When searching for replacement hot tub filters, if you do not have the part number of the quality Darlly filters required, use our quick-to-use comprehensive ‘Find your filter’ helper pages in our online catalogue. By using measurements and by matching the thread type pictures, you should be able to find the quality Darlly filter you and your hot tub deserve.

You can use the dimensions that you have to help get to the required filter. How do you measure a filter? Easy! Follow our easy-to-use guide below showing how to measure the relevant dimensions and identify the thread type, if any. All measurements are in cm.

How to measure External diameter for a filter

This is the measurement across the filter from edge to edge. This example is 12cm.

How to measure hot tub filter Length

Measure the length of the filter but do not include the handle or thread.

How to measure internal/Inside diameter for hot tub filter

Different hot tub filter Thread and fitting types (bottom of filter)

There are number of different types of fitting and thread types available. Filters can have male and female threads which can be coarse or fine, and possibly tapered.

Photo shows male threads, fine on the left hand side and coarse on the right hand side.

Measure the thread diameter. This is the inner edges of the hole of the male thread. For a female thread, measure the inner diameter.

The Fine Thread (MPT) has from 6 – 8 fine twists (Pleatco ends P4 or F2M) whereas the Coarse Thread (SAE) will have as little as only 3 thicker threads (Pleatco ends P3 or F2S). 

Hot Tub Filter Male thread diameter measurement

Hot Tub Filter Female thread diameter measurement

Tops-From left to right- open (Hole), closed top, handle, removable lid handle

Now identify the top of your filter. Match it against one of the four main types shown in the photo to identify the type of top. 

If you know the name of your hot tub manufacturer, this can help too.

Now that we have this information, we can now delve into the Darlly website or online brochure ‘Find Your Filter’ pages. Nearly there!

There are a couple of ways to find the filter you need now, both from the home page of our website Darlly.eu (Hover above the FILTERS  dropdown then select the type of filter you are searching for)

The ‘Find your filter’ helper is on the left hand side now. Scroll down here to select any relevant details to search for your filter. If this doesn’t find your exact filter, take a look inside our latest online brochure.

Open the latest filter brochure from the home page on the Darlly.eu website. Scroll down to the ‘Find Your Filter’ pages then search with the information you have to identify your filter. 

If you have your hot tub brand, you can use this to narrow the search.

The main identification chart will enable you to identify the exact filter you have using the top, bottom, length and diameter measurements of your existing filter.

If you also have the filter manufacturers part number, you can cross check this with the part numbers listed against the appropriate Darlly filter.

To find your local Darlly filter stockist, click on ‘Stockist’ on the homepage and either enter address or zoom in on the map.

All genuine Darlly filters have the part number printed on the end cap (eg “60401”)

Also the label on the wrapper will have all details. (Please keep safe this for your next filter change) Pleatco and Unicel will also sometimes have the part number on the end cap. Our brochure and website www.darlly.eu contain all of the part numbers to help you. 

However, should you be without any part number after following the identification guide above and using our ‘Find a Filter’ guide using your measurements and brand identities, simply call us on +44 (0)1952 – 580500 we would be delighted to help you. 

Happy Hot Tubbing! 

The Darlly Team