How to choose your plumbing fittings?

To get stuck in, copper pipe fittings are brazed and require specialized plumbers' tools to install; olive joints, on the other hand, allow you to connect copper pipes without having to do any welding – brilliant! Screw fittings incorporate teflon or hemp fibre as a seal; specific PEX fittings are needed for a PEX installation and PVC fittings, for pressure or wastewater pipes, are glued. 90% of plumbing installations nowadays use copper pipes, so depending on how you rate your skills you'll need to use olive fittings, screw fittings and PVC fittings – typical for the wastewater side.

Welded fittings

Copper fitting

Copper fittings are connected to copper pipes via welding or brazing – a specialized welding technique which can either be 'strong' (hot water and heating pipes) or 'cold' (cold water pipes). Brazing is done with a blowtorch or flame welder and a filling metal chosen to suit the welded material. The fittings are sized to match the pipe and come in a variety of forms to suit your needs (elbow, T-joint, sleeve, etc.).

Making connections without welding

Screw fittings

Screw fittings are of course connected via a screw thread, with a seal formed of teflon or oakum (hemp fibre). Often used in domestic plumbing applications, they are made of brass or galvanized metal and are available with different types of screw thread with sizes expressed in mm or inches. Screw fittings can be male, female or male-female and come in the form of elbows, T-joints, sleeves and bungs and sometimes require washers.

Bicone or 'olive' fittings

A bicone fitting also allows two copper pipes to be connected without welding and is the quickest, easiest solution. Their working principle: a ring deformed by the screwing action forms a seal between the fitting and the pipe. Perfect if you don't have a welder or blowtorch.

PEX fittings

PEX is an abbreviation for cross-linked polyethylene, with specialized fittings for building plumbing installations. It makes a flexible pipe useful in renovation as well as new-build water and heating installations and, again, not requiring welding. There are four main types of PEX fittings: compression fittings, push fittings, sliding fittings and automatic fittings.

Compression fitting

As the name suggests, a seal is formed by compressing the pipe around the fitting. This is achieved with a nut, so all you need in terms of tools is a flat spanner of the right gauge.

Push fitting 

A little more complex than the compression type, here a seal is formed by forcing the fitting onto the end of the pipe. This may require the use of a pair of crimping pliers.

Sliding fitting 

This is the most reliable type of PEX fitting. It is used in heating applications, among other uses, where the seal must be perfect and durable. Fairly complex to assemble, you'll need some knowhow and the relevant equipment – flaring pliers and a specialized PEX crimping tool.

Automatic fitting

Similar to a compression fitting, the automatic type requires no prior knowledge or specialized equipment to assemble. The seal is formed by a clip activated by turning a nut. Easy to use, but unfortunately the least hardwearing of the PEX fitting options.

Adhesive fittings

PVC wastewater pipe fitting

Wastewater PVC isn't designed to support significant internal pressure; so the water is discharged under gravity. This type of PVC is commonly found in sink and washbasin outflow pipes, showers, baths and toilets.

When constructing an evacuation network, there are various types of PVC fitting at your disposal: elbows, T-joints, sleeves, reducers etc. in a range of diameters. These fittings are assembled with adhesive (specialized PVC glue), ensuring a robust and watertight seal.

PVC pressure fitting

Unlike wastewater PVC, pressure PVC (as the name suggests) supports a certain level of internal pressure; so it can be used on the supply side.

When constructing a pressure PVC network, there are also several different types of fitting to choose from (elbows, sleeves, Ts, reducers, scew fittings, ball valves, one-way valves, etc.).

These fittings are assembled either with adhesive (in the case of a M/F joint) or screwing where some kind of valve or a union joint is involved.

Types of fitting

Elbow

You can get elbow joints in various angles, but the most common are 27, 45 and 90°. These are flared to allow copper pipes to be inserted and welded in place. For ease of assembly, copper elbow joints are mainly used in renovation and repair work; in new-build settings it's easier and more reliable to bend the copper pipe itself – using annealed copper, it can be wrought into the desired elbow shape with a roll bender. Elbows maintain the same pipe diameter.

T-joint

A T-joint is a fitting in the shape of a 'T' which allows three pipes or other components to be fitted together. This can either connect three elements of the same diameter or incorporate a reduction.

Screw fitting with beaten collar

This type of fitting lets you attach a rigid copper pipe to another element or screw fitting. The term «beaten collar» refers to the end of a rigid pipe onto which the screw fitting is connected – requiring a joint which is located on the flat part created by the collar.

Sizes and uses

Material: brass or galvanized steel?

Galvanized steel offers an impressive level of resistance to oxidation, superior mechanical resistance to abrasion and better shear-resistance and tensile strength. It's not recommended in close proximity to non-galvanized steel elements or in damp areas due to the galvanic corrosion that can occur. It can be used both in drinking water and heating circuits (≤ 60°C); brass is more malleable and offers high corrosion-resistance in damp settings.

Types of fitting

Elbow

An elbow allows you to change the direction of a pipe by a set angle: 27°, 45° or 90°. Like a sleeve fitting, they can be male, female or male/female and can incorporate a diameter reduction.

Reducer

A reducer is a straight fitting that lets you connect two pipes of differing diameters, male or female: M20/27-F15/21; F12/17-M15/21, etc. The two diameters can only differ by one or two sizes.

Bung

A bung lets you end a pipeline or block off a component. It can be male or female, depending on the component it's attached to.

A bicone fitting is a copper fitting that doesn't require welding. A seal is formed by turning a nut, which deforms the pipe inside the fitting. The main advantage is its ease of use: it can be installed with a simple flat spanner and doesn't require any specialist knowledge; you just need the right diameter for your pipe and you can go straight ahead.This type of fitting doesn't require welding, adhesive or teflon (or indeed, oakum) and is specific to rigid copper pipes (not the annealed type). These fittings can only be used once: If you unscrew them again once installed, they lose their seal and you'll have to change the ring – which can be tedious.

Sizes and uses of bicone fittings

PEX installations 

As we saw above, PEX is a plastic used to make plumbing circuits, both for water supply and heating, and it can be more or less flexible.

Anyone can work with PEX with no specialist knowledge or particular flair for plumbing. There's no need for welding, and not much equipment is required.

Types of PEX fitting

Sliding fitting

This type is principally used in heating installations, since it's highly reliable in terms of robustness and minimizing leaks. The sliding fitting  does require a little bit of technique to assemble, as well as a few bits of equipment – flaring and crimping pliers.

Push fitting

Push fittings allow for very thorough assembly of PEX components. The fitting actually deforms under the action of crimping pliers and becomes an integral part of the installation.

Automatic fitting

This is the easiest type to assemble, but also the least reliable! Looks very similar to a compression fitting apart from the fact that the connection is achieved via a special clip mechanism. This is also controlled by a nut.

PEX fitting characteristics

There is an alternative to metallic fittings for assembling HDPE pipes (high-density polyethylene): polyethylene compression fittings.They work just like other compression fittings, but the seal is obtained by screwing. Generally they're only used in larger diameters (from 16mm up to 90mm). They're often found in water mains supplies for large buildings.

Diameter and uses

PVC pipes: wastewater vs pressure

Basic PVC as used in wastewater evacuation is a plastic material which doesn't hold up under pressure. Flow in a PVC wastewater network must therefore occur under gravity. It can be used for any domestic wastewater evacuation (sinks, washbasins, showers, baths, rainwater, etc.). It is recognizable by its light grey colour.

Pressure PVC has to be highly resistant, and is therefore much thicker than the previous type. As a result it can be used for water supply pipes (i.e. necessarily pressurized). It can be use to supply drinking water, water for pumping, etc. It is recognizable by its darker grey colour.

The whole of your household water evacuation network (kitchen, bathroom, etc.), sewage (i.e. toilet outflows) and rainwater piping can be made of PVC - with a few caveats.

The vast majority of this network will be assembled using adhesive fittings as described above. A minimum gradient needs to be incorporated so that evacuation flows smoothly and to prevent solid waste from causing blockages. All the wastewater pipes are combined into a storage tank before leaving your household water system (i.e. a septic tank), or are pumped directly into the public sewer system.

Rainwater can be distributed, captured, stored or evacuated via a network, an underground tank or an above-ground collector.

Diameters and uses

To find out more about DIY topics, follow our editors' advice and check out their other guides:

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