Keeping your pool water clean and your filtration system running efficiently is key to getting the most out of your swimming pool, used seasonally or year-round. One of the most essential maintenance tasks in this process is backwashing.
While it may sound technical, backwashing is straightforward once you understand the steps. This guide will explain what it is when performed, how to do it properly, and how it fits into your overall pool care routine.
What Is Backwashing, And Why Is It Important?
Backwashing is a cleaning process that clears out your pool’s filter by reversing the water flow. Usually, water passes through your filter media (such as sand, glass, or DE powder), which traps debris, dirt, oils, and other particles.
Over time, the filter becomes clogged with these contaminants and its efficiency drops. That’s when backwashing comes in.
By sending water through the filter in the opposite direction, debris is flushed out and expelled through the waste line, leaving your filter refreshed and ready to keep your water crystal clear.
Backwashing improves circulation, helps maintain water clarity, and extends the life of your filtration system.
When Should You Backwash Your Pool?
The pressure gauge on your filter system is the best indicator that it’s time to backwash your pool. When the pressure rises 8 to 10 psi above the normal operating level, it’s a sign that the filter is becoming clogged and needs to be cleaned.
How often you need to backwash depends on several factors, including the type of filter you have, how often your pool is used, and how much debris it collects. For example, pools surrounded by trees or used frequently require more regular backwashing.
In general, sand and glass filters may need backwashing every one to two weeks during peak season, while DE filters are usually backwashed once a month.
You should also consider backwashing after heavy storms, high bather loads, or if the water appears cloudy despite balanced chemistry.
How To Backwash A Pool With A Sand Or Glass Filter
Sand and glass media filters are among the most common types found in UK residential pools. The backwashing process is pretty straightforward, but it must be done carefully to avoid damaging your system.
To begin, ultimately, always turn off your pool pump. Adjusting the multiport valve while the pump is running can damage internal components. Once the pump is off, turn the multiport valve to the “Backwash” setting.
Turn the pump back on and let it run for two to three minutes or until the water in the sight glass runs clear. You’ll usually see dirty, cloudy water first, followed by clear water as debris is flushed out.
Once backwashing is complete, turn off the pump again and switch the valve to the “Rinse” position. This step is crucial; it settles the filter media and prevents dirty water from re-entering the pool.
Run the rinse cycle for about one minute, then turn the pump off, set the valve back to “Filter,” and restart the pump.
Your filter is now clean and ready to go.
How to Backwash a Pool With A DE Filter?
Diatomaceous Earth (DE) filters operate slightly differently and require more attention. Instead of sand or glass, these filters use a fine powder from fossilised algae to coat internal grids and trap even the tiniest particles.
To backwash a DE filter, follow the same initial steps: turn off the pump, set the multiport valve to “Backwash,” and run the pump until the water runs clear—usually about one to two minutes. After that, perform a short rinse cycle, then backwash again for 30 seconds, followed by a second rinse.
Repeat this sequence with a 15-second backwash to ensure a thorough clean.
Once finished, reset the valve to “Filter” and turn the pump back on. The final step is to recharge the filter by adding fresh DE powder, usually through the skimmer. This ensures the grids are adequately coated and the filter performs at its best.
Where Should Backwash Water Go? (UK Considerations)
In the UK, there are environmental regulations regarding the disposal of pool water, including water used during backwashing.
Because this water often contains chemicals and contaminants, it should not be discharged directly into storm drains, natural water sources, or the public sewer system without authorisation.
The ideal solution is to connect your waste line to a dedicated soakaway or drainage pit in your garden, well away from the pool and surrounding structures. If your property does not have this option, you may need to seek advice from your local water authority or have a containment and disposal solution installed.
Always ensure your backwash water is managed responsibly to protect the environment and comply with local regulations.
Common Mistakes to Avoid When Backwashing
Backwashing is a relatively simple process, but a few common mistakes can lead to problems later on.
First, many pool owners forget to use the rinse setting after backwashing. Skipping this step can cause dirt and debris to flow back into the pool. Another frequent error is backwashing too often, which can unnecessarily wear down your filter media and wastewater. Only backwash when your pressure gauge indicates a need.
It’s also important to remember that the multiport valve should never be turned while the pump is running, as this can cause internal damage. Always switch off the pump first, then adjust the valve.
Finally, don’t forget to monitor and top up your pool water after backwashing, as the process can significantly lower the water level.
How Often Should You Backwash Your Pool?
There’s no one-size-fits-all answer, but as a general guide:
- Sand or glass filters usually need backwashing every 1–2 weeks or when pressure increases.
- DE filters should be backwashed roughly once a month, with regular top-ups of DE powder.
- Always adjust your schedule based on usage, debris levels, and the behaviour of your filter system.
- A good routine will help keep your water sparkling and your system running efficiently.
Let Aquascape Help With Your Pool Maintenance
At Aquascape, we understand that pool maintenance can sometimes feel overwhelming, especially if you’re new to it. We offer comprehensive support, from one-off filter cleaning to fully managed pool care packages.
Whether you need help with backwashing, seasonal servicing, or installing an automated system to simplify your maintenance routine, our expert team is on hand to keep your pool in pristine condition all year round.
We also provide training and advice to give you the confidence to handle everyday maintenance tasks quickly. With
Aquascape, you’re never alone when caring for your pool.
Frequently Asked Questions
How long does backwashing a pool take?
The backwash cycle usually takes two to three minutes, followed by a one-minute rinse cycle. DE filters may require multiple shorter backwashes and rinses.
What happens if I don’t backwash my filter?
Over time, the filter will become clogged, reducing water flow, increasing pressure, and allowing debris to remain in the pool.
This can also strain your pump and other components.
Can I backwash too often?
Yes. Excessive backwashing wastes water and can reduce the effectiveness of your filter media. Only backwash when necessary, based on pressure readings.
Do all pool filters need to be backwashed?
Most sand, glass, and DE filters do. Cartridge filters, however, are cleaned manually and do not require backwashing.
Is backwashing different for indoor pools?
The process is the same, but indoor pools collect less debris so backwashing may be required less frequently.
