Your filter is your last line of defense in trapping debris on a constant basis and keeping it out of your pool. That’s why it is so important to use the right type and keep it operating as cleanly as possible. Each filter type has its advantages and disadvantages. The clarity you desire, the environment and your willingness to maintain the filter and its equipment will determine which type is best for you.
There are many factors that determine how effectively each filter can do its job, including filter area, water pressure and the size of the particles that it can trap. This ability is based on micron size. A micron is 1 millionth of a meter. In comparison, a human hair is about 70 microns across. A filter that traps particles about 5 microns wide will collect more material than one that traps particles between 25-30 microns. Below is a breakdown of the different types of pool filters and their benefits.
A sand filter is basically a large canister of sand that traps dirt and debris as water is forced through it. There are two types of sand filters used for pools. The most common is the high-rate sand filter, which uses sand as the filter medium. The other is a rapid-rate sand filter and uses layers of rock and gravel for support on top of the layer of sand. As water passes through the sand bed, dirt and debris are trapped by the sand grains.
Sand filters use 20-grade silica sand capable of trapping particles as small as 20-30 microns.
Maintenance: Sand filters are considered to be the easiest to maintain. Sand filters are backwashed when the pressure reads 10 psi over the normal operating level. With proper water chemistry, you can expect your filter media to last 5-10 years.
Cartridge filters use replaceable paper or fabric-like pleated cartridges as their filter medium. Cartridges have a large surface volume to catch whatever the water pushes through them. Depending on what style you choose, a cartridge filter may have one or more cartridges inside the tank.
Cartridge filters can trap particles as small as 10-20 microns.
Maintenance: Individual cartridges must be removed, sprayed and soaked when the pressure gauge reads 10 psi over the normal level. With proper maintenance, your cartridges will last 2-3 years.
Often called DE, diatomaceous earth is composed of the skeletons of microscopic sea creatures. This filter type is the most complex, but also the most effective. Because they can remove such small particles, they say DE filters “polish” the water as it passes through the medium.
DE filters work by forcing water through the diatomaceous earth, which traps the debris and algae. These upright cylinder tanks have long, half-moon, rectangular shaped grids or fingers. A spreader, which is connected to a collector or manifold, separates these grids and holds them in place. Water flows through the tank then passes through the diatomaceous earth. It then passes through the filter grids and finally into the manifold before returning to the pool.
DE Filters remove the smallest particles of any filter, from 3-5 microns.
Maintenance: Must be backwashed as with a sand filter when the pressure is 10 psi over the normal level. New DE powder must be added to the filter as well. DE filter media may last 10 years or longer depending on water chemistry and maintenance.
Discover ways to make the most of your pool—from the ABCs of Pool Care to DIY guides—in our How-Tos.