Reverse osmosis (RO) is one of the most thorough household water-treatment approaches available, but “best” depends on the system design and your priorities.
The five things that matter most
01Membrane and stages: understand what happens before and after the RO membrane.
02Water efficiency: compare product-specific reject-water figures and how they are measured.
03Mineralisation: some systems add a remineralisation stage after RO; others do not.
04Maintenance: replacement intervals and costs can materially change ownership cost.
05Installation: countertop systems and plumbed-in systems suit different households.
Countertop versus under-sink
Countertop systems can avoid permanent plumbing changes and are often attractive to renters. Under-sink systems can be tidier at the point of use but generally require more installation.
Don't ignore the total cost
Build an annual ownership estimate using replacement filters, membrane replacement, electricity where relevant and water costs. A low purchase price can become less attractive if consumables are expensive.
Further reading
Start with what reverse osmosis is, then explore our countertop RO guide.