Many customers ask me what is the best pool filter for their needs. Pool filters come in three varieties: cartridge, sand and diatomaceous earth. The fact is that all of these filters do a decent job of filtering the water – but each has its own advantages and disadvantages.
A cartridge filter will only filter out large particles of dirt. For finer filtration, you need a sand filter – and for the finest filtration available, you should go with a diatomaceous earth filter.
One disadvantage of a cartridge filter is the hassle of having to physically remove the cartridge and hose down the filter. Manufacturers’ instructions have you soak the filter in trisodium phosphate (TSP). To follow those instructions, you would need to have two filters on hand – one to operate the pool and the other to be soaking in a garbage can filled with solution of diluted TSP. Very few cartridge filter owners are willing to go through this extra step.
The sand filter is actually the perfect compromise between ease of use and particle size filtration. This filter will trap a particle size smaller than the cartridge filter – but not quite as small as the diatomaceous earth filter. The main advantage of the sand filter is that there is no need to hose off a cartridge. You simply turn the multiport valve to backwash and flush the system. One very important note – and a common mistake that most customers make – is failing to turn off the pump before they begin to rotate the multiport valve. Attempting to change the position on the multiport valve with the pump running will impinge the gasket – and this will cause the valve to leak.
The diatomaceous earth filter will filter out the finest particles of dirt. The only hassle with using this filter is that at each backwash cycle you need to add extra DE powder via the skimmer.
I should also mention that there is an innovative new product called Zeobrite that improves the filtration and ease of use for sand filters. If you are purchasing a new sand filter, Zeobrite can be added while the filter is being assembled. It is much more difficult to add Zeobrite to an existing filter – so this is probably something best left to a service technician. However, the advantage of Zeobrite is it will last longer than sand and filter out particles as fine as if not finer than that of a diatomaceous earth filter.