A backyard swimming pool will probably be one of the largest investments most families will ever make, second only to the home itself. And with a financial outlay that large, careful consideration must be made to ensure the type of pool and equipment selected provide many years of carefree fun.
Types of Pool Filters
There are two popular types of filters for swimming pools: sand and cartridge. Both filters do an adequate job of filtering particles by cycling the water from the pool via a main drain and a surface skimmer, then pumping it through the filter and returning the clean water back into the pool. It is the manner in which the water is treated inside each filter that determines which may be best for you.
Sand filters have been around for decades and filter the water by flowing it through a media bed of fine granulated sand. The more sand, the cleaner the water becomes. In this case, therefore, bigger is truly better. Sand filters are easily recognizable as they are large spherical-shaped fiberglass globes with a valve and a bleed-off at the top of a plastic window for a view of the sand inside. Sand filters can work non-stop for days, if not weeks, before back washing is needed to clean and stir the bed of sand inside the filter. When pressure reaches a pre-determined point, the filter is stopped, the direction of the water flow is reversed, and the dirt and unwanted particulates are flushed away, usually onto a lawn or into the storm drain (a permit may be required).
A cartridge filter is much smaller than a sand filter, and is usually tall and narrow. Inside this filter are several paper filters that look like tubes. Pool water flows from the outside of these tubes, through the micro-sized pours, then is returned to the pool. Generally speaking, most consider cartridges to clean better than sand. As with a sand filter, when pressure within the filter reaches a certain level it's time for cleaning. But cleaning a cartridge filter is a much different process and takes longer than simply reversing a valve. The filter housing must be disassembled and each cartridge has to be hosed off by hand to removed dirt and debris.
Pros & Cons
Sand filters generally don't have to be cleaned as often and nothing has to be taken apart. Backwashing takes about 30 minutes and priming the pump is easily accomplished by bleeding the air from the filter.
Cartridge cleaning requires tools; a wrench or a screwdriver is needed and the filter housing has to be taken apart and reassembled. Cleaning the cartridges is a messy job and takes a considerable amount of time.
With proper backwashing, a media bed of sand can last years. Backwashing costs only the amount of water washed away. Cartridge filters, on the other hand, usually have to be replaced every year or so at a cost of around $200. Even though a sand filter doesn't provide quite the cleaning quality, many consider the ease of cleaning and the years of service a suitable trade-off.