Keeping your pool clean and inviting doesn’t have to be a chore, but there are a few essential steps to get right. One of those is backwashing your filter.
If you’re not quite sure what backwashing involves, how often to do it, or why it matters, don’t worry. You’re not alone. Many pool owners, especially first-timers, aren’t familiar with the process. This guide will walk you through everything you need to know about how to backwash a pool, step by step.
Whether you're happy doing your own maintenance or just want to understand the basics before booking a service, this is a great place to start.
What is Backwashing?
Backwashing is a cleaning process that removes the dirt and debris trapped inside your pool’s filter. Over time, your filter collects all kinds of contaminants: dust, oils, leaves, and other fine particles. Eventually, it starts to clog up, which affects how well it can clean your water.
To fix that, you run water backwards through the filter, pushing the built-up debris out through a waste outlet. It’s like giving your filter a good rinse so it can keep doing its job properly.
Does Your Pool Filter Need Backwashing?
That depends on what type of filter you have. There are three main types used in residential pools across Western Australia:
Sand Filters
Sand filters are popular for good reason; they’re reliable and relatively easy to maintain. Water flows through a bed of sand that traps particles. You need to backwash these filters regularly to flush out the collected debris.
Diatomaceous Earth (D.E.) Filters
These filters offer the finest level of filtration. They use a powder coating (called diatomaceous earth) on grids inside the filter. Like sand filters, you clean D.E. filters by backwashing them, but you’ll also need to add a fresh layer of D.E. powder after each clean.
Cartridge Filters
These use a large, pleated cartridge to trap debris. Unlike sand or D.E. filters, you do not backwash a cartridge filter. Instead, you manually take out the cartridge and hose it clean.
When Should You Backwash a Pool?
Knowing when to backwash is key. If you do it too often, you’ll waste water and can disturb the filter media. If you leave it too long, the filter becomes less effective and puts strain on your pool equipment.
Here are the main signs it’s time to backwash:
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Your filter’s pressure gauge is reading high
This is the most reliable indicator. When the pressure climbs about 50 kPa above your system’s normal ‘clean’ level, it’s time to act. -
The water flow seems weaker than usual
If the return jets are less powerful, your filter might be clogged. -
Your pool water looks cloudy or dull
If your chemical levels are balanced but the water still looks off, it could be due to a dirty filter.
As a rough guide, most pool owners backwash their filters about once a month during the swimming season, but always check your pressure gauge first.
How to Backwash a Pool Filter
If your pool uses a sand or D.E. filter, backwashing is something you’ll need to do regularly to keep the system running smoothly. The process is fairly simple and takes just a few minutes, but it’s important to follow the steps in the right order to avoid damaging any equipment.
Here’s how to backwash a pool filter the right way:
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Switch off your pump and chlorinator
Always start by turning everything off. Adjusting your multiport valve while the pump is running can damage the internal gasket or cause leaks. -
Connect your backwash hose
Attach it firmly to the waste port on your multiport valve. Position the other end in a safe drainage area, such as a stormwater outlet. Avoid draining chlorinated water onto lawns or garden beds. -
Set the valve to ‘BACKWASH’
Push down on the valve handle and rotate it until it clicks into the backwash position. -
Turn the pump on and run it for about two minutes
You’ll see dirty water flowing through the sight glass. Keep it running until the water becomes clear. -
Turn the pump off again
Always power down before changing the valve setting. -
Set the valve to ‘RINSE’
This step helps settle the filter media and flush out any remaining debris. -
Run the pump for another 30 seconds
You should see cleaner water moving through the sight glass during this cycle. -
Turn off the pump and return the valve to ‘FILTER’
This is the normal setting for day-to-day filtration. -
Turn the pump back on and bleed any trapped air
Open the air release valve on your filter (if it has one) until a steady stream of water flows out, then close it. -
Check your water level
Backwashing lowers the pool water. If your water level drops below halfway up the skimmer box, top it up before you continue normal operation.
This quick routine restores your filter’s efficiency, helping to maintain good water flow and clarity without the need for harsh scrubbing or manual cleaning.
What the Valve Settings Mean
Your multiport valve can be confusing at first. Here’s what each setting does:
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FILTER: Normal setting for day-to-day use
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BACKWASH: Reverses water flow to clean the filter
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RINSE: Settles the media after backwashing
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WASTE: Sends water straight out without filtering (useful for lowering the water level)
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RECIRCULATE: Circulates water without passing through the filter
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CLOSED: Blocks all water flow (never run the pump in this position)
Why Regular Backwashing Matters
It’s easy to put off backwashing, especially when the water still looks okay. But a dirty filter can cause bigger problems down the track.
Here’s why it’s important:
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Cleaner water, faster
A clean filter removes fine particles more effectively, helping your pool look sparkling, not just ‘mostly clear.’ -
Less strain on your equipment
A clogged filter makes your pump work harder, which can shorten its lifespan. -
Better chemical efficiency
When water flows freely, your sanitiser circulates properly. That means fewer algae problems and less chemical wastage.
Take the Hassle Out of Pool Maintenance
Learning how to backwash a pool is a key skill for any pool owner. By keeping an eye on your pressure gauge and following these simple steps, you can ensure your filtration system runs efficiently, keeping your water beautifully clear all year round.
But we know that life gets busy. If you'd rather spend your weekends enjoying your pool than maintaining it, professional help is always available. A team of licensed technicians can handle everything from regular maintenance and backwashing to equipment repairs and upgrades.
At Pool Assist, our passion lies in making pool ownership easy. For expert advice or to book a professional pool service, get in touch today or visit us in-store in Myaree. Let us help you enjoy a healthier, hassle-free pool experience!
Note: This post was originally published on May10 , 2021 and has been updated on October 30, 2025.