understand that statement, but I'm taking it as a fact.

On my grandfather's dairy farm, his well only provided water for the cows. The pump was turned on to fill the watering troughs by throwing a fused disconnect switch. Yes, the tanks would overflow at times, but there were no valves in the piping whatsoever. I'm thinking it is very likely that the system Thegeeps20 has is also free of any valves.

His simple system has apparently lasted over 20 years, since he indicates the pumps last 7-10 years, and as such he must have replaced it at least twice. So, the bottom line is that operating this new well at a pressure higher than 100 psi should not be an issue based on the pump he has and the fact he does not require pressure or flow control for watering his plants.

This is not system that you would likely find supplying water to a house, but for agricultural use, there's a ton in rural United States.

 

[Valveman]

Yep, I agree. I was just going by what Thegeeps20 said about adding a pressure tank wasn't an option based on where the pressure tank would have to be located. I don't fully understand that statement, but I'm taking it as a fact.

That was another reason I mentioned the CSV system. Even at 90/110 pressure he could use as little as a 10 gallon size tank. The tank and pressure switch can also be installed hundreds of feet away from the CSV if needed. The little tanks we use have a 150 PSI rating and don't take up much space, which might work since it is a much smaller pressure tank?

But yeah a lot of pumps can just be turned on when needed. Most irrigation pumps in the cotton fields around me just have an on button. They are usually running 3-4 months at a time or not at all. I have a stock water well pump that only has a breaker as control, as it hasn't been turned off in over 21 years so far. Pumps are made to run continuously anyway.

 

[thegeeps20]

Assuming the system curves are close, without using the second hose, the pressure would be 112 psi at the start of your watering. At the end of your watering as your static head goes up to 127 feet, the pressure at the well head would be around 82 psi. The drop in pressure is due to the increased static head the pump has to overcome. You do notice that now, don't you?

The 127 psi is what the minimum "recommended" flow of the pump will provide assuming the static head is 57 feet.

If you want to provide a few flow rates of each hose, the corresponding pressure at the well head, and the level in the well (assuming you can do all that at the same time), a better system curve could be developed. But based on what you've proved, I'm thinking this would be a workable system with normal maximum working pressure of ~112 psi and a relief valve at 125 psi.

I just installed a new pressure gauge(glycerol and stainless) and adjusted relief valve to 125PSI. It appears the pump has maybe lost some effectiveness from last year or the static water level may be lower now. Running a 350' hose line, the PSI was about 110 at start up, but went down to 90 PSI after running 20 minutes or so. The GPM coming from the end of the hose was exactly 12. What do you think?
I was told the well was producing(recovery) 13GPM when dug last year, but not sure if it was measured correctly. If correct, using 12GPM while watering, shouldn't the static level remain about the same?

 

[Valveman]

The GPM coming out of the hose should be less when the pressure is at 90 than when at 110 PSI. Regardless of that, it is common for the pumping level to be lower than the static level. Some really strong wells have the same static and pumping levels. But I would expect a well that can make 13 GPM to draw the level down considerably while using 12 GPM.

Your pump may not be able to build 125 PSI for the pressure relief valve to work if someone closes the hose when the well is pulled down and only delivering 90 PSI. But with the hose closed the pumping level should quickly rise to the static level, and the pressure relief will again be able to pop off at 125 PSI and protect the pump from dead heading.

 

[thegeeps20]

The GPM coming out of the hose should be less when the pressure is at 90 than when at 110 PSI. Regardless of that, it is common for the pumping level to be lower than the static level. Some really strong wells have the same static and pumping levels. But I would expect a well that can make 13 GPM to draw the level down considerably while using 12 GPM.

Your pump may not be able to build 125 PSI for the pressure relief valve to work if someone closes the hose when the well is pulled down and only delivering 90 PSI. But with the hose closed the pumping level should quickly rise to the static level, and the pressure relief will again be able to pop off at 125 PSI and protect the pump from dead heading.

thanks for the reply. Maybe I have a mental block, but if the well is recovering at 13GPM and I'm only drawing 12GPM, shouldn't the well level in the well remain about the same?