With hundreds of filters on the market finding a replacement filter for your spa can be challenging. We created this guide to help make finding a perfect replacement filter easier for you. The video below gives you an overview of two of the most widely used methods of finding a replacement filter. The article below goes more in depth so that you can have the knowledge you need to find exactly what you need.
There are two methods for finding a replacement filter for your spa. The first is either having a part number or finding it on the top of the filter. The second is by measuring the filter and searching for it by it’s dimensions.
Finding your filter part number Method #1
Some filters will have their part number stamped on the top of the cartridge such as in the picture below.
However not all things stamped on the filter are part numbers and you may need to use the filter measurement method covered next to find your filter.
A very important note on filter numbers:
Filter numbers change based on manufacturer. So there may be three or more different filter numbers that match your filter. A hot tub manufacturer number (Ex Hot Springs, American Whirlpool, Master Spas, etc) and each filter manufacturer (Ex Pleatco, Baleen, Filbur, etc) will have its own number for that filter.
Filter Number Example: Master Spas Eco Pur Charge is known by Master Spas as X268532 but is know by Pleatco Filters as PMA-EPR. These two filters are identical.
The important part is that the filter has the same features and dimensions as the one that came with the spa. We will cover more on features and measurements next.
Filter Measurement Method Method #2
The filter measurement method is the most reliable method. It requires two pieces of information, The filter length and diameter to begin the search.
If you are unfamiliar with how to read a tape measure watch the video from Andersen Windows below before reading further.
To find the length of your filter measure along the side of the filter from the top to the bottom end cap as shown in the example.
Always measure from the edge of the cartridge and do not include the handles, attachment points, etc on the top of the filter. The image below shows how to measure from the top end cap.
The red line shows you to ignore the other parts on the top of the filter such as the handle in this example.
When measuring the bottom end cap ignore any threads. The thick red line illustrates where the measurement should end.
To measure the diameter of the filter go across the center of the filter and measure from edge to edge. The edges are shown by the orange lines in the picture to the left.
- It’s important to consider that measurements may vary by about 1/16″ (one sixteenth of an inch) or 4mm. This is caused by expansion or shrinkage from use.
- For example, if you measure as a 5″ diameter, and can’t find a match, it may actually be a 4-15/16″ (four and fifteen sixteenths inchs) filter or 5-1/16″.
There are hundreds of filters on the market and you may see multiple results come up for the length and diameter you searched for.
You will need to compare the end caps features to find an exact match to yours.
The chart below shows all of the possible end caps on the market. Compare your filter to the chart to find out what type of end caps your filter has on the top and bottom.
We will go further in depth on end caps and threads next.
The bottoms end cap on a filter will be the one with threads if your filter has threads.There are two types of threads used in the hot tub industry, SAE or MPT.
For filters with male (External) threaded fittings, you will first need to determine the type of thread. There are two types of threads which are easily identified by referring to the left photo:
- Fine threads, also known as MPT or NPT
- Coarse threads, also know as SAE
Once you figure out what thread type you have you need to find your thread size.
Measure the outer diameter of the threads at the widest point. Then use the tables below to find your thread size.
|Measured Outer Diameter||Thread Size|
|Measured Outer Diameter||Thread Size|
(Internal) Coarse Threads
Measure at the widest inside diameter, not including threads.
This is known as the inner diameter for this type of filter.
Inner Diameter (open end caps)
There are a few kinds of open ended spa filters. They can be open on both sides as in the picture to the right. They can have a handle on one side and be open on the other, or it may be closed on one side with an open end on the other.
For these types of filters an important measurement is the inner diameter.
Measure the hole diameter from edge to edge ignoring any slots or tapered parts. Ignoring slots and taper will give you the smallest measurement for the inner diameter which is what you need.
On filters with an open end on one side and a closed end on the other there is an important thing to note. On the closed-top filters there may be a small pin-hole(s) to prevent trapped air from installing your filter from causing problems. Ignore these pin holes for measurement purposes.
Male Slip Fittings
Some filters have a non-threaded end that is called a slip fitting. For this type of fitting measure the overall outside diameter (O.D.) measured at the widest point as shown in the image.