Your first decision is to choose an original equipment (OEM) cartridge or a generic cartridge. OEM are reportedly a little more durable but cost up to 30% more that the generic brands. For the price and relative durability, most people will choose the generic cartridges when available.
If all the above information is available and readable that may be all you need. However, to be safe you should collect the following measurements of the cartridge: length - top plate to bottom plate; outside diameter (O.D.); and inside diameter (I.D.) where applicable. For the Hayward CF12002 the dimensions are L - 23-3/8", O.D- 8 15/16", I.D. - 4". Note: Make sure you measure these dimension accurately to the nearest 1/16".
Now access our site and click "Cartridges and D.E. Grids" in the left hand column. This category is the seventh down on the list. When you click it, this page will come up. Hit the return arrow to come back to this guide.
Choose either "Original Filter (OEM) Cartridges" or "Generic Filter Cartridges" and click on the filter manufacturer. We elected "Hayward" from "Generic Filter Cartridges" for our example. When you click it, this page will come up. Hit the return arrow to come back to this guide.
Now click the model of your filter. We picked Hayward C-1200 Generic Cartridge - number 22 on this list. When you click it, the webpage for "Hayward C-1200 Generic Cartridge" will come up. Half way down the page are the specifications for this cartridge including its measurements and end cap images. Hit the return arrow to come back to this guide.
Checking our cartridge measurement, we see that the length, outer diameter and inner diameter we measured above, all match the measurements shown half way down the website page for this cartridge.
We also compared our end cap designs and see that both top and bottom open ended match the description on the website page.
With matches on all the cartridge data, we are now ready to buy a replacements cartridge with reasonable assurance that the new cartridge will fit our filter. If you have any questions or some of this data is not available, give us a call.