Bathroom taps: brass, PVD and ceramic cartridges — what to check before buying

On a tap display, most single-lever mixers look alike: the same silhouette, shine and handle. The difference between one that lasts for years and another that soon starts dripping lies in three details you cannot see in a photograph: the body alloy, the cartridge inside and how the finish was applied. Learning to check these points in the technical data sheet helps you choose on substance as well as appearance.

The tap body: brass versus zamak

The body is the housing that channels water and supports the handle, cartridge, spout, flexible connectors and fixing. Two alloys are particularly common in sanitary taps, and they behave differently.

A brass is a copper and zinc alloy, the traditional material for taps and still the benchmark for a simple reason: it performs well in contact with water. Copper gives it corrosion stability, it can be machined precisely, and its threads withstand repeated tightening and loosening without stripping. This matters because taps are dismantled to change cartridges, replace flexible connectors and clean aerators.

A zamak is a zinc alloy containing aluminium, magnesium and copper. It is easy to mould into complex shapes at low cost, making it common in decorative parts. Problems arise when it forms a body permanently in contact with water: zinc is more susceptible to galvanic corrosion and internal degradation that weakens the component. This can cause threads to strip after repeated tightening, distortion and small leaks in the body itself rather than at the seals.

Three clues help. First, weight: brass is much heavier for the same volume, so a suspiciously light mixer deserves a closer look. Second, the thread: brass threads look clean and the nut turns firmly; zamak may show burrs or play. The most reliable clue is the technical data sheet: manufacturers specify brass because it is a selling point. If the sheet says 'metal material' or omits the body alloy, that omission is informative.

None of this makes zamak inherently unsuitable: it works perfectly well in a handle or trim that carries neither pressure nor continuous water contact. The right question is which material forms the body, rather than whether the tap contains zamak.

The ceramic cartridge: the part that determines longevity

Inside every single-lever mixer is a cylinder operated by the handle that controls both flow and the mix of hot and cold water. This is the cartridge, and modern versions contain two ceramic discs polished extremely flat: one fixed, the other moving, with openings that overlap to different degrees as the handle moves. Greater alignment allows more water through; when they no longer overlap, the flow stops.

This explains the characteristic mixer feel: quarter-turn operation. There is no need for three full turns because nothing is compressed; two surfaces simply move against each other. These discs replaced the rubber washers in traditional taps, which shut off by pressing against a metal seat. Rubber hardens, cracks and eventually allows water to seep through. Ceramic is not compressed, wears much more slowly and is unaffected by temperature.

Cartridges are not universal, but are fairly standardised. The most common single-lever cartridge diameters are 35 mm and 40 mm, and knowing your tap's size can mean the difference between a ten-minute repair and replacing the entire unit. As a guide, 35 mm cartridges are common in basin and bidet taps, and 40 mm versions in larger bodies. Before buying, check that the manufacturer states the diameter and supplies replacements: a tap with no replacement cartridge is effectively disposable.

A worn cartridge gives warning signs before failing completely. The clearest are dripping when the handle is closed, hardness when moving the lever, especially from cold to hot, and noise: a new humming or knocking sound when opening. In most cases, the cartridge is replaced rather than the tap. Hard-water limescale accelerates wear; review your cleaning routine in our guide to removing limescale from taps without damaging the finish.

Finishes: chrome, PVD and paint

A finish is more than colour: it separates the brass from water, soap and cleaning products, and determines how much maintenance the tap needs each week.

A electroplated chrome is the classic finish and still offers excellent value for durability. It is applied by electrodeposition: the tap is immersed in a bath and electrical current deposits metal layers — nickel followed by chrome — onto the brass. The result is a hard, shiny, low-porosity surface that tolerates household cleaning well. Dried limescale and fingerprints show, but can be removed with water and a cloth.

A PVD (physical vapour deposition) works differently: metal is vaporised in a vacuum chamber and deposited on the component as an extremely thin, dense layer bonded almost molecularly to its surface. Compared with conventional plating, this provides greater hardness, greater scratch resistance and more stable colour. The process produces particularly durable gold, copper and black finishes, which is why premium coloured finishes tend to use PVD rather than paint. It is also more expensive to produce.

Matt painted finishes — mainly black and white — are coatings applied to the body, with a non-reflective appearance suited to contemporary design. They look excellent, but need careful maintenance: they are softer than PVD and sensitive to aggressive products. Acid cleaners, concentrated descalers, solvents and scouring pads can leave marks or shiny patches, and this damage is irreversible because the matt finish cannot be polished. Dried droplets are also more visible, requiring more frequent wiping.

In practice, finish affects maintenance as much as appearance. For hard water and minimal effort, polished chrome and PVD are advantageous; matt black or painted gold requires a more careful routine using neutral products.

Aerators and flow rates

The aerator is the threaded component at the spout tip. It mixes air with water to create a white, splash-free stream, filters particles carried by the plumbing and, on many models, limits flow. It is also the easiest tap component to maintain: unscrew it by hand or with the supplied key and clean it in a minute.

A flow restrictor is an insert that narrows the water passage and keeps flow fairly constant as mains pressure increases. The stream still feels comfortable because air compensates for the reduced volume, while consumption drops appreciably. As indicative information, a basin mixer without a restrictor typically delivers around 12 to 15 litres per minute at normal mains pressure, while a restricting aerator reduces this to approximately 5 to 8 litres per minute.

These values are indicative, rather than specifications. Actual flow depends on installation pressure, connection diameter and tap geometry, and identical taps in different homes can perform differently. Use them to compare approximate magnitudes. If flow suddenly drops in a previously functioning tap, start by cleaning the aerator: the cause is usually limescale in the mesh rather than a fault.

Shower hoses, flexible connectors and connections

Flexible connectors are the two hoses linking the tap to the hot and cold supplies. Quality versions have an outer stainless steel braid over a watertight inner tube: the braid reinforces it, absorbs water hammer and prevents expansion under pressure. This inexpensive component protects an expensive installation, so it is not the place to economise.

Bathroom connections usually have a male 3/8" thread at the isolation-valve end and a female M10 thread — the most common on basin and bidet taps — or M8 at the tap end. Before buying, check which connectors the tap includes and the thread on your valves: an unsuitable adaptor is a common cause of leaks beneath the basin.

Practical rule: replace the flexible connectors whenever you replace the tap. Even if the old hoses do not leak, their inner rubber has expanded and contracted through years of temperature cycles, so reusing it introduces unnecessary risk. During installation, avoid pulling them tight or bending them sharply near the thread: they should form a broad curve without tension.

Isolation valves shut off each fixture independently, allowing you to isolate a basin without turning off water throughout the home. Valves unused for years may seize; operate gently and replace any that resist movement or seep when changing the tap.

Choosing taps for each bathroom fixture

One bathroom may need four different tap arrangements. A costly mistake is choosing an attractive model without checking that it fits the existing fixture.

For a basin, spout height is decisive. A low tap is standard for inset basins; a medium-height model suits shallow basins; and a tall tap is designed for countertop basins: a low spout here directs water against the rim rather than into the bowl. Measure rim height, compare it with the stated outlet height and check that the spout reaches the centre of the bowl.

A bidet needs a dedicated short-spout mixer, usually with an adjustable aerator to direct the stream; many include an automatic waste. A bath needs a mixer with a diverter — the mechanism switching water from spout to hand shower — and the choice of wall-mounted, rim-mounted or freestanding installation changes the plumbing completely.

For a shower, first choose between concealed and exposed fittings. A concealed mixer hides its body in the wall, leaving only the control and outlet visible. It looks cleaner but requires building work and ongoing access for future maintenance. An exposed mixer sits on the tiles, can be installed without breaking them and is easy to replace, making it practical for partial renovations. A thermostatic shower column is a separate option: it maintains the selected temperature when pressure changes elsewhere in the home and includes a safety stop — usually around 38 ºC — to help prevent scalding. It is particularly suitable for bathrooms used by children or older people.

Common mistakes

• Choosing from a photograph rather than the technical data sheet. If the sheet omits body material and cartridge type, the information most relevant to the purchase is missing.
• Installing a low spout on a countertop basin. Water splashes outside or hits the rim, and replacing the tap is the only solution.
• Reusing old flexible connectors. Saving a few euros creates a risk of leaks beneath the unit and the resulting damage.
• Cleaning a matt or PVD finish with limescale remover or a scouring pad. Damage is immediate, irreversible and excluded from warranty.
• Not checking spare-parts availability. A tap without a replacement cartridge must be discarded when it starts dripping.
• Overtightening during installation. Soft bodies and threads can strip on the first excessive tightening; tighten firmly, without forcing.