Domakihub Install an Under-Sink Water Filter in 5 Steps
Tap into your cold-water supply and add a dedicated filter tap — no more buying bottled water.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
The video above walks through a real under-sink filter installation, and the steps below translate that process into a practical guide for Greek homes, holiday rentals, and hotels. Municipal tap water across much of Greece is safe to drink by regulation yet carries enough mineral load and occasional taste issues to make point-of-use filtration the smarter long-term choice. Installing a dedicated filter tap under the kitchen sink takes about an hour and pays for itself within months compared to buying bottled water.
Why Greek Properties Benefit from Point-of-Use Filtration
Greece relies on chlorination and, in many island municipalities, desalination. Both processes leave behind residual tastes and odours that make tap water unpleasant to drink even when it meets EU safety standards. A quality under-sink carbon-block filter removes chlorine, sediment, and most taste compounds at the point of consumption, without affecting water pressure or the rest of the plumbing.
Holiday rentals and boutique hotels in particular benefit from offering filtered tap water as a guest amenity. It removes a recurring operational cost, reduces plastic waste, and is increasingly something guests expect — especially those arriving from Northern Europe where drinking from the tap is the norm.
What You Need Before You Start
Most under-sink filter kits ship with everything required: the filter housing, a mounting bracket, a dedicated filter tap, a saddle valve or push-fit T-fitting for tapping the cold supply, colour-coded tubing, and compression fittings. Check that your kit includes NSF/ANSI 42 or 53 certification on the filter cartridge — these are the standards that actually test for contaminant reduction, not just flow rates.
You will also need an adjustable wrench, a drill with a step bit or hole saw sized to your filter tap (typically 12–14 mm), plumber's PTFE tape, and a bucket and towels to catch residual water when you open the supply line. If your kitchen sink has a spare pre-drilled hole, you can skip the drilling step entirely.
How to Install an Under-Sink Water Filter
- 1
Shut off the cold-water supply and relieve pressure
Locate the isolation valve on the cold-water line under the sink — it is usually a quarter-turn valve on the flexible braided hose feeding the cold tap. Turn it fully clockwise to close, then open the cold tap above to drain residual pressure and water from the line. Place a towel or shallow tray under the pipe to catch drips.
- 2
Tap into the cold-water supply line
Most kits include a saddle valve that clamps around the existing cold-water pipe and self-pierces when tightened, or a push-fit T-piece that requires cutting a small section of pipe. The T-fitting method is more reliable and gives a cleaner seal: cut out roughly 20 mm of pipe, push the T-piece firmly onto both cut ends until you feel it click, then connect the filter inlet tube to the barbed port using the supplied compression nut. Wrap any threaded connections with two layers of PTFE tape first.
- 3
Mount the filter housing inside the cabinet
Choose a position on the cabinet wall or base that keeps the housing accessible for cartridge changes — you will need to unscrew the sump roughly every six months. Use the supplied bracket and the screws included in the kit. Position the housing so the inlet port (usually marked with an arrow or colour) faces up and connects easily to the tube running from your T-fitting. Hand-tighten the housing onto the head, then give it a quarter-turn with the filter wrench.
- 4
Drill for the filter tap and fit it to the sink
If your sink has no spare hole, mark a drilling point at least 50 mm from the edge and clear of any under-sink obstruction. Use a step bit to drill through stainless steel or a hole saw for ceramic sinks, working slowly with cutting fluid to avoid cracking. Feed the tap's supply tube down through the hole, secure the tap with the locking nut supplied, and connect the outlet tube from the filter housing to the tap's inlet fitting.
- 5
Restore the supply, flush the system, and check for leaks
Slowly reopen the isolation valve and watch every connection point for the first 60 seconds — saddle valves and push-fit T-pieces occasionally need a minor adjustment. Once no leaks are visible, open the filter tap fully and run water for three to five minutes to flush manufacturing residues from the new cartridge; the first water may appear grey or milky, which is normal carbon fines. Discard this flush water, then taste-test: filtered water should be noticeably cleaner and free of any chlorine smell.
Rather have a pro handle it?
Get a vetted plumbing pro in your city — one number, booked in EN/EL/DE.
FAQ
- How often do I need to replace the filter cartridge?
- Most standard carbon-block cartridges are rated for 3,000 to 5,000 litres, which translates to roughly six months of use in an average household. In Greece, high mineral content or heavily chlorinated municipal supplies can shorten that window to four months. Mark the installation date on the housing with a marker pen so you do not forget.
- Can I use the same filter tap hole for a mixer tap instead of drilling a new hole?
- Only if your current mixer tap setup leaves a spare pre-drilled hole in the sink deck — many four-hole sinks have one port free precisely for this purpose. If not, drilling is unavoidable. Do not try to share the cold-water hole with an existing tap by using a splitter; the resulting flow restriction will frustrate both functions.
- Is under-sink filtered water safe for guests in a holiday rental or hotel?
- Yes, provided the filter cartridge carries a recognised certification such as NSF/ANSI 42 (taste and odour) or NSF/ANSI 53 (health effects). Replace the cartridge on schedule and note the last change date in your property maintenance log. Displaying a small sign at the tap — 'filtered drinking water' — reassures guests and reduces your plastic waste in one step.