If you’re not sure which replacement filter your spa needs, don’t stress. Spa filters come in all shapes and sizes, and it’s totally normal to feel a bit lost when it comes time to order a new one. Whether you’ve lost the original label, inherited a spa with no paperwork, or your old filter is too worn to read, we’re here to help.
In this quick guide, we’ll show you how to measure your spa filter properly and link you to our free PDF measuring guide to make it even easier. No guesswork, no wasted money on the wrong size.
Why getting the right size matters
Your spa filter does the heavy lifting when it comes to keeping your water clean. But if your replacement filter is even slightly the wrong size, it can cause issues like:
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Poor filtration
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Water bypassing the filter entirely
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Leaks or rattling
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Pump strain or damage over time
What you’ll need to measure
To find a perfect match, grab a tape measure and take note of these three key details:
1. Outside Diameter (OD)
Measure across the widest part of the filter, edge to edge.
2. Length
Measure the full length of the cartridge — but don’t include any handles, threads or fittings.
3. Connection Type
Look at the base of your filter. Is it a fine thread? Coarse thread? Slip fitting? Push-in? If you're unsure, our PDF guide shows examples of each to help you identify it.
How To Identify & Measure Your Spa Filter
We’ve put together a handy guide that walks you through the whole process , with diagrams, connection types, and tips to avoid common mistakes. You can print it out, take it to your spa, and even keep it on hand for future filter replacements.
Download HereWhat to do once you’ve got your measurements
Now that you’ve got the dimensions, you’re halfway there. Head over to our Spa Filters page and either browse by filter size or reach out to our friendly team if you’re unsure.
Spa Supplies stock a wide range of spa filters compatible with New Zealand spa pool brands, such as:
Still unsure?
If you’re stuck or just want a second opinion, flick us an email, give us a call on 0800 000 828, or send a photo to our team. We’re based right here in New Zealand and love helping spa owners get exactly what they need.