Parts of a Pool Pump

Identifying Major Pump Parts and Their Functions

A person who has had the pleasure of seeing the innards of a pump (opened by their own hand or glancing over the shoulder of a technician) may have noticed it looks simpler than expected. After all, the pump is this piece of machinery that can pump 80 gallons or more a minute, leaving one to expect a few bells and whistles hidden away inside the casing. But in practice, the pool pump can be broken down into two categories of parts; the drivetrain and the outer structure. Or put simpler, the parts that push and pull the water and the ones that keep it from leaking.

Today’s blog is centered on identifying pool pump parts, so Average Joes can either fix it themselves or at least use the right terms when talking to a tech. A side note, before I learned how to drive, my grandfather demanded I know what the basic parts of the car were and their function before I could get behind the wheel. That mindset was to impart two points: 1) Understand how my machine works so I can utilize it, 2) If I pay someone to fix it, know if they are trying to cheat me on parts. The latter is the most important to me as someone who appreciates an honest repairman. And not the least of which is an honest pool equipment technician.

My grandfather passed on the lesson of knowing the mechanics before the drive, so I want to pass on that same lesson to you. So let’s break down the parts of a pump and see how they contribute to the overall functionality.

The Housing

Parts of a Pool Pump
Inside a Pool Pump Housing

If the pump is thought of like a ship, the housing would be its hull. All of the pump’s inner workings – the impeller, diffuser, seals, and motor – fit in or onto this outer casing. The standard housing material is currently the high impact plastic composite called Noryl. This resilient, lightweight material is rustproof and holds up extremely well under duress from heat, rain and water pressure.

Older pumps (early ’80s and back) were made of brass or bronze; these materials proved to be extremely durable, but costly to maintain. A plastic injection molded impeller is going to be a bunch cheaper than a brass version that has to be smelted and forged. Also, your back should thank pump manufacturers for switching to plastic because those metal pumps weigh upwards of 100 pounds. Metal pumps were really durable workhorses and can still be found on pools today.


The strainer lid is the pump’s main inspection point from which a technician or homeowner can determine a system’s health. If we find large air bubbles or no water at all in the strainer lid while the pump is running, that could be a sign of an air leak along the suction side.  Because of its necessity as an inspection point, the lid is made of a clear or tinted Lexan glass.  If you are unfamiliar with Lexan, it is the material used in bulletproof windows and other glass-like materials.

Strainer Basket

The strainer basket collects debris before it reaches the important parts of the drivetrain. This basket can save you a bundle just by preventing hard debris like pebbles from surging into the pump and chipping the impeller.

Gaskets & Seals

Pool Pump Gaskets

The gaskets and seals are what keep your equipment pad dry and your water moving. A bad set of gaskets can have your equipment area flood or a pump filled with air rather than water.  There are four main gaskets and seals on a pool pump:

  • Lid Gasket – located on or under the strainer lid.
  • Diffuser Gasket –  Found on the cone tip of the diffuser.
  • Housing Gasket – Largest of the gaskets and found in the seam between the main housing on the motor seal plate. This gasket is also called the seal plate gasket.
  • Shaft Seal – The two-sided seal that sits underneath the impeller on the shaft of the motor. This is the most important seal as it prevents water from surging into the motor and causing fatal damage.

Seal Plate

The seal plate is a motor’s mounting flange that allows it to be secured to the pump housing. The seal plate is named so because it houses the shaft seal that encloses around the shaft to prevent water leaks into the motor. This is made of the same Noryl plastic as the housing, making it lightweight and super strong.

The Drive Train

MotorCentury UST1102-5 (1)

The driving force behind the pump is its motor which creates the churning force necessary to prime the pump and circulates water. The standard is single speed induction motors, but they are slowly losing ground to dual speed and variable speed motors. Variable speed and dual speed have grown into popularity due to their energy efficiency and have also been bolstered by electric companies offering rebates for homeowners who choose to upgrade.

Most single speed motors run a dual voltage setup which allows them to run on either 230 or 115 voltage (user must adjust voltage before installing). Variable speed and most dual speed run strictly on 230 voltage; there are some exceptions in the dual speed category that run on 115.

ImpellerHayward SP2610C-4

The impeller is what makes all the magic happen; magic meaning, transforming the spinning shaft of the motor into the pulling force for pumping. An impeller is essentially two discs glued together to sandwiching fan blades (also called veins). The front disc has an opening with a porthole to focus the churning power of the impeller towards the suction pipe to the pool. The water is pulled through the impeller’s face and then expelled through the impeller’s slotted sides – it’s H2O’s version of a merry-go-round. The water is then rushed back to the pool.


We call this an impeller accessory and a very important one at that. A diffuser amplifies the pull of the impeller by creating a tightly enclosed vacuum lock to the front housing to maximize its power. The diffuser resembles a funnel or a cone that shrouds the impeller; its tip butts up to the front housing, sealed by the diffuser gasket. As the impeller spins, the diffuser shroud concentrates the turbulent energy of the impeller towards the suction pipe which makes the pump prime.

Impeller Ring
The Impeller Ring…My Precious

Impeller Ring

The impeller ring, aka the wear ring, is a plastic ring that fits to the tip of the impeller. The purpose of a wear ring is to act as an extension of the impeller tip to ensure a seal between the impeller and diffuser. The centrifugal force of the impeller forces the wear ring to affix to the diffuser to ensure an even tighter vacuum for priming and pumping.  Wear rings are not found on every pump style but are usually seen on high pressure and high head style pumps, i.e. Hayward Super II or Pentair Challenger.

Impeller Screw

Hopefully, you have read my previous blog concerning the importance, or better yet unimportance, of the impeller screw. The impeller screw is meant to secure an impeller to internally threaded shaft motors. The impeller screw is quickly becoming obsolete as most manufacturers switched to external thread motor shafts. This change to external threads allows for the impeller to be screwed directly to the motor shaft without the need for extra securing. The thread type of the new impellers also means the impeller is being spun in the direction that keeps it tight to the motor to prevent any slippage.

Thank you for your time and hopefully you learned something about your pump. If you’re still in need of more information, please do not hesitate in calling our techs at 877-372-6038. We’re glad to help.

click here to find your replacement pool pump parts

17 thoughts on “Identifying Major Pump Parts and Their Functions

  1. When I opened by pool water pump, between the motor and the “bracket”, we can see the shaft going into the bracket (where the impeller is located). On that part of the shaft near the motor I can see a so called slinger. What is its function? There should not be any water in the area. And how does it stay close to the motor and not move along the shaft?

    1. I’ve never gotten a clear explanation of the function of the water slinger. But my best guess is that it is the last barrier preventing water from traveling down the motor shaft to the motor bearings, kind of like a hilt cover.

  2. Where does the diatomaceous earth go in the system? Is it found in the pump, or outside of it somewhere? How is it housed?
    Thank you very much!

  3. I just recently replaced the shaft seal on my Hayward TriStar pump. When putting back together and comparing to a parts diagram, I discovered there was no Impeller Ring. The pump was installed many years ago and since that time we had the diving board removed and a waterfall installed in its place. Also, at some point a repairman replaced the motor and upgraded from 1 hp to 2 hp. Not sure if this was done at the same time or on a different repair, but I’m wondering if the Impeller Ring was accidentally left out or was this intentional because of the motor change and/or pressure change caused by the addition of the waterfall. So I’m wondering if I need to purchase a new Ring and install. Thanks for any reply and thanks for this forum.

    1. The Hayward TriStar uses an impeller ring; there’s no reason that I think of to have not used it. If the pump is working, you can leave it as is, but if you want it to work at its highest efficiency, get a new wear ring.

        1. Please re-explain the question. I read your comment, but there is no question mark in the entire paragraph, so I took the best guess of what you were asking.

          From what I read, you asked if the impeller ring is necessary. I stated the impeller ring is necessary for the pump to work at its highest efficiency. You are also wondering if the impeller ring was left out intentionally or by accident; this would be an inquiry for the person who repaired it at the time. I don’t know what they were thinking at the time of the repair. But as I said above, for the impeller to draw the amount of water it is designed for, the impeller ring is necessary. If the impeller size was not upped along with the motor, the flow rate hasn’t changed. You could put a 15HP motor on a 1 HP impeller, and the pump will only draw 1HP worth of water.

          If the flow rate hasn’t changed there’s no point in not installing an impeller ring. And also, I fail to see the reason why someone would “upgrade” a pump horsepower just to handicap its top-end flowrate by not installing the impeller wear ring.

    1. Going by this definition of a hydrosphere, I don’t think a part like that could fit in a pump: “all the waters on the earth’s surface, such as lakes and seas, and sometimes including water over the earth’s surface, such as clouds.”

  4. I needed information about an impeller ring and what it does – this was helpful. I see you around pool blogs a lot. I like you. Funny comment about the “precious”

Leave a Reply

Your email address will not be published.

Recommended Resources

What does HP SPL mean on a Pool Pump Motor Label?

What does HP SPL mean on a Pool Pump Motor Label?

Horsepower Specials (HP – SPL) or “overrating” spa pumps is a decades-old tradition of manufacturers inflating a motor’s HP to make...
Read Now
How much does a swimming pool cost

How Much Does a Pool Cost? 93 Real World Examples

How much does a pool cost is a question I get asked all the time. When I started writing this article...
Read Now

Sizing Your Above Ground Pool Pump

Sizing your above ground pool pump is crucial to the overall performance of your swimming pool. An undersized pump lacks the...
Read Now
Poolside Chat Episode 11: How Many GPM Does a Pump Motor Push?

Video: Poolside Chat Episode #11 – What is My Motor’s GPM Rating?

This is Poolside Chat where every week we answer your questions on how to fix and maintain your swimming pool. Poolside...
Read Now

Looking for pool parts?

Shop Motors Shop Filters Shop Pumps Shop Salt Systems Shop Lights Shop Cleaners
Copyright © 2024 INYOpools All rights reserved