How A Pool Pump Works

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This page provides a short tutorial on the main parts of a pool pump and how a pool pump works. This example describes a Hayward Super II Pump but the pool pump's parts and it's operation are common to most pool pumps.

Things You'll Need

Video

Step by Step

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Step 1

This picture shows the main parts of the pool pump in a pump cut-away. These parts include: the strainer basket cover that provides access to the strainer box to add water and clean out debris; the strainer basket that filters the larger pieces of the debris; the diffuser that direct water to and collects water from the impeller; the impeller that generates water pressure through centrifuge; and the motor that drives the impeller. Also shown are the two ports where water enters into the pool pump from the pool and exits out or the pump to return to the pool.

Step 2

This picture shows the basic flow of water through the pool pump. Water is sucked in through the basket, through the center of the diffuser (yellow) and through the center of the impeller. As the impeller spins, the water is thrown out the outer slots of the impeller where it is collected by the diffuser. The water is then funneled though slots in the diffuser into the high pressure water chamber and then out the exit port to the pool. Two notes: this picture shows a cut-away of the pool pump so that you can see the internal parts of the pump. In a working pump the diffuser would completely enclose the impeller. Also the only moving part in this pool pump is the impeller driven by the motor shaft. It's centrifugal motion is what sucks the water in and pushes the water out under pressure.

Step 3

This picture shows the inner operation of the diffuser with the diffuser partially pulled off. The diffuser funnels water from the strainer pot into the center of the impeller, then collects spun water from the outside edges of the impeller and releases the water through its own slots into the pressured chamber (dark blue arrows).

Click here to view the Hayward Super 2 pump parts. 

Step 4

This picture shows the operation of the impeller. Water enters the center of the impeller. As the impeller is spun by the motor, a series of blades, like a fan, push the water to the outside edges of the impeller where it exits through slots to be collected by the diffuser. It is this centrifugal force that generates the high pressure of the water exiting the pool pump.

Step 5

The pool pump has two chambers: chamber 1, the strainer pot, in the pull side of the pool pump before the impeller; chamber 2 is the push side of the pump after the impeller. There are four seals that keep the water flowing correctly between the chambers.

Step 6

This cut away of the pool pump shows the 4 seals that are part of most pool pumps: the strainer pot gasket, the diffuser gasket, the housing gasket, and the motor shaft seal. Their deterioration is the source of many of the common pool pump problems that plague pool owners.

Step 7

The strainer gasket usually sets in a groove on top of the strainer pot and provides a seal for the strainer pot cover. A poor strainer gasket will allow air to be sucked into the pump and prevent priming. The instructions for replacing a pump lid O-ring are included in the following guide: How To Clean Out the Pump Strainer.

Step 8

The diffuser gasket provides a seal between the strainer pot and the chamber around the diffuser and impeller. This chamber collects the pressurized water that is released through the output port. Without this seal the pressurized water will blow back into the strainer pot and the pool pump will loose pressure. For instructions in how to replace a diffuser gasket go to How To Replace Pool Pump Gaskets.

Step 9

The housing gasket provides the seal between the motor assembly and the pool pump assembly. If this seal is bad, the water will spray out of the pool pump and you will loose pressure and water. For instructions in how to replace a housing gasket go to How To Replace Pool Pump Gaskets.

Step 10

The motor shaft seal prevents water from leaking out of the pressure chamber along the motor shaft into the motor assembly. When this happens you will see water dripping from the bottom of the motor. For instructions in how to replace a motor shaft seal go to How To Replace A Motor Shaft Seal.

Step 11

If you are repairing your pump or pump motor consider purchasing a GO-KIT. Each GO-KIT contains the replacement seals and gaskets you will need to repair your pump. A typical GO-KIT like the one pictured here for a Hayward pump, contains the motor shaft seal (2 parts), the pump housing gasket, the pool pump lid o-ring and the diffuser gasket. Note: These GO-KIT are generally unique to the make and model of the pump. Order the GO-KIT specified for your pump's make and model.

Click here to view GOKITS. 

Comments

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(81 to 120 of 121)

InyoPools Product Specialist  Posted: 6/4/2012 

JimmyRay1020 - It could be one of three problems. 1- check to see that your impeller isn't jammed with debris; 2- check your motors capacitor(s) - they give the motor a kick to get it moving, and then 3- check the motors bearing - does the shaft rotate freely. The first two are relatively minor. The last may require you to replace the motor.
 Reply

InyoPools Product Specialist  Posted: 6/3/2012 

Jim - You could have a loose impeller rubbing on the diffuser but it's more likely to be the motor bearings. 5 years isn't a bad run on motors these days. Check the impeller. If it's good and you can wait 3-5 days downtime for a motor replacement, wait until the motor goes and get another one. You can't predict when the motor will fail. Generally it's when you need it most.
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 Posted: 6/3/2012 

I recently opened up my pool this year, and when attempting to turn the pool on, the pump merely sits there and hums, and nothing, else, it's as if it is almost "stuck" or something. No water flow whatsoever, and there is no ability to engage the filter or no water being "pumped". Please do not tell me that the pump requires replacement. My neighbor stated that I may have to take the pump apart, lube the gaskets, check the bearings and see if you can ease the motor into rotation. I have no expertise on this. Could you give me some assistance please!!!
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 Posted: 6/2/2012 

I have a Hayward 1 1/2 hp superpump and it's 5 yrs old. It's running much louder as of late but seems to have good pressure and pumping like normal. Can the impeller simply be dirty inside or is it a bearing or something bad in the motor. How long do I have approx before it fails on me. I thought Hayward was top of the line stuff. I just can't see replacing the motor every few years. Help
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InyoPools Product Specialist  Posted: 6/1/2012 

rushpool - If you had a lot of debris in you pool, it may be clogging your filter. Try to clean as much of the debris out with your net. You may have to backwash or clean your filter several times until the debris is out of your pool.
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 Posted: 5/30/2012 

Hi, I have a 21' above ground and opened the pool this week. What would cause the dischrge flow (back into pool) to slow down (less force) after a few hours of pumping..suction is strong at the skimmer but lessens over time. No leaks aparent..Help please..Thanks...
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InyoPools Product Specialist  Posted: 5/24/2012 

Candy – It sounds like you have to replace the housing gasket and motor shaft seal. See our How To Guides on replacing gaskets/seals.
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 Posted: 5/22/2012 

I have a Hayward 1.5 70 gpm I turned it on and it was leaking water at the back of the motor and spraying out a little in between the basket and motor I had good pressure coming out of jet but I turned it off because I know that it should not be doing that
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InyoPools Product Specialist  Posted: 5/22/2012 

BP - If water still flows after you turn off the pump, you may have a partial blockage in you lines or pump. Check for debris inside the pump and in particular around the impeller. Make sure your filter and strainer basket are clean. As a last resort, have someone check for blockages in your lines.
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 Posted: 5/21/2012 

After turning on the pump (Pentair Whisperflo 1hp) for the first time this year, it ran for a few minutes and then stopped, but water was flowing. The pump was very hot. It cooled down and then the same problem repeated a few times. What would cause the pump to overheat and how do I figure out what to replace? Thanks for your help.
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InyoPools Product Specialist  Posted: 5/16/2012 

mssissy - You may get by with just replacing the capacitor. If you can't turn the impeller, it may be blocked with debris or the motor may be frozen and need to be replaced.
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 Posted: 5/14/2012 

I have a Hayward 2hp pump, roughly 2-3 year old. I opened my pool this weekend and the pump will not draw water in, it will turn on make an odd sound and kick off. I am not well educated in pool operation as I acquired the pool with the home. Does this sound like it needs replaced or tuned up. Please help

sissy in pa

 Reply

InyoPools Product Specialist  Posted: 4/30/2012 

Most pumps do not have an on/off switch. That function is usually controlled at the circuit breaker
 Reply

Anonymous  Posted: 4/29/2012 

Is there a on & off switch?
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InyoPools Product Specialist  Posted: 4/17/2012 

Mamma Jules - Unfortunately, we do not sell that part.
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 Posted: 4/16/2012 

The cover on the end of the moter we need to replace, what is it called and can I buy the replacement?
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InyoPools Product Specialist  Posted: 4/2/2012 

virtual777 - The pump impeller is a good place to start. Also check the seals around the pumps. Is any water leaking or spraying around the pump. If so your pump has lost prime and will not move water.
 Reply

 Posted: 4/1/2012 

I have a heyward 1hp, i replaced the pump 2 years ago. It was working fine last week and now it seems the pump is spinning and sounds fine but no water motion at all. I am not sure if the impeller has come loose or if it could be the impeller is clogged. Any thought before i start disassembly.
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InyoPools Product Specialist  Posted: 3/19/2012 

Becky - Check the power, breakers, switches, etc. If you have a timer on the system, make sure it is working properly.


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 Posted: 3/18/2012 

We bought a1hp water pump motor we installed it but now it doesnt work please help m
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InyoPools Product Specialist  Posted: 3/8/2012 

rik - These motors generally last between 3-5 years. The model C48K2N143B1 or UST1102 is $160 and is available. Be sure to replace the shaft seal when you replace the motor to your pump.
 Reply

 Posted: 3/7/2012 

I have a 1 HP Hayward Super Pump (AOSmith) (Model# C48K2N143B1) Can you tell me cost and availability???? Also, the pump works, but makes a loud vibrating buzz when running. I'm thinking of replacing it, but it's only 4 years old. What is the average lifespan of this pump? Thank you.
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InyoPools Product Specialist  Posted: 2/19/2012 

TAPU - Sounds like you may have had a partial blockage in your system somewhere and it cleared when the black residue came out. One common point of blockage is at your impeller. See our How To Guide on "Cleaning out a Pool Pump Impeller" to make sure your impeller is free of debris.
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 Posted: 2/17/2012 

My 2HP A.O. Smith Pump P# 1717789722 (can't find the pump under parts) is making humming noise when it want s to start and it takes a while for the pump to get the water flow starting. as soon as the water flows through the pump the humming noise stops and it seems to work. Now the pump got really hot and pushed black residue into the pool. I cleaned up the pool, pump seems to be working and no black residue. What happened?
 Reply

InyoPools Product Specialist  Posted: 1/17/2012 

Dick, Your 2 HP pump is designed to generate from 20 to 60 GPM at the low speed according to the performance chart. The actual GPM varies according to the resistance in your pool lines which is determined by a number of factors including pipe size, number of lines to and from the pool, length of pipes and number of fittings plus others. Someone had to have calculated this flow to size your pump and filter. If you can't get that number you might install a flow meter in one of your pipes to monitor flow. You need at least 40 GPM for your size heater. According to the manf, if you are over that number, you can heat your pool efficiently at the lower speed. The flow will be slower but the water will be hotter.
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 Posted: 1/16/2012 

Just for the record can you tell me what the gpm rate is at lo speed with my new Whisperflo 011523 2hp pump? I am not sure I am able to understand the chart on page nine of the owners manual. My new Rayvac heater manual says it needs 40 gpm to operate. I imagine a more important issue is: How efficient is it to try to heat the pool or spa at lo speed? By the way, I really like my new pump. it is quieter than the Hayward by a lot and in lo speed, you can not hear it run. you have to feel the motor to tell if it is running. Nice Job!!!
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InyoPools Product Specialist  Posted: 1/16/2012 

Dick in AZ - The rubber toggle switch on the back side of the motor is used to manually change the motor speed between low and high. Generally people do run this motor at high speed on start up to prime the system than back it off to low speed after 5-10 minutes. The only delay in changing speed is about 15 seconds to change the flow of water. Generally heaters will not operate at the low flow rates. They shut off at 20-40 GPM to keep the heater cores from overheating. Likewise the in floor heater must run at the higher speed to operate efficiently.
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 Posted: 1/15/2012 

My pool supply guys just installed a Wisperflo 011523 2hp dual speed pump as a replacement to a old Hayward. What is the Rubber covered toggle switch on the back side of the motor?

The owners manual (revision G) does not say much about using the low speed feature. Where can I get more info about using this with a Raypac heater and a Caretaker in floor cleaning system. The low speed seems to operate at about 4 lbs pressure sometimes and Zero lbs pressure at other time with no rime or reason. We have a Jandy in house remote controller. Is it true that the motor must start at high speed and then switch to low speed? Is there a delay of some sort between changing speeds? I would appreciate a detailed explanation as to what is happening when we change speeds. Can we run our heater with low speed? How about the in floor cleaning system?

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 Posted: 1/3/2012 

Dan - I would check the impeller to make sure the blades are all intact and the slots are not clogged with debris. Also check that the impeller does not wobble on its shaft. The threads sometimes wear with age. Check the diffuser for cracks and wear between the difusser and impeller. If you haven't replaced your filter cartridge or sand for a number of years, I would consider that also.
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 Posted: 1/2/2012 

I have a P4RA6G-152L Dura-Glas II 2 HP Pump. The flow has decreased over the years at the pool outlets. If I replaced the Impeller or Diffuser would the pump deliver more water volume?
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 Posted: 1/2/2012 

Great information!!!!!
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InyoPools Product Specialist  Posted: 11/26/2011 

David, You could probably get by with just replacing the motor but 11 years is fairly old for a pump. I would recommend replacing the whole pump. Look at the more energy efficient options.
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 Posted: 11/25/2011 

I have an old pump, over 11yrs and it quit working as i was closing my pool. I heard a rattling noise, so cleaned filter but wasn't too dirty. Then turned on pump and it made ahumming noise. Turned off and back on then got nothing. Should I replace the whole thing? or maybe just the motor?
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InyoPools Product Specialist  Posted: 10/5/2011 

Mark, Sounds like one of your pump gaskets or seals has gone bad and needs to be replaced. See our guides on How to Replace a Motor Shaft Seal or How to Replace Pool Pump Gaskets.
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 Posted: 10/4/2011 

MY POOL PUMP MOTOR LEAKS WATER ALL THE TIME!!!
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InyoPools Product Specialist  Posted: 9/29/2011 

From your description it sounds like your motor bearings are going and should be replaced soon. Many motors start to fail after 7 years. Your pump housing is still probably good so all you have to replace is the pump motor - cheaper. See our guide on "How to Replace the Motor on Your Pool Pump" to get an idea of what's involved.
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Anonymous  Posted: 9/28/2011 

My filter is a Hayward & I thought the pump was also a Hayward however the pump indicates the name "Magnetik Centurian". I was thinking I needed to replace it as it is making a very loud noise as it does it's work. Sounds like bad bearings or some kind of rubbing) Interestingly the pump is working fine (as far as pumping rate. Should I replace it or have it checked out for repair. I'm just leary about repair as I don't want to get stuck with a relatively cheaper repair (as compared to replacement)only to have it go haywire again. The pump is 1.5 HP & is about 7 years old.

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InyoPools Product Specialist  Posted: 8/31/2011 

Sounds like you might be having a problem with your start capacitor. Look at our How To Guide on Replacing a Pool Pump Capacitor under "Pumps". If not you may have more serious problems in the windings of your motor.
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 Posted: 8/31/2011 

Plz help my pump stopped working. It humms for like 3 seconds than quits. Cleaned all the lines. Plz help me. New pool owner. The pump is two months old.
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Anonymous  Posted: 6/21/2011 

I was just curious if a Jandy pool pump and impeller works the same as hayward?
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