“Your pump isn’t producing enough flow!”
“I can’t get enough pressure out of your pump!”
“Your pump is making noise!”

We often get these calls from the field.  While it is entirely possible, in reality, it is rarely the pump’s fault.

From my almost fifty years of field experience with pump troubleshooting; I’ve found almost 80 percent of all centrifugal pump issues are on the suction side of the pump. I always start looking there first.

Key Data Needed, Prior to Calling Factory or RSM:

  • Pump serial number.
  • Fluid properties, or as I like to call it the “fluid personality”. (Temperature / Vapor Pressure / Specific Gravity / Viscosity / Suspended Solids / pH 
  • What condition was the pump sized for? Flow and head (differential head)
  • What clearance is the impeller set at? 
  • What is the Shutoff pressure?
  • Duty Cycle
  • NPSHA?
  • Submergence?
  • Is the pump suction condition in a lift or flooded situation?
  • Perhaps supply a sketch or photos of the system showing pipe size, elevations and components.  “A picture is worth a thousand words”
  • New application or replacement?  If it’s a replacement pump, ask why they are replacing it.

The above data should be fairly quick and easy to get from the customer, using a Summit Pump Application Data Sheet. If you cannot solve the problem based on the above data, below are some more in-depth items to investigate further:

Sketch your pump’s performance against the Summit Pump performance curve.


Further Investigation:

  1. Confirm pump speed (RPM). This can be done with a tachometer.  Be on the lookout for VFD issues, belt or engine driven installations.
  2. Confirm direction of rotation.
  3. Proper suction piping per ANSI/HI 9.6.6 guidelines.  Proper pipe diameter, length and orientation is critical to successful pump/system operation
  4. Check the suction source.  Is the tank too small, causing turbulence and high velocity? Is there entrained air in the liquid? Is there proper submergence?
  5. Gauges. Are the proper gauges installed?  Are they calibrated?
  6. Suction lift conditions.  Is the lift too high?  What is the vapor pressure? Air leaks?
  7. Head & NPSHa Calculations.  Confirm the head & NPSHa calculations.  What is the NPSH margin? If the calculations are incorrect, the pump could be incorrectly sized for the application.
  8. Confirm liquid properties.  Is the given information actually the liquid they are pumping?  Did the process liquid change?  (Specific Gravity, Viscosity, Temperature, Vapor Pressure)
  9. Pipe Strain. Is the piping properly supported? If not, pipe strain will usually manifest as hot bearings and alignment related issues. Was it laser-aligned?
  10. Parallel or Series Pumping.  If not installed/operated correctly, pumps operating in parallel or series can have problems, and the pump(s) might not perform correctly.

Next Steps:

If you don’t know how to investigate these issues, and/or you are simply not comfortable with the process, we can assist, but please know that we are not system designers.


We fully understand that when the pump is misbehaving and cranky the customer is pointing at you and directing unpleasant pressure to fix the issue immediately. Your best friends in this situation are pump/system knowledge, experience and the IOM; so we strongly recommend you (and your customer) read and understand the IOM before starting the pump.

Last, but most assuredly not least, the Summit Pump staff are here to assist.

-The Summit Pump Team

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Jim Elsey's Pumps and Systems Articles

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products in a timely manner,
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 No one specific subject or theme this month, just a random collection of tips.
Kind of like the junk drawer in my desk. 

Pop Quiz: What pump company made the first ANSI (B73.1) Pump?
Answer at the end.


You’re Grounded:
If electric arc welding near the pump, be certain a solid ground is installed near the welding area and away from the pump. Otherwise arcing may occur inside the pump at the close clearances. This can cause damage to the pump, especially in the bearings and possibly cause failure.

Don’t forget that VFD drives are notorious for inducing stray currents into the motor that can travel to the pump and create bearing damage. Make sure the equipment is grounded.


“Gauges!?…We don’t need no stinking’ gauges!”: 
Would you drive a car without a dash board? Then why have a pump with no suction or discharge gages?
Without gages you have NO clue as to where the pump is on the curve. Push back on your customer to have gages installed, or at least make allowances for their installation when required.

Remember the gage readings will have to be corrected for elevation differences above or below the pump, since the reference plane for total head is the impeller centerline in most all cases.


Bearings; relative or otherwise:
On a single stage end suction pump the expected bearing life will typically increase with an increase in suction pressure and decrease with lower suction pressure.

Shaft kits and rotors should be rotated by hand at least once a quarter to mitigate the effects of false brinelling. Ball bearings, not in service, even when sitting in the storeroom on the shelf can be subjected to false brinelling. Make sure they have a protective coating to prevent corrosion even in climate controlled surroundings.



Summit Pump does NOT manufacture pumps to NSF61 specifications. Please be aware that some water systems for potable use or swimming pools for public use may require this certification.

NSF require companies to comply with the strict standards and its product certification programs. More information at their website: http://www.nsf.org/services/by-industry/water-wastewater/municipal-water-treatment/nsf-ansi-can-standard-61


Answer: Dean Brothers introduced the first ANSI pump in 1958. They introduced their model PH and the ASA (American Standards Association) recognized the pump as their standard, and then the MCA (Manufacturing Chemist Association) adopted the pump as the AVS (American Voluntary Standard) then the ANSI (American National Standards Institute) approved the AVS standards as their own with the designation B123.1

This standard was later revised and approved as ANSI B73.1

– The Summit Pump Team

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Several times a month we receive an inquiry from a concerned customer that the “stainless steel” they received from Summit Pump is magnetic and/or appears to be rusting.
We assure them there is no issue, and explain as follows. 


In the case of plain/standard 316-SS, it is usually because the piece has been cold worked and will pick up some magnetic properties. Note if you were to compare the 316-SS to a 400 series stainless you would see an increase in magnitude of the magnetic attraction. It will not attract other ferritic metals, only the magnet, as a result the material itself is not necessarily magnetic, it is ferrous. The magnetic response has no effect on any other property. Austenitic 300 series steels like cold drawn 304 (and to a lesser degree 316) are slightly attracted to a magnet, but this has no effect on its corrosion resistance.


Cold Working: Parts that are highly worked (due to machine operations), such as sleeves and shafts that have been machined, ground and polished, will lend themselves even more to this phenomena.

Corrosion: In 316-SS it is the chrome content that makes it stainless, but it is the nickel content that makes it nonmagnetic.

In the process of cleaning the materials at the foundry and the machine shop, there could be some residual ferrite (iron) from the cleaning process which temporarily alters the surface.  The surface may become contaminated on the work site as well. The remedy is to pickle and passivate the surface once again. Stainless surfaces must be kept clean, so the surface can generate the passivation layer and remain as new. It is the chrome oxide film that stainless naturally forms that keeps it from corroding.


Rolled or Cast: There is a difference in cast stainless steels versus wrought stainless steels that aggravates and differentiates the issue of magnetic attraction. In the case of cast stainless steel, like CF8M, the chemistry and micro structure are purposely different from rolled steel, but the physical and corrosion properties are similar. AISI 316-SS is wrought steel and is notably less or nonmagnetic altogether, as compared to CF8M.



We want some ferrite in the CF8M cast steels to increase the strength and increase its resistance to corrosion cracking. The small amount of ferrite also reduces some forms of corrosion and helps with weldability.

Duplex and Super Duplex Materials: CD4MCu is a duplex stainless steel with magnetic attraction, due to its ferrite content.

If you remain concerned about the material’s magnetic properties, please discuss with engineering or your RSM. It’s possible to perform and document a witnessed PMI test at no charge.

– The Summit Pump Team

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What is slip? How does it affect
Positive Displacement Pump performance?

Is Your Pump Slipping?

Fluid slip is a common term used to describe reverse fluid flow inside a pump or other turbomachinery. Slip is affected by internal clearances of the parts, temperature, pressure and viscosity.

In a positive displacement pump, slip can be easily calculated just by looking at the flow being produced while in operation and subtracted from the nominal flow rate of the pump per one revolution.

Another way to determine the amount of slip is looking at the pump curve. At 0 psi, the pump is producing its nominal flow at the RPM. Notice as the pressure increases running at the same RPM, the flow will decrease. The difference between the operating pressure and 0 psi is the amount of fluid slip the pump is experiencing. This method is more of an approximation whereas the above measured flow minus the nominal flow per revolution is more accurate.


Why Should we Care About Slip?

Most importantly, too much slip can increase wear and decrease pump life, especially if the fluid is abrasive or has solids. Abrasive fluid passing through the clearances of the internal parts has the same effect of sand blasting. This opens up the clearances even more, amplifying the issue.

Next, too much slip can increase the cost of operation and loss of efficiency. In a positive displacement pump, if you are not getting the desired flow rate the first thing you do is turn up the speed, but doing this also increases the required power needed to meet same flow and pressure.


Excessive amounts of slip will introduce heat into the pump. This is critical in both the Progressive Cavity and Internal Gear Pump lines. Elastomers in the Progressive Cavity’s stator, or any rubber, has a set life limit based on how much heat it can absorb.  The more heat it absorbs, the shorter its life.

The clearances in the Internal Gear Pump are extremely tight and with extra heat introduced can cause the rotor and idler to expand and potentially lock up against the head or casing.  As a side note, if the safety relief valve is being used as a flow throttling mechanism, it can also cause the rotor and idler to expand as well.


How do you Decrease Slip?

When sizing positive displacement pumps, our guidelines is to keep slip under 15% of the desired flow rate.  One option to achieve this is to choose a smaller pump, but keep in mind RPM restrictions. When sizing Progressive Cavity pumps, our guideline is nothing faster than 300 RPM, to minimize the amount of heat generated to maximize stator elastomer life.


“Summit Pump Man, 
I don’t want to change my existing pump size, what else can I do to minimize slip?”

Reduce the pressure of the system. Reduce the all unnecessary fittings, increase pipe diameter, operate at a lower flow rate, ensure all filters and pipe runs are clean of debris, shorten the distance the fluid has to run.

A convenient feature of the Progressive Cavity pump is the ability to simply change the stage of the pump. For example, increasing a 2-stage rotor and stator to a 4-stage will reduce the amount of pressure per stage the pump experiences. Ultimately, reducing the amount of slip by a factor of the stage change. As with everything, there is always a tradeoff, torque and power required will increase and resulting factors need to be examined, such as motor size, pump frame size and location space available.

Click to Enlarge

– The Summit Pump Team

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Baseplates: Flat and Level

Pump Alignments
We all know that proper alignments between the pump and the driver are critical. Did you know that the bearing load increases in direct proportion with the misalignment? But even more importantly, a bearing load increase will decrease the bearing life by a cubic function. Simply stated, if the bearing load increases by a factor of two, due to misalignment, then the bearing life decreases by a factor of eight.

Warning: All pumps must be final aligned in the field. No matter how precise the alignment from the factory, it will be lost when the unit is shipped and installed.

Baseplates: Flat and Level
Baseplate flatness has become an issue in recent years as customers are looking to simplify installation and alignment and reduce MTBF (mean time between failures), while attempting to also reduce costs.

Most of us understand that the pump baseplate has to be level. The biggest reason for that criterion is the oil level in the bearing housing. It is possible to have too much oil on one bearing (for example the radial bearing) and not enough on the other bearing (thrust bearing). If the proper oil level is the middle of the bottom ball then it doesn’t take a whole lot of “being un-level” to miss this crucial mark.

What is flat?
A typical fabricated steel baseplate for an ANSI or standard industrial pump will be flat to within 0.005 inches (0.127 millimeters) per foot (0.3048 meter).

Example: If the distance between the pump mounting pad and the motor mounting pad is 4 feet (1.2192 meters), then the motor pad can be 0.020 inches (0.508 millimeters) higher or lower than the pump pad. If a pump pad is one foot (0.3048 meter) long, it can be 0.005 inches (0.127 millimeters) lower or higher on one end.

Process Industries Practices (PIP) (and API610) bases for the same model can be 0.002 inches (0.0508 millimeters) per foot (0.3048 meter), or less than half of the standard baseplate.

A flat surface will allow the installer to more effectively level the baseplate prior to grouting and then align the motor to the pump by shimming under the motor feet. When attempting to align the pump and motor shaft to within 0.002 inches (0.0508 millimeters) TIR (Total Indicator Run-out), it is easier to start out on a level playing field rather than have unequal shim stacks under each foot of the motor.Extra Credit:

Good millwrights and pump technicians/mechanics know to check for *soft-foot before they start the pump to driver alignment.

*“soft-foot” is where one or more feet are not in contact with the mounting pad when the unit is in the unbolted condition (this should be corrected by shimming, not by tightening the bolt which may distort the motor frame).

If you had a soft-foot of 0.016” and then bolted the motor down anyway; you have just introduced 0.008” of strain/stress into the driver. There is now potentially 0.008” of offset between the front and rear bearings, regardless of the motor size. If you do a similar offset to the pump, again you have introduced an internal stress on the bearings and shaft. Even without soft-foot on either pump or motor, if the baseplate is not flat, you have just done the same thing to the driver and or motor. Bases must be level and flat.

– The Summit Pump Team

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Truth: Pumps Shipped From the Factory are NOT Ready
to be Started and Operated

Once a year I attempt to remind all Summit Pump distributors of the “Plug and Play” myths that unfortunately persist in the pump universe, like fake moon landings and that the earth is flat.

Please make sure you and others on your staff know these 5 key points:
1) OIL: A Pump shipped from the factory does NOT have oil in the bearing housing.

Someone at the pump system site must set the proper amount of the proper oil prior to startup. It is a violation of several federal laws to ship oil in the pump, as oil is considered a hazardous substance.

2) IMPELLER clearance: Final impeller clearance must be set prior to startup. The factory sets the clearance at a nominal setting for the pump type and size, based on ambient temperature liquids, as the factory does not know the specific fluid temperatures or properties.

3) MECHANICAL SEAL: A pump shipped from the factory does NOT have the mechanical seal set, in hopes of preventing damage to the sealing faces.
The seal should be set only after adjusting impeller clearance, pump alignment, and rotational checks have been completed

4) ROTATIONAL DIRECTION: A pump shipped from the factory will NOT have the coupling spacer installed because you must first complete the driver rotational check. Additionally having the coupling removed helps in the process to set the impeller and seal. We have a 50% chance of guessing your local electrical phase rotation. If we are wrong, the pump becomes scrap metal.

5) ALIGNMENT: A pump shipped from the factory will NOT be precisely aligned to the driver.  The factory conducts/logs a rough alignment check during Assembly.

Even if we precision laser aligned the driver to the pump in accordance with NASA and USA Space Force standards, the very Nano-second the skid is picked up by a forklift or other device that alignment will disappear.

Note, that industry best practices (*1) dictate that a driver to pump alignment be checked/adjusted at least 5 times prior to startup. If you don’t know or are unsure about these 5 alignment stages, please check with your Regional Sales Manager.

(*1 Source TAMU Pump Symposium and Heinz Bloch “Pump Users Handbook”) 


A warning tag is attached to each pump to communicate these 5 key steps to the end user/installer. Of course these steps have always been stated in the IOM. The IOM is included with every pump, and can also be downloaded from our website in at least 5 languages.

Retort / Conclusion
Several people have retorted that the competition does these 5 things and so their pumps are “plug and play”. I have checked with several knowledgeable and key sources at these competitive firms and that URBAN MYTH is simply NOT true.

As a matter of fact, the other OEMs state they have the same errors / issues with their end users not heeding the warnings on installation and startup.

Exceptions: I will venture to state that perhaps some distributors may offer these 5 key steps as part of their value package. If you do then you are best in class and get a gold star.

More than a minute… Extra Credit
Post Script: On a recurring basis we have people rotate ANSI pumps backwards, consequently that trips the motor on overload. Why? Because the impeller will unscrew and “mate” with the casing. The operator subsequently corrects the directional issue (phase rotation), but does not disassemble the pump to check and correct the resultant damage.

Please note that if the impeller has “mated” with the casing there is a very high probability (99%) that the impeller will require replacement, repair and or rebalance, the casing will also require repair, and the shaft is now bent beyond specification, further the bearings and mechanical seal have been mechanically shocked.

Rotation in the wrong direction is a costly mistake.

From all of at Summit Pump…
we hope for all to have a prosperous 2019!

              Happy New Year // Feliz año nuevo // bonne année // Shana Tova //
????  (X?nnián kuàilè ) // ? ????? ????? (s novym godom)


– The Summit Pump Team

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You have choices
In the horizontal pump world of ANSI, the (14) mid frame pump sizes offer you a choice of selecting an MTO (medium) or an LTO (large) frame size. See sidebar below for more info.

Most often your competitor will choose the MTO over the LTO version because it is less expensive. They often choose the least expensive version because they don’t know or aren’t sure how to sell reliability, durability and the lower total cost of ownership (TOC).

I will acquiesce that some people will never be convinced regarding the “upsell”. At times I agree, depending on the pump duty and the duty cycle, that sometimes going cheap is indeed acceptable.

What is the difference?
The main difference between an MTO and LTO pumps ARE the shaft diameters. The MTO uses a 1-3/4” mechanical seal, whereas the LTO uses a 2-1/8” mechanical seal. Of course, this also affects the bearing sizes, both inboard (radial) and outboard (thrust), coupling hub size, and consequently the stuffing box size.

The larger shaft diameter directly correlates to a lower Shaft Deflection Index (L3/D4) rating as well. The lower the number, the less likely the shaft will deflect. See below chart:

All these “bigger sizes” do add up to more cost and a higher price, but they can also translate directly to higher reliability; meaning longer intervals between maintenance and lower total cost overall.

When and How do you decide to offer the LTO?
Before you decide, first consider some of the conditions the pump will experience. Look at the application, the fluid, the curve, the design point(s) and the duty cycle. Discuss with your customer where and for how long they will operate on the curve. Also ask if the customer had previous issues due to operations away from BEP?

Does the pump operate 24/7 or 5 minutes a month?
What is the energy level involved? (More important on a 50 HP application than 5 HP.)
Is the duty critical? Is there a backup pump in place?


We always recommend LTO over MTO when the following conditions exist:

  • Engine driven (intermittent torque application from combustion engine)
  • Belt drive (high cyclic stresses)
  • Operations away from BEP and approaching minimum flows or end of curve.
  • Conditions (fluids) that push the pump into a sleeved shaft configuration (higher L3/D4).
  • Applications with fluids that are viscous, non-Newtonion or high Specific Gravity (approach shaft BHP limits)
  • Fluid conditions /properties that push for a more sophisticated mechanical seal application (bigger seal).
  • Extreme temperature applications; over 325 F or under minus 20 F.
  • Variable speed applications; especially if it will run at low speeds at or below 900 RPM or has abrupt changes in speed. (Torque varies inversely with speed)
  • Applications with very low suction pressures or abrupt fluctuating changes in suction pressure. (Axial thrust increases as suction pressure decreases on end suction pumps.)

– The Summit Pump Team

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NPSHR and Impeller Diameter

Okay, this may take longer than 60 seconds.

Prior to computerized software for pump selection, manufacturers simply drew one NPSHR curve for the pump on the head versus capacity curve. It was used regardless of the impeller diameter chosen. This is not a good idea for the smaller diameter selections.

NPSHR for a fixed flow rate is less for the larger diameter impeller than the smaller diameter impeller. Or stated in another way, at a given flow rate the NPSHR increases as the diameter of the impeller decreases. (Note the head changes but the flow rate remains at some fixed value.)

As an alternative method to thinking about the science behind this, open your Summit Select program and select a Summit Pump model as below:

  • 2196 in 60 hertz
  • Perform a Design Point Search for ambient temperature water
  • 250 GPM at 65 feet TDH
  • Select the pump size 2 x 3 – 6 at 3500 RPM
  • Open the curve

You will note that for 250 GPM the 6.00 inch impeller will require about 11 feet NPSHR, the 4.63 inch impeller will require 13.3 feet NPSHR and the minimum 4.00 inch impeller will be 18 feet NPSHR.

The 3 condition points for the 2 x 3 – 6 (3500 RPM).

  • 250 GPM at 150 feet 6.00 inch and NPSHR 11.2 feet.
  • 250 GPM at 65 feet 4.625 inch and NPSHR 13.4 feet.
  • 250 GPM at 30 feet 4.00 inch and NPSHR 18 feet

Note your results may vary by a small fraction. Also be aware if you adjust the impeller trim from the original pump search, the flow and head will change due to the Summit Select’s predicted system curve at that trim.

– The Summit Pump Team

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API versus ANSI Pumps

API pumps are utilized in applications where pressures and/or temperatures are higher than ANSI standards allow. API pumps may handle fluids that are flammable, toxic, hazardous, and my favorite…explosive. API pumps should be used when safety is especially important. An example would be the release of toxic liquids or vapors to the atmosphere, which would compromise safety and/or some environmental restrictions.  API pumps can easily operate at temperatures over 1000oF, but are limited to 750 PSIG if the temperature is approaching 500oF.


There was a relaxation of API 610 9th edition about ten years ago. Consequently, some customers are rightfully trying to save money on applications where API compliance was really not justified. Other people are carelessly obsessed with trying to use an ANSI pump, as an API pump. We witness more and more inexperienced engineers attempting this substitution. As grandma used to say… “You should not try to teach a pig to sing…it just upsets the pig, and is a waste of time.”

Plenty of ANSI pumps are used in hazardous and high temperature applications, so when and how do you know which to use?

Consider an API pump if:

  • Liquid is flammable, toxic, hazardous or explosive
  • Head (TDH) is over 375 Ft.
  • Temperatures are over 350 degrees F
  • Driver horsepower is over 125 BHP
  • Suction pressure is over 75 PSIG
  • Driver speed is over 3600 RPM
  • Impeller diameter is over 13 inches

The following expression used by one company has worked well:   kW x RPM
If the result is greater than 675,000, they will likely use an API pump.

An ANSI B73.1 pump, by specification, is not as restrictive or detailed as an API pump, but it is also significantly less expensive, with shorter lead times.

Please work with your customers to know which one is required. Do not use an ANSI pump when it is obvious you should be using an API pump. Also, do not be afraid to use an ANSI pump on a tough application that is not specifying API pumps.


– The Summit Pump Team

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NPSHR versus NPSHA margins

From several sources I have recently studied: The minimum accepted margin between NPSHR and NPSHA should be a factor of 1.35 times the NPSHRor a minimum of 5 (five) feet (1.524 meters), whichever is greater. To eliminate the risk of cavitation to an acceptable level, the margin really needs to be a factor from 2 to 5 depending on the pump design and the fluid properties.

Remember, when the pump manufacturer publishes that the NPSHR is some value “X”, that really means the corresponding head for that pump has already dropped 3% at that flowrate.

Simply stated, the pump is already cavitating for the published NPSHR at that point. Want the specific background and data? Please refer to spec ANSI/HI 9.6.1 – 2017.

NPSH and Specific Gravity

Should you correct for the Specific Gravity when calculating NPSHA?

Technically, the answer is yes, but when calculating Net Positive Suction Head Available (NPSHA) for a given installation, Specific Gravity may or may not be ignored. If the suction source is below the centerline of the pump (“Lift” situation) and the source is open to atmospheric pressure, then you should correct for the Specific Gravity, but only if the value is greater than one (1.0).

If the source is above the centerline (“Flooded” situation) and the liquid’s Specific Gravity is less than one (1.0) then it can usually be ignored.

– The Summit Pump Team

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products in a timely manner,
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