What Size Air Filter Should I Buy?

When it comes to buying an air filter, it's important to keep in mind that most disposable filters are discounted between ¼ and ½ of their standard size. To find the size of pleated filters used in your home, look no further than your existing filters. In the outer frame, you'll see at least one set of numbers. If you see two sets of numbers, the filter size needed to request replacements is the nominal size, not the actual size.

You can ignore the actual size printed on the filter for this task, since the nominal size is the set of numbers needed to order new filters. To determine the correct size of air filter for your home, start by measuring the length and width (L x W). If the filter is not square, the smallest measurement goes first. It's important to get the right size filter for your air conditioning unit, as gaps will allow dust, dirt and germs to bypass the filter and circulate back into your home. If you live in an older home with a non-standard size air return frame, you can use a foam weatherstrip tape to slightly increase the dimensions of your preferred filter or order a custom-sized air filter. When it comes to pool filters, there are several sizes available.

Smaller ones are suitable for above ground pools, mid-range ones can be used for small pools around 15,000 gallons, and large filters work best for pools larger than 25,000 gallons. No matter which pool filter you choose, remember that keeping your water chemistry balanced takes you more than half of a clean pool. When looking for a replacement air filter, start by reducing the depth of the filter. Note that the size shown in bold type on the filter frame is the nominal size of the filter, which is likely to differ from its actual size. If you could look at it with a microscope, you would see that it has a lot of small, rough edges around it, which is how it traps contaminants and debris that pass through the filter. It's not uncommon to see any filter material in the pool after backwashing, regardless of the type of filter you have.

If the filter is not the correct size, either too small or too large, air will flow around the filter instead of through it and, as a result, not all of the air will be filtered out. With all these factors in mind, make sure to find the right size air filter for your home.