Whole-House vs Under-Sink Filtration: Which Is Right for You?

If you’re weighing up a water filter for your home — whether you’re on town supply or tank water on a lifestyle block — the first decision is where the filter goes: at the point where water enters the house, or at the tap where you drink it. This guide explains both in plain language — what each does well, rough costs, and how your water source usually makes the decision for you. For a broader look, see our water filtration systems page.

What’s the difference?

Whole-house (point-of-entry): installed on the main line where water enters your home, so every tap, shower, appliance and hot water cylinder gets filtered water. Typically one or more large housings holding sediment and carbon cartridges, often paired with UV on tank or bore supplies.
Under-sink or bench-top (point-of-use): installed at a single tap — usually the kitchen — to treat only the water you drink and cook with. Under-sink units sit in the cupboard and feed a dedicated faucet; bench-top units simply connect to your existing tap.

Neither is “better” outright — they solve different problems, and plenty of homes run both.

Whole-house filtration: the case for treating everything

Protects your appliances and plumbing: sediment, rust and scale wear out washing machines, dishwashers, hot water cylinders and tapware. Filtering at the point of entry protects the lot.
Every tap is covered: showers, baths and the laundry all deliver the same clean water — not just the kitchen.
Essential on tank and bore supplies: roof water carries leaf litter and contamination from birds and possums, while bores commonly bring up sediment, iron and manganese. On these supplies a whole-house sediment and carbon setup — usually followed by UV sterilisation — is the standard approach, because you’re showering and brushing teeth in that water too.

The considerations: whole-house systems cost more up front, need to be plumbed into the main line, and use larger cartridges — typically 10″ or 20″ “big blue” sizes — to keep flow rates up. Undersizing the housings is the most common mistake we see; it chokes flow and shortens cartridge life.

Under-sink and bench-top filters: the case for treating just your drinking water

Low cost: a quality under-sink carbon system is a fraction of the price of a whole-house install.
Ideal on town supply: council water is already treated, so most townies just want the chlorine taste and odour gone — a single carbon cartridge at the kitchen tap does that job very well.
Simple to live with: cartridges are small, cheap and quick to change yourself, and bench-top units need no plumbing at all — a good option for renters.

The limits: a point-of-use filter does nothing for your shower, hot water cylinder or appliances, and a standard carbon unit isn’t a safety barrier against bacteria on an untreated supply — it’s a taste upgrade, not a treatment system. Browse our drinking water filters page, or see the under-sink and bench-top range at our online store, Pumps Online, on the compact water filter systems page.

Reverse osmosis: the step-up for drinking water

If you want the highest-quality drinking water — or need to deal with dissolved contaminants carbon can’t touch, such as nitrates, hardness or heavy metals — reverse osmosis (RO) is the step up. An RO unit fits under the sink but forces water through a fine membrane, removing the vast majority of dissolved solids. It produces water slowly into a small storage tank and sends some water to waste, which is why RO suits a single drinking tap rather than the whole house.

Decision guide: start with your water source

Town supply: an under-sink or bench-top carbon filter is usually all you need. Consider whole-house only if older pipes shed sediment or you want chlorine out of your showers too.
Tank or rain water: whole-house sediment and carbon filtration plus UV, since roof water can carry bacteria (E. coli indicates faecal contamination). UV needs clear water — pre-filter to 5 micron, ideally 1 micron, ahead of the lamp.
Bore or well: whole-house, sized to your water test. Iron, manganese, hardness and sediment are the usual suspects in Waikato bores; UV is recommended for shallow bores.
Mixed needs: combine both — whole-house for protection, under-sink or RO for the best-tasting drinking water.

What will it cost?

In broad strokes: bench-top and under-sink carbon systems start around a couple of hundred dollars; under-sink RO sits in the high hundreds to low thousands; a whole-house twin-housing setup runs from several hundred dollars plus installation; and adding UV typically takes a tank or bore system into the low thousands installed. Budget for consumables too — carbon cartridges are changed every 6–12 months, and UV lamps last about 9,000 hours (roughly 12 months of continuous running). Our guide to water filter changes covers the schedule.

Frequently asked questions

Can I have both a whole-house and an under-sink filter?

Yes, and it’s a common setup. The whole-house system handles sediment and appliance protection for the entire home, while an under-sink carbon or RO unit polishes the kitchen tap. Because the whole-house filters do the heavy lifting, the under-sink cartridges last longer too.

Do I need whole-house filtration on town supply?

Usually not for safety — council supplies are treated to the standards administered by Taumata Arowai, and most town-supply customers are happy with an under-sink filter for taste. Whole-house becomes worthwhile if you want chlorine out of your showers, or your area has sediment issues.

Will a whole-house filter reduce my water pressure?

A correctly sized system won’t noticeably. Pressure problems almost always come from undersized housings or clogged cartridges overdue for a change. Tell us how many bathrooms you have and we’ll size the system to your household’s flow rate.

Talk to the specialists

Still not sure? The Pump Warehouse team has been matching filtration systems to NZ homes for over 20 years. Call 0800 473 414, email sales@pumpwarehouse.nz, or drop into our Auckland (Rosedale) or Hamilton (Frankton) stores and we’ll spec a system on the spot.