Availability of electricity
In areas with limited electricity, an RO or UV filter can be disappointing, especially if its purification speed is low. It is worth considering a filter with high purification speed or alternative non-electrical purification methods. A ceramic filter can be a worthy alternative.
Availability of water supply
If the water supply is already scarce, it might not be wise to use an RO filter (Drink Filtered) which wastes water proportional to the concentration of impurities, although the discarded water can be harvested for other uses such as cleaning vehicles and watering plants. Furthermore, it is advisable to keep RO filters off when there is no water supply, because the motor’s attempts to draw water constantly when there isn’t any available leads to premature burnout, requiring a not so cheap replacement, which introduces the additional overhead of keeping track of water supply.
This is more relevant if electricity and water supply are available for limited duration and consumption is high in comparison with the resultant rate of filtration. It can be cumbersome to store water elsewhere frequently in order to empty the filter container for more filtration.
Initial and maintenance cost
Reverse osmosis filters are the costliest in terms of initial and maintenance costs. Ultraviolet filters can be purchased at half or one-third of the cost of RO filters, and are low maintenance as well because fewer and less expensive parts need to be replaced with use. Ceramic filters are more economical in comparison and ultrafiltration faucet attachments are dirt cheap.
However, it is strongly advisable to not skimp on water purification and compromise on quality, because the health consequences of unfit water consumption can be far-reaching and more expensive in the long run. If a good quality filter is not affordable, boiling and chlorination are inexpensive and relatively simple alternatives.
Condition of unfiltered water
UV filters kill microorganism with ultraviolet rays, however, their dead bodies remain in the water. Also, they have no effect on dissolved salts and heavy metals such as lead, arsenic. It makes them unsuitable for water with high TDS (Total Dissolved Solids) readings. An RO filter is best suited here, because it filters out microorganisms as well as the majority of dissolved solids, giving soft and tasteless water. Ultrafiltration systems are usually faucet mounted and as water runs through them, they filter out germs but not salts. They are best suited for water that is already quite soft.
Ease of use and maintenance
Ceramic filters can be the most inconvenient to maintain because they frequently need to be cleaned cautiously for them to work optimally. Faucet mounted UF filters are can handle rough use, although they require manual cleaning as well. Wall mounted RO and UV filters require little to no upkeep from the user. Under the sink, purifiers can have only a faucet visible above the counter which is neater.