Domakihub How to Fit a Mains Water Filter in Your Home
Protect every tap in your property with a whole-house inline filter — here is what the job involves and when to call a plumber.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Installing a mains water filter — sometimes called a whole-house or point-of-entry filter — treats your water supply the moment it enters the building, so every tap, shower, washing machine, and appliance benefits. For properties in Greece, where municipal water can carry sediment, chlorine, and calcium, a good inline filter noticeably improves taste and protects pipework and appliances. The video above shows a professional plumber fitting exactly this kind of system; the steps below explain each stage so you can prepare the job, have an informed conversation with your plumber, or — if you are confident working on cold-water plumbing — tackle a straightforward sediment filter yourself.
What a mains water filter actually does
A point-of-entry (POE) filter sits on the cold-water rising main immediately after the stop valve and water meter. All water in the building passes through it before reaching any outlet. Depending on the cartridge type — sediment, activated carbon, or a multi-stage combination — it removes suspended particles, chlorine, taste and odour compounds, and in some cases heavy metals or hardness-causing minerals.
In Greek holiday rentals and hotels the most practical choice is a two-stage system: a 5-micron sediment pre-filter followed by a carbon block. It extends the life of downstream appliances (boilers, coffee machines, dishwashers) and is easy to maintain — cartridges need replacing every 6–12 months depending on usage and local water quality.
Is this a DIY job or a job for a licensed plumber?
Fitting a mains filter involves cutting into the main supply pipe, which means temporarily shutting off water to the whole building and making secure leak-proof joints. In Greece, work on the building's main water supply — particularly in apartment blocks or commercial premises — typically requires a licensed plumber (υδραυλικός) to ensure compliance with local regulations and insurance cover. If you own a standalone villa and are comfortable with copper or push-fit plumbing, a simple inline filter on an accessible rising main is within careful DIY reach.
The tasks described below are the standard professional sequence. Read through them before the plumber arrives so you can choose the right filter housing, agree on the installation point, and plan for future cartridge access — all decisions you should make in advance.
How to fit a whole-house mains water filter: the five key steps
- 1
Choose the installation point and shut off the water
Identify the rising main immediately after the stop valve and water meter — this is the only point where filtering every outlet makes sense. Close the main stop valve (usually at street level or inside the meter box), then open a tap at the lowest point in the building to drain pressure from the pipes. Confirm flow has stopped before cutting anything.
- 2
Cut into the supply pipe and fit the isolating valves
Mark a section long enough to accommodate your filter housing plus two inline isolating valves (ball valves), one on each side. Cut cleanly with a pipe slice or hacksaw, deburr the ends, and fit the ball valves. Having shutoff valves on both sides of the housing means you can replace cartridges in future without draining the whole system — this step is often skipped by inexperienced fitters and regretted later.
- 3
Mount the filter housing and make the connections
Screw the filter bracket to the wall or a vertical joist at a comfortable working height — you will need to unscrew the bowl every few months. Connect the inlet (marked 'IN') to the supply side and the outlet to the building side using the fittings supplied, typically compression or push-fit. Wrap all threaded connections with PTFE tape (three to four turns, in the direction of the thread) before hand-tightening, then use a filter-housing wrench to seat the bowl firmly without over-torquing.
- 4
Insert the cartridge, restore water, and check for leaks
Place the correct cartridge into the housing bowl — sediment cartridges are typically white polypropylene, carbon blocks are black. Hand-tighten the bowl onto the head. Slowly open the downstream ball valve first, then the upstream one, allowing the housing to fill gradually and avoiding water hammer. Check every joint for drips; a slow leak at a compression fitting usually needs just a quarter-turn more. Let water run at a nearby tap for two to three minutes to flush the new cartridge before using the supply normally.
- 5
Label the filter and set a cartridge-change reminder
Write the installation date on a label and stick it to the housing. Note the filter flow rate marked on the cartridge (usually measured in litres per minute) and compare it against your household demand — an undersized cartridge causes pressure drop. Set a phone or calendar reminder for the manufacturer's recommended change interval, typically six months for a busy rental property and twelve months for a lightly used private home. A clogged cartridge that is left too long can harbour bacteria, so this step is not optional.
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FAQ
- Do I need a licensed plumber to fit a mains water filter in Greece?
- For standalone private homes, a competent DIYer can fit a simple inline filter on an accessible rising main. For apartment buildings or commercial premises (rental villas operated as businesses, hotels, offices), Greek law and most property insurance policies require work on the main supply to be carried out by a licensed plumber (υδραυλικός). When in doubt, get a professional — the fitting cost is modest and protects your liability.
- How often should I replace the filter cartridge?
- As a rule of thumb: every six months for a property in constant use (rental, hotel, family home), and every twelve months for a lightly used holiday home. Greek municipal water tends to carry more sediment and chlorine than northern European supplies, so err on the shorter interval. A pressure drop at your taps is the clearest sign a cartridge is overloaded and needs changing immediately.
- What type of filter is best for Greek tap water?
- A two-stage setup works best for most Greek properties: a 5-micron sediment filter as the first stage (removing sand, rust, and particles) followed by an activated carbon block (removing chlorine, taste, and odour). If you are in a hard-water area — most of mainland Greece and the islands — consider adding a scale inhibitor cartridge or a separate water softener downstream. For drinking quality at the kitchen tap, an additional under-sink reverse osmosis unit on top of the whole-house filter gives the cleanest result.