Bathroom glossary

A back-to-wall WC is a toilet pan that sits flush against the wall or a furniture unit, with the cistern hidden behind it inside a frame or a fitted unit. Because the cistern and pipework are out of sight, it is easier to clean around than a close-coupled toilet and suits fitted bathroom furniture.

A basin waste is the fitting in the plughole of a basin that lets water drain away into the trap and waste pipe below. It may be a pop-up waste worked by a lever on the tap, a click-clack waste you press to open and close, or a slotted waste that lets the overflow drain through it.

Bathroom zones are the areas set out in BS 7671, the UK wiring regulations, that decide which electrical fittings can go where: zone 0 is inside the bath or shower tray, zone 1 is directly above it up to 2.25 m, and zone 2 extends 0.6 m beyond zone 1. Each zone sets a minimum IP rating.

A bidet is a low, basin-like fitting used for washing after using the toilet, usually with a tap or a rising spray. It needs its own hot and cold supplies and waste, and models with a spray below the rim need backflow protection under the water fittings regulations, so plan its position early in the design.

A cloakroom is a small downstairs room with a WC and a basin, often formed under the stairs, off a hallway or in part of a utility room. Compact and short-projection fittings make the most of the space, and a cloakroom without a window needs an extractor fan ducted to the outside.

A close-coupled WC is the most familiar type of toilet in UK homes, where the cistern sits directly on the back of the pan and the two bolt together into one unit. It is simple to fit and maintain because everything is accessible, though the visible cistern and pipework make it harder to clean around.

A combi, or combination, boiler heats water on demand straight from the mains, so there is no hot water cylinder or cold water tank in the loft. It gives mains-pressure showers, but its flow rate limits how many outlets can run at once, and any work on it must be done by a Gas Safe registered engineer.

A comfort-height WC is a toilet with a taller pan, so the seat sits higher than a standard toilet and is easier to sit down on and stand up from. It suits older people, tall people and anyone with knee or hip problems, and it is a common choice in accessible bathrooms alongside grab rails.

A concealed cistern is a toilet cistern hidden inside a wall frame, a boxed-in false wall or a fitted furniture unit, with only the flush plate or button on show. It pairs with a back-to-wall or wall-hung pan, makes the room look tidier and is serviced through the flush plate opening or a removable panel.

A Doc M pack is a set of accessible sanitaryware and grab rails laid out to meet Approved Document M of the Building Regulations, usually a WC, basin and rails in fixed positions for wheelchair users. Doc M packs are mainly required in public and commercial buildings, but the same principles help when planning an accessible bathroom at home.

Dual flush is a WC flush with two buttons, a smaller flush for liquids and a full flush for solids, which cuts the water used each time. Under the water fittings regulations a new WC must not use more than 6 litres for a full flush, and most new toilets now come with dual flush as standard.

An en-suite is a bathroom or shower room that opens directly off a bedroom, for the use of that bedroom only. Most en-suites have a shower, basin and WC rather than a bath, and forming a new one needs the drainage, ventilation and electrics planned to meet the building regulations.

An extractor fan removes steam and damp air from a bathroom to the outside, which helps prevent condensation and mould. In England, a bathroom fan must extract at least 15 litres per second when it runs intermittently, or 8 litres per second if it runs continuously, and the duct must end outside rather than in the loft.

First fix is the stage of a bathroom job before the walls are boarded and tiled, when the hidden pipework, waste runs, cable routes, concealed valves and cistern frames are put in place. Getting first fix right matters, because once the tiles are on, moving a pipe or cable means taking the finished surface off again.

A flush plate is the button panel mounted on the wall or furniture in front of a concealed cistern, used to flush the toilet. It usually has dual-flush buttons, and it can be removed to reach the valves inside the cistern for servicing, so it acts as the access panel as well as the control.

A freestanding bath stands on its own feet or plinth away from the walls, rather than being boxed in with a panel. It needs more floor space and a floor strong enough for its weight when full, and its taps are usually floor-standing or wall-mounted, so the pipe routes must be planned before the floor is laid.

A gravity-fed system stores cold water in a tank in the loft and hot water in a cylinder, and relies on the height of the tank to push water to the taps and shower. Pressure is often low, especially upstairs, so a shower pump may be fitted, which is allowed because the pump draws from stored water rather than the mains.

Grout is the filler pressed into the joints between tiles to lock them in place and keep water and dirt out of the gaps. It comes in cement-based and epoxy types and in many colours, and epoxy grout resists staining and water better, which makes it a good choice for shower floors and wet rooms.

A heated towel rail is a radiator made of rails that warms and dries towels and helps heat the bathroom. It can run on the central heating, on electricity alone, or on both with a dual-fuel element, and electric rails need an RCD-protected supply with the fused spur placed outside the bathroom zones.

A humidistat is a sensor that switches an extractor fan on when the humidity in the room rises, for example during a shower, and off again once the air has dried. It means the fan runs when it is needed without anyone having to remember, which suits en-suites and rooms that are used at odd times.

An IP rating is a two-digit code showing how well an electrical fitting is sealed against solid objects, the first digit, and water, the second digit. In bathrooms the water figure matters most: IPX4 resists splashing from any direction, IPX5 resists water jets and IPX7 survives immersion, and each bathroom zone sets a minimum.

An isolation valve is a small valve on the water supply to a single fitting, such as a tap, WC cistern or shower, that lets you turn off the water to that fitting without shutting off the whole house. It is turned with a screwdriver or a small lever and makes repairs and replacements quick and tidy.

A linear drain is a long, narrow channel drain set into a tiled shower floor or wet room, usually along a wall or across the entrance, with a slotted or tile-in cover. Because the floor only needs to fall in one direction towards it, large-format tiles can be laid with fewer cuts and a cleaner finish.

A macerator is a pump unit fitted behind a WC or other fitting that breaks down waste and pumps it through a small-bore pipe to the soil stack. It allows a toilet to go where gravity drainage is not possible, but the regulations only accept one where the home also has a WC on gravity drainage.

A mixer shower blends hot and cold water from your existing supply, whether a combi boiler, an unvented cylinder or a gravity-fed system, to reach the temperature you want. A thermostatic mixer holds that temperature steady when someone else uses water, and the valve can be an exposed bar or concealed in the wall.

Moisture-resistant board is plasterboard or cement-based board made to cope with damp conditions, used to line bathroom walls and ceilings behind tiles. It resists humidity but is not waterproof on its own, so the areas around a shower or bath still need tanking or a fully waterproof board before tiling.

An overflow is an outlet near the top of a bath, basin or cistern that lets excess water drain away safely before it spills onto the floor. On a bath or basin it connects to the waste, and on a WC cistern it usually drains into the pan, which is why a constantly running toilet often points to a faulty fill valve.

A P-trap is a trap shaped like a letter P lying on its side, where the outlet runs horizontally out through the wall rather than down through the floor. It is the usual choice for basins, baths and WC pans connected to a waste or soil pipe at the wall, while an S-trap outlet points downwards instead.

Part P is the section of the Building Regulations in England, and separately in Wales, that covers electrical safety in homes. In England, a new circuit, a consumer unit replacement or any addition or alteration to circuits in a room with a bath or shower is notifiable, so it must be done by a registered electrician or notified to building control.

Pillar taps are a pair of separate taps, one hot and one cold, each mounted through its own hole in a basin or bath. They give a traditional look that suits period bathrooms, but they cannot mix water to a set temperature at the spout, so many people now choose a mixer tap instead.

A pumped shower, often called a power shower, uses an electric pump to boost the flow from a low-pressure gravity-fed system with a cold water tank and hot water cylinder. The water regulations do not allow a pump to be connected directly to the mains supply, so pumped showers are only suitable for gravity systems.

An RCD, or residual current device, is a safety switch in the consumer unit that cuts the power in a fraction of a second if current leaks to earth, for example through a person or through water. Under BS 7671, every circuit serving a room with a bath or shower needs 30 mA RCD protection.

A riser rail is the vertical bar fixed to the wall that holds a handheld shower head, letting you slide it up and down to suit each user's height. It usually comes with a bar mixer shower kit, and some kits combine a fixed overhead head with the handset for rinsing and cleaning the shower.

Sanitaryware is the trade term for the main fittings in a bathroom: the WC, basin and bidet, and sometimes the bath and shower tray. Most sanitaryware is made from vitreous china, a glazed ceramic that is hard-wearing and easy to clean, while baths and trays are more often acrylic, steel or stone resin.

Second fix is the finishing stage of a bathroom job, after boarding and tiling, when the suite, taps, shower, furniture, lights, switches and accessories are fitted and connected. It ends with testing, silicone sealing and a clean handover, and it relies on first fix having put every pipe and cable in the right place.

Short-projection describes a WC, basin or vanity unit that sticks out less from the wall than a standard one, often by 100 mm or more. These fittings are designed for small bathrooms, en-suites and cloakrooms, where a little extra floor in front of the toilet or basin makes the room much easier to use.

A shower former is a pre-shaped board with the falls built in that sits in the floor of a wet room or level-access shower, guiding water to the drain. It replaces a shower tray, is tanked and then tiled over, and is set into or onto the floor so the shower is level with the rest of the room.

A shower tray is the waterproof base of a shower that collects water and carries it to the waste. Trays come in acrylic, stone resin and other materials, in square, rectangular, quadrant and offset shapes, and low-profile trays are only a few centimetres high, so they are easy to step onto.

Silicone sealant is a flexible, waterproof sealant run along the joints where a bath, shower tray, basin or worktop meets the wall or floor. It stays flexible as fittings move slightly with weight and temperature, and it should be replaced when it discolours, lifts or grows mould, before water can get behind it.

A soil stack is the large vertical pipe, usually 110 mm across, that carries waste from WCs and other fittings down to the drains and vents sewer gases above the roofline. Its position largely decides where a toilet can go, because a WC needs a short run with enough fall to connect to it.

A splashback is a waterproof panel or area of tiles fixed to the wall behind a basin or bath to protect the wall from splashes. It can be a few rows of tiles, a glass panel, an acrylic sheet or a solid-surface upstand, and it is the minimum wall finish to plan around any basin.

Tanking is a waterproof membrane or coating applied to walls and floors before tiling, so water cannot pass through the grout and tiles into the structure behind. It is essential in wet rooms and around showers, with sealing tape in every corner and around pipes and drains, because tiles and grout alone are not waterproof.

A thermostatic mixing valve blends hot and cold water to a set temperature and holds it steady even when the pressure changes, such as when someone flushes a toilet elsewhere. It protects against scalding and is the usual way to limit a new bath in a new home in England to 48 °C at the outlet.

A trap is the curved section of pipe below a basin, bath, shower or WC that stays full of water to block smells and gases rising from the drain. Common types include P-traps, S-traps and bottle traps, and baths and shower trays often use shallow traps to fit in the small space beneath them.

Underfloor heating warms a bathroom from below, using either an electric mat under the tiles or water pipes connected to the central heating. It frees wall space, keeps the floor comfortable underfoot and helps wet floors dry quickly, and an electric system in a typical bathroom costs £700–£1,500 supplied and fitted.

An unvented cylinder is a sealed hot water tank fed directly from the mains, so it delivers hot water at mains pressure without a cold water tank in the loft. It gives strong showers to several outlets at once, and it must be installed by a G3-qualified installer because of the safety devices it relies on.

A vanity unit is a cabinet with a basin set into or on top of it, giving storage underneath and hiding the trap and pipework. It can stand on the floor or hang on the wall, and it comes in widths from compact cloakroom sizes to double-basin units for family bathrooms and larger en-suites.

A wall-hung WC is a toilet pan fixed to the wall with nothing touching the floor, held by a steel frame hidden behind a false wall that also contains the concealed cistern. It makes a room look bigger and is easy to clean underneath, and the seat height can be set to suit the user when the frame goes in.

A waste pipe carries used water from a basin, bath or shower to the soil stack or a drain, usually in 32 mm or 40 mm plastic pipe. It needs a steady fall so water drains freely, and long runs or tight bends can cause slow draining, so the route is planned early whenever fittings move.

A wet room is a fully waterproofed bathroom where the shower is part of a level, tiled floor that falls to a drain, with no shower tray or step. The whole floor and the wet walls are tanked, and a wet room typically costs £6,000–£12,000 supplied and fitted, with compact rooms from about £4,500.