Plain English Shower Glossary by The Shower Doctor
We have compiled an A-Z glossary of most common shower types, accessories, spares, shower faults and other related information to help you make an informed decision when shopping on The Shower Doctor website. Scroll down to find the content listed alphabetically or use the links below to jump straight to a specific definition. We hope you find this glossary useful, but if you still have any questions, use the contact page to send us a message, or call our customer service helpline on 0131 538 4343 (Mon-Fri, 9am-5pm).
This page was last updated on 08.12.17
Also known as: wireless shower
Used in: gravity fed and combi boiler systems
Digital shower works in the same way as a traditional mixer shower, but the water flow and pressure are controlled by a digital processor rather than manually. They are installed without the mixing unit in sight (for example: in the airing cupboard, loft or under the bath) and controlled with a wireless remote.
Recommended digital shower videos:Aqualisa: How Digital Works
Also known as: instantaneous shower
Used in: all water systems
Electric showers heat the water inside and are usually connected directly to the mains water and electricity supply. They range from 7.5kW to 10.8kW (units 10kW and over require using heavy duty cables) in power. Higher kW rating means there is a more powerful heating element inside the shower delivering more hot water per minute. Visit our Fault Finder section, or watch the videos listed below to learn more about repairing electric showers.
Recommended electric shower videos:Shower Doctor TV: Electric showers explained
Replacing a part inside an electric shower
Electric showers YouTube playlist from The Shower Doctor
Also known as: heating can, can assembly
Used in: electric showers
Heating tank is used to heat the water inside a shower. Inside it, there are one or more metal elements (similar to those found in electric kettles) which can range from 7.5kW to 10.8kW in power. The more powerful the element, the quicker it heats the water up, resulting in higher water flow rate and temperature.
Typical signs of a faulty heating tank are tepid water temperature and low water pressure.
Recommended heating tank videos:Testing a heating tank element inside an electric shower
Also known as: mixing valve, blending valve, bath valve
Used in: combi boiler, pumped and gravity fed systems
Mixer showers blend hot and cold water inside. There are two main types of mixer showers: manual valves and thermostatically controlled mixing valves. Mixer showers come in a variety of designs, including built-in, exposed and bath valves. Some models come with diverters allowing for extra shower heads or body jets to be used during the shower.
Visit our Fault Finder section to learn more about common faults in mixer showers.
Also known as: gravity fed and low water pressure systems
Used in: gravity fed and low water pressure systems
Power showers take water from both the hot and cold water supplies and then mix it to reach your desired temperature. They have a blending valve (manual or thermostatic) and a small pump housed in the same case. This way, your shower can maintain high water pressure at all times, even when you live in an area with low water pressure.
Pressure Relief Device (PRD)
Also known as: pressure valve
Used in: electric showers, power showers
Pressure relief device is a safety valve found in all electric showers. It's typically a ball inside the outlet pipe or heating tank that gets ejected when the pressure builds up inside the shower. This is usually caused by a blocked shower head or a kinked hose.
Typical sign of a faulty PRD is water leaking from the bottom of the shower. If you require a new pressure relief device, visit our Spares section. You can learn how to replace it by watching videos below.
Recommended pressure relief device (prd) videos:Electric showers: A guide to pressure relief devices (PRDs)
Replacing Pressure Relief Device (part no.82800450) on a Triton T80z
Also known as:
Used in: gravity fed systems, mains pressure systems (for booster pumps)
Shower pumps boost incoming water pressure, and depending on their Bar rating (i.e. the amount of pressure they can produce), can serve one or multiple water outlets in your house - like a tap or a shower. If you live in an area with low water pressure, installing a pump can greatly improve your shower performance.
Recommended shower pump videos:Salamander Pumps: HomeBoost water pump installation guide
Shower Pumps: Servicing Salamander CT, CTXtra & CTForce pumps
Also known as: a coil
Used in: electric showers, power showers
Solenoid valve is controlling water flow to the shower. Inside it there is an electromagnetic coil with a plunger inside, which lifts up when energized, allowing the water to flow through to the shower. When the shower is switched off and electric current stops, the plunger deactivates and blocks the water flow again.
If the solenoid valve goes faulty, there is usually no water coming from the shower at all, or it just stops and starts. Very often, it's just the coil that needs to be replaced - you can watch the video below to learn how to test and replace it yourself.
Recommended solenoid valve videos:Electric showers: How to test and replace a solenoid coil
Electric shower problems: 5 most common faults
Thermal Cut Out (TCO)
Also known as: thermal switch
Used in: electric showers
TCO, or a thermal switch, is another safety device installed in electric showers. If the incoming water temperature or selected power setting are too high, the TCO will cut the power out and reset. If it cuts out too often, it fails completely and needs to be replaced.
A faulty thermal switch will have no continuity and will prevent the power getting to the
Recommended thermal cut out (tco) videos:Test and replace a Mira Sport 416.41 thermal cut-out (TCO)
Also known as: mixer cartridge
Used in: mixer showers, bar mixers, taps
Thermostatic cartridges use a wax or metal element inside to react to changes in temperature to mix hot and cold water.
Watch our videos listed below to learn more about shower cartridge repair and replacement.
Recommended thermostatic cartridge videos:How to replace an Aqualisa thermostatic cartridge
How to replace a Mira Excel thermostatic cartridge (part no. 903.33)
Testing a shower thermostat in less than 1 minute
Also known as: Water Regulations Advisory Scheme Approval
Used in: .
WRAS, or Water Regulations Advisory Scheme is put in place to ensure all water fittings like boilers, valves and showers, along with their internal components are of the highest quality and do not cause water waste or contamination. All water fittings which carry or receive water from public mains must comply with WRAS or Scottish Byelaws.
Find out more about WRAS Approval on the official WRAS website.