Osmio Zero 2.0 Water Filter review

What it is, in plain numbers

Osmio rates the Zero 2.0 at 2,200 to 2,600 watts on a 220 to 240 volt supply, almost all of it the heater (2,180 to 2,580 watts), which it says delivers 30 litres an hour at 90°C or above. The filtering side is modest: a 50 gallon-a-day membrane that Osmio puts at up to 190 litres a day, or 7.8 litres an hour at 20°C, feeding a 1.5-litre reservoir from a 5-litre supply tank. Osmio lists it at 38 cm high, 18 cm wide and 41 cm deep (about 50 cm with the drip tray), and 7 kg.

The product page lists three quick-change stages: a composite carbon block, the reverse-osmosis membrane, and a post-filter of calcium and magnesium ceramic that Osmio says adds 10 to 20 ppm of minerals back; the manual adds a 5-micron sediment filter screwed into the supply tank. Osmio says to change the set every six months. It recommends the Zero for households of four people or fewer.

Living with it in a British kitchen

Every litre you drink is a litre you carried to it. Osmio is firm on one habit: tip out what is left before refilling rather than topping up. The machine recirculates the water the membrane rejects back into the tank, so dissolved solids climb with each pass and stale water can block the filters.

Hardness is the limit. Osmio recommends the Zero only up to 250 ppm calcium carbonate, expects mid-term carbon and membrane changes from around 200 ppm, and in the manual asks for a 3-litre fill rather than 5 above 280 ppm. For harder water it points customers to its plumbed Fusion or a softener. Check your water company's hardness figure first.

Heating is the running cost. On Osmio's figures, 30 litres an hour at 2,180 to 2,580 watts, each litre of near-boiling water takes about 0.07 to 0.09 kWh: roughly 2p a litre at the Ofgem price cap unit rate of 26.32p per kWh for October to December 2026, or about 57p to 68p for an hour of continuous hot dispensing.

How it compares

The nearest plumbed alternative on our site is the Waterdrop G5P700A: also reverse osmosis with a mineral stage, but mains-fed, rated at 700 gallons a day against the Zero's 50, with its own tap rather than a tank to refill. For no-plumbing convenience without hot water or RO-level purity, a filter jug or the Weeplow Earth gravity filter costs far less to run.

Maintenance, warranty and support

Budget for a full filter set every six months, a sanitising cycle before each change using Osmio's kit and Milton tablets, and a citric-acid descale every three to four months in hard water; each runs to nine steps in the manual. Left unused for more than two days, it wants a full cycle with the first batch discarded.

Osmio's product page gives a three-year warranty on manufacturing defects, handled as DIY repair or return to base. Limescale damage is excluded, as are skipped filter changes and cartridges that are not genuine Osmio parts.

Safety

The top setting dispenses water at 90°C or above, and Osmio asks owners to show everyone in the household how to use the boiling function safely and to keep the unit away from unsupervised children. Give it its own wall socket: the product page rules out extension leads and plug adapters, and says not to run another high-wattage appliance from a shared double socket while it dispenses hot water. A dry-run alarm locks out hot water if the heater overheats or runs empty.

Osmio's post-filter claim of 99% of bacteria and viruses is a maker's figure, not a certification, and the unit is no substitute for a boil water notice. UK tap water is already safe to drink; read is UK tap water safe first.

Our verdict

Buy it if you rent, cannot or will not drill, have water under 250 ppm hardness, and want both RO water and instant hot water in one footprint. Do not buy it if your water is harder than that, if you have a drain and socket under the sink, because a plumbed tankless unit gives more water for less upkeep, or for emergencies, because it stops the moment the lights go out.

Does the Osmio Zero 2.0 need plumbing?

No. It is a countertop unit with a 5-litre fill-by-hand tank, shipped with the filters fitted: fill, plug in, let it run its two-minute flush and pour away the first 5 litres. The only installation is a wall socket of its own.

Does the Osmio Zero 2.0 work in a power cut?

No. The pump and the heater both need mains electricity, so filtering and hot water stop together. Keep stored drinking water for outages, or a gravity filter, which needs neither plumbing nor power.

Is the Osmio Zero 2.0 suitable for hard water?

Only up to a point. Osmio recommends it for hardness up to 250 ppm calcium carbonate, with more frequent carbon and membrane changes and descaling every three to four months in hard areas. Above that it suggests its plumbed Fusion system or softened feed water instead.