Understanding When to Backwash Your Pool Filter

If you’re a pool owner in New Zealand, keeping your pool clean and running efficiently is a key part of maintenance. One important task is backwashing the pool filter, but how often should you do it? The answer depends on a few factors, including the type of filter you have, how often you use your pool, and the surrounding environment.

What is Backwashing?

Backwashing is the process of reversing the flow of water through your pool filter to flush out trapped debris and contaminants. Over time, dirt and debris build up in the filter, reducing its efficiency. Regular backwashing ensures your filter continues to function properly, helping to maintain crystal-clear water.

How Often Should You Backwash?

For pool owners in New Zealand, here are some general guidelines:

• Sand Filters: These should typically be backwashed when the pressure gauge reads 8–10 psi higher than the clean operating pressure. For most pools, this means backwashing every 1–2 weeks during peak swimming season.
• Diatomaceous Earth (DE) Filters: These require more frequent attention. You should backwash every 4–6 weeks, or when the pressure rises significantly. Unlike sand filters, DE filters require you to add fresh DE powder after each backwash.
• Cartridge Filters: These do not require backwashing. Instead, they should be cleaned manually every 4–6 weeks or when water flow decreases.

Factors That Affect Backwashing Frequency

While these are general guidelines, some situations may require more frequent backwashing:

• Heavy Pool Use – If you have a lot of swimmers, more body oils, sunscreen, and debris enter the water, which means the filter works harder.
• Surrounding Environment – Pools near trees or areas with high pollen levels may require more frequent cleaning.
• Algae or Cloudy Water – If your pool has been battling algae or cloudy water, you may need to backwash more often as part of the cleaning process.

Signs It’s Time to Backwash

Not sure if it’s time to backwash? Look out for:

• A rising pressure gauge reading (8–10 psi over normal).
• Reduced water flow from return jets.
• Poor water clarity despite proper chlorine levels.

How to Backwash Your Pool Filter

The process is straightforward:

1. Turn off the pool pump to prevent damage.
2. Set the filter valve to “Backwash.”
3. Turn the pump back on and allow water to run out of the waste pipe for 2–3 minutes, or until it appears clear.
4. Turn off the pump again and switch the valve to “Rinse.”
5. Run the rinse cycle for 30–60 seconds.
6. Turn the pump off, return to the normal filtration setting, and turn it back on.

If you’re unsure about backwashing your specific filter model, retailers like Para Rubber and Swimart have helpful resources and can provide advice on maintaining your system.

Tips for Efficient Pool Maintenance

• Try not to over-backwash your filter, as this wastes water and may reduce filtration efficiency.
• Use a pool cover when the pool isn’t in use to reduce debris.
• Test your pool water regularly with a kit from Pioneer Pool & Spa or Mitre 10 to keep chemicals balanced.

Final Thoughts

Backwashing is an essential part of pool maintenance, helping to keep your water clean and your filtration system running efficiently. By keeping an eye on your pressure gauge and understanding your pool’s needs, you’ll be able to maintain a healthy, sparkling pool all year round.