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Plumbing Jargon Buster

When plumbing work is taking place at your property, you may hear your plumbers talking in a vocabulary you simply do not understand – it can seem like another language, almost! Unless you have been shopping thoroughly for plumbing supplies or are thinking about looking at plumbing courses, it may never have crossed your mind to look at the technicalities of the world of plumbing in more detail.

This is where Conwy Valley Plumbing and Heating steps in. We are experts in plumbing supply and installation. We have been working here in the North Wales area for many years now and have installed many fantastic bathrooms, kitchens, boilers and central heating systems for many extremely satisfied customers. We strive to offer our customers with economical and energy efficient products which save them money through their utility bills whilst improving their homes and carbon footprints.

So, you might not know your bleed valve from your cistern, or your combination boiler from your conduit. Have no fear; the Conwy Valley team is here! The following jargon buster will help break down the language barrier the next time you need to speak to us. So the next time we visit your home in order to complete a quick and easy fix, we’ll get your home running smoothly without boggling your mind.

Actual capacity

The amount of water contained in a cistern when it’s full to its practical level.

Above ground drainage system

A system of pipework which is used to remove foul water or rainwater to the drainage system.

Above ground sanitary pipework system

A system of pipework which conveys the discharge from sanitary appliances.

Abutment flashing

A weatherproofing material which is used to seal the join between a rood and a brick wall. For example, it could seal the joint between the garage and an external brick wall.


A blockage in water pipes that is caused by air being trapped. Water may splutter through the pipes, flow too slowly or even stop flowing altogether. This can affect any other pipes, taps, radiators or other appliances which are connected. Trapped air enters the system due to a number of different reasons such a damaged pipes and poor poor plumbing. An airlock may result in you needed professional help.

Air brick

A purposely designed brick which has fixed ventilation openings that allow air to pass through. This ensures that there is a proper combustion of open-flued combustion appliances and adequate ventilation which helps to prevent rot in suspended timber ground floors.

Ball valve

A valve which is operated by a ball that floats on the surface of water. This is what is found in toilet cisterns and what is used to control the flow of water. After you have flushed the toilet, the cistern empties and the float then drops which causes the valve to then open, letting water flow in. When the toilet cistern fills, the ball rises, when the the tank becomes full, the ball closes the valve.


Bidets are used for cleaning the excretory organs of the body with either hot or cold water.

Bleed valve (radiator)

This is the value which is located at the top corner of your radiator. When opened it allows trapped air to escape. Trapped air stops heaters from working properly when it should be filled with hot water. Releasing the air generally fixes this issue, and if it doesnt, you know who to get in contact with!


A tank which is used to store water, such as the toilet cistern.

Combination boiler

A Combination boiler or a combi boiler is an efficient and compact boiler which provides heating and ‘on demand’ hot water. Cold water is supplied directly to the boiler from the mains supply and is heated when it is needed. Combi boilers are very popular because they save lots of space; they don’t require a cold water store in the loft or hot water cylinder in the airing cupboard.


A tube or tunnel that pipes pass through.


This is the drainpipe which runs down to the drain from a gutter.


This is a fitting which connects two pipes at an angle of 45 or 90 degrees. Elbows can use compression or solder joints.

Feed and expansion cistern

A cistern which is used for supplying cold water to a hot water or a heating system. They are also used for open vented central heating systems and indirect hot water systems.


A duct or passage that is designed to simply carry harmful gases away, a chimney for example.

Flow rate

The quantity/volume of water that is delivered to a tap or an appliance in litres per minute (l/m) or litres per second (l/s).

Gate valve

These are generally used on low pressure pipework for isolation purposes.

Hard water

Water which contains a high level of calcium salts. Temporary hard water, when heated deposits the calcium salts onto various components in a system causing ‘furring up’. Hard water is alkaline.

Immersion heater

The immersion heater is a heater which is directly attached to a water tank. The electrical element heats up the water supply. The water can be heater overnight when electricity tends to be cheaper and then used during the daytime.

Indirect cylinder

A hot water storage vessel which is used on an indirect hot water system. The cylinder is used on an indirect hot water system and has an annular coil inside which forms parts of the primary circuit.

It will be heated by a boiler, with the possibility of an immersion heater as a secondary source of hot water.


This is the insulation which is wrapped around hot water cylinders, pipes and tanks in an effort to prevent heat loss and freezing during the winter.

Nominal capacity

The amount of water which is contained in a cistern when it is full to the top edge.

Mixer tape

This is one tap which allows hot and cold water to flow through it. This can mean both together for different temperatures or separately.

Pressure reducing valve

A pressure reducing valve is fitted to the incoming cold water supply so that the water pressure can be reduced as and when it is needed.

PTFE tape

This is tape which is used for sealing pipe threads*. The tape is wrapped around the thread before it is screwed into place. PTFE tape is used regularly on pressurised systems such as central heating, it acts as an enhanced seal and reduces friction. This tape can be wrapped around two pipes that screw together at either end of a radiator.

(*A thread is the section where two things are screwed together such as a nut and bolt.)

Primary circuit

As assembly of water fittings which water circulates between a boiler and a primary heat exchanger inside a hot water storage vessel.

Push-fit joint

This is a type of fitting for connection two pipes or more. The seal is made by pushing the pipes into either end of the fitting. This is the simplest technique for joining pipes as no soldering or tools are required like with compression or solder joints. This makes push-fit joints ideal for any DIY although the seal isn’t as reliable as other plumbing methods.

Quarter turn ball valve

A quarter turn ball valve is used inside a property as an isolating or servicing valve. The lever action enables the user to very quickly and easily isolate the water supply that is turned off using a flat blade screwdriver.

Servicing valve

These are installed near appliances such as cisterns for the purpose of individual isolation in order for maintenance to take place.

Silicon sealant

Silicon sealant is a gel which is used to seal the joints around baths, sinks and any other areas that are in need of protection from water.

Sink or sink unit

You will normally found a sink fitted in a bathroom, kitchen or a utility room. They are used for washing up, cleaning vegetables and other preparation activities. There are many specialist sinks available which are unique benefit from practical features.

Soft water

The water which falls on moorland which tends to be pleasant for washing activities, it can though lead to corrosion problems.

Soil pipe

A drainpipe which carries waste from a plumbing fixture, such as a toilet for example.

Solder joints

Solder joints are the traditional fitting for joining two or more copper pipes using a flame touch and flux. The flux is coated onto the joints before being heated to form a seal. This is more complicated than compression or push-fit joints as it requires more skill, meaning it is not suitable for DIY.

Although it is not suitable for DIY, when completed by a professional, it makes for a very reliable joint.


A stack is a vertical pipe which carries waste away from sinks and toilets.


A device which regulates temperature and which is used on central heating systems.

TRV (Thermostatic Radiator Valve)

This controls the temperature of one individual radiator. The TRV is the circular shaped device on the side of your radiator which you twist in order to adjust the heat.

U Bend

The U bend is the U shaped pipe which is located under the plug hole of sinks and baths. The shape of the pipe allows water to be retained, preventing air and horrible smells from the sewer passing through. U bends are widely used in the design of toilets in the United Kingdom.

Vent pipe

This means a pipe which is open to atmosphere, opening up the system to atmospheric atmospheric pressure at its boundary.

Water softener

Uses for changing hard water to soft water, the softening process involves the addition of common salt.

There are many terms in plumbing and it can sometimes seem hard to get your head around if you are new to it. Hopefully we have gone some way to improving your knowledge of the parts and components that you may come across. All the terms we have covered in our plumbing jargon buster are widely used in the United Kingdom by plumbers, and if you work with us, you will hear our team speaking at length about these terms.

Conwy Valley Windows are experts in providing and installing plumbing supplies. Our team of experts has many years of experience in what they do, not only have we all been through stringent plumbing courses, but we have on the job experience and have increased the energy efficiency of the homes of many customers across North Wales and England. Please dont hesitate to get in contact if there is anything at all you feel we can help you with.

To find out much more about our services, or to have a chat about what we could do for you, simply give us a call on 01492 554 000 or just send us an email to

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