As we mentioned in our other blog post, the pool pump is the heart of your pool. It just sits there quietly (or if you have an older model, noisily) circulating the water of your pool to help it stay clear and refreshing.

But has anyone ever wondered how it works? How the water gets moved around and why it is necessary? Today we’re going to explain the basics and demystify the heart of your pool so that whenever you hear that humming (or roaring) noise from your pool pump, you can rest assured that your pool water is getting circulated.

How water is Moved Around

Most people think that the pool pump “sucks” water through one end and gets released out the other. But the reality is it’s the other way around. The impeller, which is the only moving part of the pool pump (aside from the motor of course) actually creates a vortex and expels water through the outlet port, creating lower pressure or a vacuum at the intake which then creates that “sucking” of the water towards the pipe.

Most impellers today are “closed vane” impellers which have covers in the front part to draw the water in and out of the pump much more efficiently than the older open vane / vortex impellers. This new impeller design allows pumps with lower horsepower to move much more water than their older counterparts.

Why is it Necessary?

Your pool water needs to be circulated. The last thing anyone wants is a large pool of stagnant water where mosquitos, algae, debris and other unmentionables thrive in. Aside from the circulation, all of the water in your pool needs to be filtered out on a daily basis and your pool pump is the one in charge of moving all that water.

The Water Flow explained

Initial Filtering

The water is first drawn in through the intake pipes and the skimmers in the pool to your pump. This water is first filtered through the strainer basket that sits at the intake of the pump. The strainer basket is basically a plastic basket that catches large pieces of debris that might clog up your impeller or even chip it. Remember, the impeller is spinning at a very fast rate, even if it is made out of very sturdy stuff, a small pebble or piece of hard debris can chip and crack it. This is the reason why it’s always prudent to clean out your strainer basket every so often and check if there’s damage to it and replace it if there are visible cracks where bigger pieces of debris can get through. It’s much cheaper (and easier!) to replace a strainer basket than it is an impeller.

Second Filtering

Once the water has gone through the initial filtering through the strainer basket, it is then forced by the impeller through your main filter. This can be your regular canister filters or your sand filter. This second filtering stage takes care of all of the smaller particles that the strainer basket didn’t catch. These include algae spores, dirt, tiny bugs, and all of the other stuff you don’t want floating around in your pool. After being pushed through the filter, the water is then pushed through the heater (if you have one) and then through the chlorinator before exiting the pool as fresh and clean water.

Curious about how a pool heat pump works? Click here for a detailed dive into the topic.

Warning Signs to Look Out For

Sometimes something doesn’t feel right with your pool water this can be a sign of a damaged or clogged impeller. Here are some telltale signs that your impeller needs checking up on:

  • Through the clear lid of the pump, the strainer basket doesn’t fill up with water (keep the lid closed and sealed)
  • The water flow is slower than normal
  • The pump is making loud, low grinding noises, or what’s known in pool-speak as cavitation noises.

If you observe any of the symptoms mentioned above, try and giving your impeller a quick check, it hopefully may only be clogged with debris that the strainer basket missed. If it is damaged, replace it immediately as keeping a cracked impeller might lead to it shattering and can lead to catastrophic pump failure.

Seals are Important

Everyone loves seals, they’re cute and cuddly. Wait, not those types of seals. Most of the time, pool pump problems are caused by damaged and worn out seals or O-rings. Your pool pump is a closed system with every section sealed off by O-rings so that water needs to go where they’re going and air needs to stay where they’re needed. There are four seals that you need to check if your pump is still showing signs of problems once you’ve ruled out a clogged or damaged impeller.

  • The Lid Seal or O-ring (Located in the strainer lid)
  • The Diffuser Seal or O-ring (Located just above the cone tip of the diffuser)
  • The Housing Seal or O-ring (Located at the seam of the housing and the motor seal plate, also known as the seal plate O-ring)
  • The Shaft Seal or O-ring (Located under the impeller on the shaft of the motor)


Check that all of your O-rings smooth and show no signs of being brittle, clean out any debris that might be on the O-rings. If you find any seals that are worn out or damaged, replace them immediately.  

Pool pumps do more than just move water around. Draws all of the stagnant water from your pool and feeds them into the systems that keep your pool water crystal clear and clean. While pool pumps are built like tanks and can last for years on end, they will require a bit of maintenance every now and then. We've experienced this before and made sure to stock every part that's needed to maintain your pool pump on our online store.

Do you have any questions about this topic or the featured products? No worries, we're here to help! Drop us a question down below and we'll get back to you ASAP.

Happy swimming :)

We Need This
We Need This
We Need This
Thank you!

Leave a comment

All comments are moderated before being published