Filter Buying Guide

The filtering system (filter & pump) is the heart of your pool. It removes waste materials (leaves, suntan lotion, body oils, dust and dirt) from the water. It is also circulates the chemicals that sanitize the water and maintain clarity, and keeps the water temperature even throughout the pool. Here is a short overview of the types of filters and pumps available, including the benefits and drawbacks of each.

Sand Filters:

The oldest type of filter still used today, the sand filter has been the workhorse of the pool industry. Its design and operation is straightforward and simple. In the filter, water passes through a quantity of sand, which traps dirt particles. As the sand fills with dirt and debris, the water flow gradually decreases. When the filter needs to be cleaned, turning a valve reverses the flow of water and passes it out a waste valve, flushing the dirt away. This results in a loss of water, which must be replaced in the pool. The sand is replaced once per season.

The benefits of a sand filter are the low cost of sand and a simple mechanism that is easy to maintain. The drawback to sand filters are the loss of water during back flushing, and the fact that sand is the poorest filter media, removing nothing smaller than a 30 micron particle of debris from the water. Additionally, sand filters have the slowest flow rate of all the types of filters available, requiring longer running time.

Diatomaceous Earth Filters:

Diatomaceous Earth (D.E.) uses a very fine powder as the filter agent. Water pressure inside the filter housing causes the D.E. powder to cling to nylon grids, removing particulate matter as it passes through the powder before being returned to the pool. Cleaning is accomplished by "bumping" or wiping the grids with a built in cleaning rod, which knocks the D.E. and the dirt off the grids. The heavier dirt settles on the bottom of the filter, while the D.E. will reform on the grids. The benefits of the D.E. filter are that they do not need to be back washed, so there is no water loss. D.E. is the best of the filter media, removing a particle as small as 3 microns. (As a point of reference, D.E. will remove pollen particles from water). D.E. filters move a minimum of 2400 gallons per hour, more than twice than sand, allowing a shorter filtration time. The main drawback to a D.E. filter is it is more labor intensive than any other filter. After "bumping" the filter several times, it must be opened and cleaned, and new D.E. powder added. At the end of the season, the grids must be soaked in a solution of muric acid to prepare them for the following season.

Cartridge Filters:

Cartridge filters are the simplest of all filters, and the easiest to maintain. A pleated fiber filter, similar to the air filter on a car’s engine, is contained within the filter housing. The benefits of a cartridge filter are that they are virtually maintenance free. The filter element is removed every week or so and washed off with a hose or in a dishwasher, and replaced. It’s as easy as that. There is no filter media like sand of D.E. powder, and their flow rates are as good or better than D.E. filters. The main drawbacks are that they do not remove as fine a particle as D.E., the smallest being 15 microns, and the filter elements should be replaced every season, at a cost of between $50 and $100.

RECOMMENDATION: FOR ANY POOL LARGER THAN 18’, D.E. IS THE BEST CHOICE. IT WILL GIVE YOU SPARKLING CLEAR WATER, AND IS WORTH THE EXTRA WORK. FOR 18’ OR LESS, A CARTRIDGE FILTER WILL PERFORM FLAWLESSLY WITH NO EFFORT. IF YOU’VE OWNED SAND FILTERS BEFORE AND ARE COMFORTABLE WITH THEM, THEN BY ALL MEANS CONTINUE TO USE THEM, KEEPING IN MIND THAT MODERN TECHNOLOGY HAS RENDERED THEM ALMOST OBSOLETE.

Pumps / Motors

The pumps and motors used on the majority of pool filters are generally rated at 3/4, 1 or 1 1/2 horsepower. Horsepower rating is an indication of the flow capacity of the pump, but it is just one of the factors that determine quality and performance. Unfortunately, it is often the only specification quoted to the consumer. Other specifications such as torque and wire size may be better indicators of the pump's suitability for a specific pool. For example, the 1 hp pump Jacuzzi uses on its in-ground D.E. filter is almost twice as large as the 1 hp pump that is packed with its above ground filter. The increased wire size and greater number of windings make it better suited to handle the larger volume of water in an in-ground pool.

As a rule of thumb, a 1 hp D.E. filter/pump or a 3/4 hp cartridge filter/pump package is more than sufficient for all but the largest pools. Higher ratings are necessary only for 27’ round and 15’ x 24’ oval (or larger) pools.

You should "turn over" the water in your pool at least once per day. Most filters/pumps rate their flow in gallons per minute. To determine the time it will take to complete a filter cycle for your pool, take the gpm rate, multiply it by 60 minutes, and divide the result into the total gallons your pool contains. The following chart shows the typical times required for various pool sizes.