If you've opened the cabinet under the sink and looked at how much space there is, you're already halfway there. An under-sink water filter is the choice for those who want filtered water at the tap but don't want to see anything on the counter.
The guide below goes step by step: what to measure, what to choose, how to install, and what to do after the first start. All with the real numbers of the Olympus filters, so you know from the start what you're getting into.
Before you start: what you need
Three things. A place in the cabinet under the sink for the filter body. A connection to the cold water pipe, which every kitchen has. And a small hole in the sink or countertop for the separate tap through which the filtered water comes out.
If you already have a Olympus countertop filter and want to move it underneath, there is countertop to undercounter conversion kit TO 46 €, without buying another filter.
Step 1: measure the space
The filter body stands upright or lies flat in the cabinet, next to the siphon. Measure the available height and depth and leave room for changing the cartridge once a year: the cartridge is removed vertically, so you need a few centimeters of free space above.
It's the step that most people skip, which is why we put it first.
Step 2: choose between single, double and triple
Here the decision depends on your water, not your budget.
The simple filter does complete filtering: Olympus undercounter water filter, 114 €, eliminates chlorine, pesticides, heavy metals, asbestos fibers, hexavalent chromium, arsenic, lead, cadmium and toxic substances, allowing mineral salts and trace elements to pass through.
Double filter add a second cartridge for retaining limescale or nitrates, of your choice: Olympus double filter for under the counter, 174 €.
Triple filter it makes both, limestone and nitrates, in the same system: Olympus triple filter for under the counter, 234 €.
If the limescale problem is throughout the house, not just in the drinking fountain, there is also water softener for central power supply, 178 €, which retains calcium and magnesium salts before the water reaches the appliances.
Simple rule: public water, with a chlorine taste, simple filter. Hard water, leaving deposits, double with a limescale cartridge. Well in an agricultural area, double with a nitrate cartridge or triple. If the water analysis shows complex problems, reverse osmosis is the next step.
Step 3: choose capacity
The standard Olympus cartridge has a service life of up to 12 months or 8,000 liters, suitable for a family of up to 5 people. For larger families or high water consumption when cooking, GIGA undercounter filter, 134 €, has a cartridge of 14,000 liters.
Both have the same ceramic activated carbon filtration, with pores ranging from 0.5 to 0.1 microns. The manufacturer recommends the 0.5 micron version, as smaller pores reduce flow.
When you choose GIGA
The standard model, with an 8,000-liter cartridge, is sized for a family of up to 5 people. From 6 people and up, or when you cook with filtered water every day, the GIGA makes sense: the 14,000-liter cartridge covers consumption without shortening the one-year interval between changes.
GIGA exists in the same configurations: simple at €134, and for limestone and nitrates together, GIGA triple filter for under the counter, 294 €. Filtration and antimicrobial protection are identical to the standard model, the only difference is the capacity.
Step 4: assembly
The under-sink filter is installed by yourself or with the help of a plumber, through a small diameter hole in the sink for the filtered water faucet. The body is connected to the cold water through a bypass valve, and the separate faucet is mounted on the sink or countertop.
The parts are available separately if you need them: undercounter faucet TO 15 €, connection valve TO 9 €. Step-by-step instructions are at Instructions for use.
If you don't want to make the hole in the sink, countertop filter does the same filtering without any intervention.
Step 5: First start-up and maintenance
After assembly, let the water flow through the filter before first use, as instructed. Then the only maintenance is changing the cartridge: once every 12 months or 8,000 liters, 14,000 for GIGA. The first replacement cartridge is included with purchase, and subsequent ones are at replacement filters Olympus.
Between changes, the filter takes care of itself: antimicrobial protection traps pathogenic microorganisms and destroys up to 95% of microbes inside the device within 2 hours, permanently disinfecting the internal chamber.
Cartridge calendar
Write down the installation date on a sticker on the filter body or on your phone calendar. The standard cartridge lasts up to 12 months or 8,000 liters, whichever comes first, and the GIGA lasts up to 14,000 liters. The first replacement cartridge is included with purchase, so the second year is already covered.
When the time comes, the change takes a few minutes: remove the old cartridge vertically, put the new one in, let the water flow.
Three checks before first start-up
The connections. After installation, turn on the water slowly and check each joint. A drip at first is solved with a squeeze, not with a bucket under the sink a week later.
Initial wash. Let the water run through the new cartridge according to the instructions until it runs clear. It is normal for the first few liters to look different.
Space for change. Before you close the cabinet door, take out the sample cartridge once. If you can take it out now, you can change it in a year.
How much does it cost in the long run?
The simple under-sink filter, €114, comes with the first replacement cartridge included. The next cartridge is 45 € to the standard model and 60 € at GIGA, at replacement filters Olympus.
Dividing €45 by 8,000 liters, filtration costs less than one cent per liter. This is a division by two figures stated by the manufacturer, not an estimate.
Why under the sink and not on the counter?
It's not a quality choice, the filtration is the same. It's a space choice and usually. Nothing is visible under the sink, the filtered water tap is permanently in place, and the countertop remains free. On the countertop, installation is simpler and does not require a hole.
All Olympus filters are manufactured in Greece by Center Plus SA, with a 2-year warranty and technical support. The quality parameters of tap water are those established by European Directive 2020/2184, and the management of water resources in Romania is in the care of National Administration of Romanian Waters.
Frequently asked questions
Do I need a plumber for the under-sink filter?
It can be installed by yourself, with the manufacturer's instructions, or by a plumber if you prefer. The only operation that requires tools is the hole for the separate faucet.
How much space does it take up under the sink?
The filter body plus a few centimeters of clearance above, for removing the cartridge when changing. Measure before ordering.
Can I switch from a countertop filter to an under-sink filter?
Yes, with the €46 conversion kit, without changing the filter.
What is the difference between double and triple?
The double adds a cartridge for lime or nitrate, of your choice. The triple includes both.
How often do I change the cartridge?
Once every 12 months or 8,000 liters on the standard model, 14,000 liters on the GIGA.
What are you doing next?
Measure your cabinet, look at your water and choose between single, double and triple. The rest is an afternoon's installation and one cartridge per year.
See all antimicrobial filters under the sink or start from choosing the right model.
