Point-of-Entry vs. Point-of-Use
Whole House vs. Under-Sink Water Filters
Should you filter all water at the main supply line, or just the kitchen tap? This comparison examines point-of-entry (whole-house) versus point-of-use (under-sink) filtration — covering coverage, exposure routes, cost, and which approach provides better health protection.
Why bathing water matters
Under-sink filters protect one tap. Whole-house filters protect your entire home. PFAS and chlorine enter the body through skin absorption and steam inhalation during showering — not just through drinking water. A single-tap filter leaves these exposure routes unaddressed. Research shows that dermal and inhalation exposure during a 10-minute shower can equal or exceed the chemical intake from drinking 2 litres of unfiltered water.
Mam Nature also offers a Kitchen Filter (€190) for single-tap use.
Side-by-Side Comparison
| Criterion | Whole House (Point-of-Entry) | Under-Sink (Point-of-Use) |
|---|---|---|
| Coverage | ✓ All water in the home Every tap, shower, bath, appliance, and outdoor connection receives filtered water. | – One tap only Typically the kitchen cold-water tap. All other water sources remain unfiltered. |
| Drinking water quality | = Filtered All drinking water taps are covered. | = Filtered (at connected tap) The connected tap delivers filtered water. Other taps do not. |
| Bathing water protection | ✓ Yes — showers, baths, all taps PFAS, chlorine, and other contaminants absorbed through skin and inhaled in shower steam are addressed. | – None Under-sink filters do not treat shower or bath water. Dermal and inhalation exposure routes remain unaddressed. |
| PFAS exposure routes | ✓ All routes (ingestion + dermal + inhalation) Whole-house filtration addresses all three documented PFAS exposure pathways. | – Ingestion only Under-sink filters only address PFAS ingestion through drinking water. Skin absorption and steam inhalation during showering remain unaddressed. |
| Appliance protection | ✓ Yes Dishwashers, washing machines, water heaters, coffee machines all receive filtered water. Reduces sediment and chemical deposits. | – None Appliances connected to unfiltered water lines are not protected. |
| Installation | – Professional (1–2 hours) Plumber installs at the main water supply line. One-time setup. | ✓ DIY (15–30 minutes) Most under-sink filters can be self-installed with basic tools. |
| Upfront cost | – €760+ (Mam Nature Essential) Higher upfront investment but covers the entire household. | ✓ €100–€500 Lower entry point. Single-tap coverage only. |
| Cost per litre (all water) | ✓ ~€0.002–0.004/L Calculated across full household water usage over 10 years. | – Not applicable Under-sink filters only treat kitchen water. Shower, bath, and appliance water remains untreated. |
| Filter capacity | ✓ 150,000 L/year (Mam Nature) Single annual cartridge change. | – 5,000–15,000 L per cartridge Varies by brand. Carbonit: ~10,000L. Grohe Blue: 600–3,000L. |
| Space required | – Main water line area Installed in utility room, basement, or technical cupboard. | ✓ Under the kitchen sink Compact. Hidden from view. |
| Maintenance frequency | ✓ Annual One cartridge change per year. | – Every 3–6 months More frequent cartridge changes due to smaller filter capacity. |
| Limescale treatment | ✓ Available (Mam Nature Water LIME) Optional salt-free limescale conversion for the whole house. | – Not available Under-sink filters do not treat limescale. |
Common Questions
Is an under-sink filter enough to protect my family?
An under-sink filter protects drinking water at one tap. However, research shows that PFAS and chlorine are also absorbed through the skin and inhaled as steam during showering — exposure routes that account for a significant portion of total daily chemical intake. For comprehensive protection across all exposure routes, whole-house filtration is necessary.
Can PFAS be absorbed through skin in the shower?
Yes. Research has documented that PFAS compounds can be absorbed through the skin, particularly during prolonged contact such as showering or bathing. Additionally, volatile compounds are inhaled in shower steam. These dermal and inhalation exposure routes are not addressed by under-sink or pitcher filters.
Is it worth upgrading from under-sink to whole-house?
If your primary concern is taste improvement at the kitchen tap, an under-sink filter may be sufficient. If you are concerned about PFAS, heavy metals, or chlorine exposure — particularly through bathing water — upgrading to whole-house filtration provides measurably more comprehensive protection and often lower per-litre costs over time.
Can I start with an under-sink and add whole-house later?
Yes, but they serve different purposes. Starting with a Mam Nature Kitchen Filter (€190) for immediate drinking water improvement is practical. When ready, a whole-house system (from €760) replaces the need for the under-sink filter entirely, as all water — including the kitchen tap — is filtered at the main supply.
What about using multiple under-sink filters at different taps?
Installing under-sink filters at multiple taps is more expensive and maintenance-intensive than a single whole-house system. You would still miss shower and bath water. A household installing filters at kitchen, bathroom, and laundry would typically spend more on hardware and cartridges than a whole-house point-of-entry system, while still leaving shower water unfiltered.
More comparisons
Start Filtering — Choose Your Level
From kitchen-only to whole-house protection. Mam Nature Swiss offers both options.