What reverse osmosis actually does
The most thorough household filtration — with real trade-offs.
Reverse osmosis pushes water through a membrane with pores small enough to block dissolved solids. Where a carbon filter mainly improves taste and removes chlorine, RO also reduces nitrates, fluoride, sodium, arsenic and total dissolved solids. It is the closest thing to comprehensive filtration available in a home.
The three trade-offs nobody mentions on the box
It wastes water
RO sends some water to drain to flush the membrane. Ratios vary by system; efficient models waste far less than older ones.
It strips minerals
Calcium and magnesium go out with the contaminants. Some systems add a remineralisation stage to restore taste.
Do you actually need it?
For most Canadians on treated municipal water, no. A good carbon block filter handles chlorine, taste and lead for less money, less waste and less maintenance. Reverse osmosis earns its place when you have well water with nitrates or arsenic, high total dissolved solids, or water that simply tastes of minerals no carbon filter will touch.
If you are on a well, test first. Spending on RO before knowing what is in your water is guesswork — and some well problems, such as bacteria or iron, need different equipment entirely.
Maintenance you are signing up for
An RO system typically has several stages: sediment pre-filter, carbon pre-filter, the membrane itself, and often a post-filter. The pre-filters are changed most often; the membrane lasts considerably longer. Skipping pre-filter changes shortens membrane life, which is the expensive part. Budget for annual servicing.
Buying in Canada? Filters shipped from US retailers can attract provincial duties, taxes and carrier brokerage fees payable on delivery. Buying from a Canadian-fulfilled seller avoids those charges entirely.
Under-sink RO systems
Browse RO systems
Under-sink reverse osmosis systems available with Canadian shipping.
Prefer carbon instead?
If your water is municipal and simply tastes of chlorine, an under-sink carbon filter is cheaper and wastes nothing.
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