You might be in the process of designing your swimming pool or perhaps you are deciding on a replacement filter for your swimming pool.
If you have a residential swimming pool, you are probably going to want either a cartridge or a DE type of filter. Sand filters are primarily for high-use commercial pools.
Here are some things to consider if you are trying to choose between a cartridge and a DE type of filter:
Water Quality – In most cases you cannot tell the difference in water quality between the two types of filter, but technically DE filters do filter a bit more finely.
Ease of Maintenance – Cartridge filters are way easier to maintain. No monthly backwashing. Easier to take apart and clean every six months. No filter powder to remember to add.
Cost of Maintenance – The maintenance costs on a cartridge filter are typically much lower. No DE to buy, no broken grids or manifolds to replace.
Energy Efficiency – Cartridge filters produce less resistance to flow, so you can get more water flow with a lower HP pump, thereby saving energy
Handling Green Water – With a DE filter, if your pool turns green, you can fairly quickly backwash and get the water flowing again. If you have a cartridge filter, have no choice but to break the filter down and clean it manually to remove the green algae from the cartridges.
Water Efficiency – Since a cartridge filter does not require backwashing, you don’t waste thousands of gallons of water each year in the backwashing process
Once you have decided on the type of filter that you want, you have to make a choice between the various sizes of filter.
There are really two criteria to consider:
Flow Capacity – you need to have a filter that is properly matched to the flow that the pump will produce. It is important to remember one key fact: The slower the water passes through the filter media, the better that it filters out. You can push a lot of water through a small filter, but that does not mean that it will filter very well.
Dirt Loading Capacity – you need to have a filter that can hold all of the debris that it will trap between maintenance visits.
Once a filter fills up with trapped dirt and debris, the flow is greatly reduced through the filter and the overall circulation rate of the pool drops way down. If you have a pool that catches a lot of dirt and debris, you should opt for a larger filter.
A 100 square foot single cartridge filter will handle 60 gallons per minute of flow, but will not hold very much debris. You would probably have to clean that cartridge at least monthly. If you had a 460 or 580 square foot filter, you would probably go six months between filter cleans. The smaller filter might save a few bucks, but the larger filter will be a LOT less hassle.
*Be careful about matching a DE filter with anything larger than a 2.0 HP pump. It can work, BUT if the filter pressure goes up and you do not backwash on a timely basis, your pump has the capacity to crush the grids. The larger the pump, the quicker that this can happen.