A filtered water tap delivers treated drinking water at the kitchen sink without filtering everything the house uses. There are three common arrangements, and they differ in how they are plumbed, how much they cost to install and how easy the cartridge is to change. Getting the choice right mostly comes down to how many holes your countertop has and what your water report says needs removing.
Dedicated tap alongside the main faucet
The traditional layout puts a small separate spout in a spare countertop hole, fed by an under-sink filter or a reverse osmosis unit. Its advantage is separation: the filter only treats water people actually drink, so a cartridge lasts far longer than one asked to handle dishwashing and pot filling as well. It is also the standard fitting for reverse osmosis, which needs its own outlet because the treated water is produced slowly. The trade is a second spout on the counter and a hole to drill if your sink or worktop does not already have one.
Three-way mixers and filtering faucets
A three-way tap combines hot, cold and filtered water in a single body with a separate internal waterway and its own lever, so filtered water never mixes with the untreated supply inside the spout. It looks tidier and needs no extra hole. Filtering faucets that pass everything through a cartridge inside the tap exist too, but they consume cartridge life on every rinse and pan fill. If you want one hole and honest filter economy, the three-way design with a separate waterway is generally the better engineering.
What the tap is actually connected to
The spout is only a delivery point. The filtration happens in the cartridge or system in the cabinet below, and that is what determines performance. A carbon block handles chlorine taste, odor and a range of organic compounds, and many are also certified for lead reduction. A reverse osmosis unit adds a membrane that handles dissolved contaminants such as nitrate, arsenic, fluoride and total dissolved solids, and it needs a drain connection and space for a storage tank. Pick the system for what your water contains, then choose a spout that suits the kitchen.
Installation details that decide whether you enjoy it
Check the cabinet has room for the housing plus clearance to swing a cartridge out, since a filter you cannot reach becomes a filter you never change. Use the isolation valve on the cold feed so servicing does not mean shutting off the house. Match the tap tail connections to your supply and confirm the countertop hole diameter before ordering, especially with stone worktops where drilling is a specialist job. If you are also treating the whole house, our whole house water filter guide explains how a carbon stage upstream extends the life of everything at the sink.
Hard water at a filtered tap
A filtered tap does not soften water, and a carbon cartridge leaves calcium and magnesium untouched, so kettles in a hard water area still scale up and glasses still spot. Reverse osmosis does reduce hardness minerals along with everything else dissolved, which is why kettle scale often vanishes on the filtered side of a kitchen that has one. If the goal is protecting appliances and plumbing across the whole house rather than improving one glass of water, that is a softener decision at the main line, not a tap decision.
Questions people ask about filtered water tap
Can I get filtered hot water from the same tap?
Some three-way and instant-hot designs deliver filtered hot water, but most filtered outlets are cold only. Cartridges are rated for cold service, and hot water arriving from the heater carries different chemistry than the filter was specified for.
How often does the cartridge need changing?
Follow the manufacturer's rated capacity and the calendar, whichever comes first. A dedicated tap sees low volume so cartridges usually last many months, but carbon degrades with time in service even when the volume figure has not been reached.
Do I need a new hole in my countertop?
Only for a dedicated separate spout. Three-way mixers replace the existing faucet and use the hole already there, which is the usual reason people choose them for a stone or composite worktop.
Does a filtered tap remove lead?
Only if the cartridge feeding it is certified for lead reduction, since ordinary taste-and-odor carbon is not. Check the model's listed contaminant reductions rather than assuming that carbon covers it.