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You are here: Home > Spa and Leisure 101 > How to Find a Replacement Spa or Hot Tub Filter
How to find a replacement spa or hot tub filter

Finding a replacement filter for your spa or hot tub in 6 easy steps

The two methods of finding replacement filters

The two ways to figure out which filter will fit your hot tub (spa) are by part number and by measurement. The part number method makes the filter search easy. Some manufacturers will print their part number on the top endcap of the filter for your convenience. You can try searching for this number, however sometimes this number will not bring up your filter in a search. It doesnˈt hurt to try it just in case it is that easy. If there is not a part number present, or the part number does not yield any results then the measurement method is the next best choice. The measurement method is extremely effective at helping find replacement filters. However there are a few steps to take to gather all of the information it requires.

The measurement method

The measurement method requires you to find your filterˈs end cap configuration, length, and Outer Diameter (OD). Some filters will also require you to find the Inner Diameter (ID). For this take all measurements in inches as accurately as possible. The things you will need are a measuring device and your current filter. We recommend using a tape measure for this, however a ruler will work in some cases. The best place to start is to identify your end cap configuration.

End caps 101

You will need to know what types of end caps are on each side of your filter. The chart in the infographic can help you identify which types you have. If you have a threaded fitting on your filter there are two types, fine and course. Fine threading will be small and close together and course threads will be large and spaced apart. On some filters fine threads are also called MPT or NPT and coarse threads are also known as SAE. The next thing you will need is the filterˈs length.

Filter length

Measuring a filterˈs length is often the most confusing part of this process. The confusion arises because the idea of length immediately brings to mind the measurement of the total length. By total length we mean from the furthest end on one side to the furthest on the other including the threaded extension and the handle (if one or either exists). For this measurement you only need the length of the cartridge from the outside edge of one end cap to another as shown in the infographic. Manufacturers do not include any handles or fittings in their measurement specifications and adding them in your measurement will give you the wrong filter every time. This measurement may also be off, on a used filter by as much as 1/8th of an inch from the original filters measurements due to expansion and contraction during use. The last measurements needed is/are the filterˈs diameter(s).

Measuring the diameters

The Outer Diameter (OD) is a measurement all filters will have. However the Inner Diameter (ID) is only on filters with an open end cap style which will have a circular hole in the center of the endcap. The Outer Diameter (OD) is measured by using the full diameter of the filter as depicted in the infographic. This measurement should be taken through the widest part of the filter if possible. On endcaps with handles, measure along the handle to get the closest measurement you can (when searching using a handle measurement, it may be slightly shorter than the filters shown). To measure for an Inner Diameter (ID) if you have an open style end cap; measure from one inside edge to another across the widest part of the opening.

How to search for a replacement filter

By following all of the steips above you now know all of the measurement you need to find your replacement filter cartridge. At his point you may be saying ʺok, I have the measurements. Now where do I go and how do I look up my filter?ʺ To do this you only need to click ʺ Hot Tub Filters by Size.ʺ From here you will be able to click on the outer diameter and then the length category your filter falls into. From here the filters will show pictures and dimensions to help you find the one you need. Just remember that ID is Inner Diameter and OD is Outer Diameter. This leaves the last topic to be discussed, filter options.

Filter options

As promised earlier we said that we would go over the options with you. There are many out there but we only offer two. We offer basic filters and Microban treated ones. The Microban treatment inhibits the growth of bacteria and other microorganisms on the filter. These organisms can cause stains, odors and cause your filter to prematurely deteriorate. Through going on the defense against these organisms with the Microban option, you are extending your filters lifespan, preventing the growth and circulation of microorganisms that your spas chemicals will later have to deal with, and making filter maintenance easier. When searching for these filters look for all blue filters in the pictures and the -M in the part number. If this is not something you are interested in you will want to look for the filters with the white pleats and no -m in the part number for a basic filter.