Choosing the Right Fittings & Valves for Your System

Fittings and valves are the two essential component groups that connect, direct, and control water and gas flow throughout any plumbing system. Fittings are the physical connectors used to join lengths of pipe together, change direction, reduce bore size, or branch a pipe run in a different direction — examples include elbows, tees, couplers, and reducers. Valves are the control components that allow water or gas flow to be started, stopped, regulated, or diverted at any point in the system. Together, fittings and valves form the structural framework of a plumbing installation, from the incoming mains supply right through to individual appliances and outlets. Choosing the correct fitting type and valve for each part of the system is critical for long-term reliability, compliance with Water Regulations, and ease of maintenance. You can browse the full range of plumbing fittings and plumbing valves available at MP Moran for your next project.

A fitting is a passive connector — it joins, redirects, or transitions pipe without any moving parts or control function. A valve is an active component that contains a moving mechanism, such as a ball, gate, or disc, which allows you to open, close, or regulate flow through the pipe. Fittings are permanent or semi-permanent parts of the pipework; valves are operational components that are used regularly during the life of the installation. For example, a compression elbow is a fitting that changes the direction of the pipe run, whereas a gate valve on the same run allows you to isolate a section for maintenance or repair. Both components must be rated for the correct pressure and temperature of the system they are installed in. In practice, most plumbing installations require both fittings and valves working together to create a safe, controllable system.

The four most common types of plumbing fittings used in UK residential and commercial installations are compression fittings, push-fit fittings, solder (end feed and solder ring) fittings, and press-fit fittings. Compression fittings use a nut and olive to grip the pipe mechanically and are widely used for copper and plastic pipe in accessible locations. Push-fit fittings use an internal grab ring and O-ring seal and require no tools to install, making them popular for fast repairs and new builds alike. Solder fittings are permanent copper connections made by heating the fitting and flowing solder to create a capillary joint, and are the traditional choice for concealed pipework. Press-fit fittings use a crimping tool to deform a sleeve around the pipe, creating a permanent, tool-formed connection that is increasingly common in commercial and new-build projects. You can explore compression fittings and press-fit fittings in the MP Moran range.

The three types of valves most commonly specified by plumbers in the UK are ball valves, gate valves, and check (non-return) valves. Ball valves use a rotating ball with a bore through the centre, operated by a quarter-turn handle, and provide fast, reliable shut-off with minimal flow restriction — they are the preferred isolating valve in most modern installations. Gate valves use a threaded spindle that raises or lowers a wedge-shaped gate to open or close the pipe, and are often found in older systems and on low-pressure cold water feeds. Check valves, also called non-return valves, allow flow in one direction only and prevent backflow contamination — they are required under Water Regulations wherever there is a risk of back-siphonage. Thermostatic radiator valves and motorised zone valves are also widely used in heating systems for temperature and flow control. Choosing the right valve type for the application, pressure rating, and position in the system is essential for safe and compliant installation. Browse plumbing valves and compression fittings at MP Moran for a full selection.

Push-fit fittings have a mixed reputation among professional plumbers, though most acknowledge they are excellent in the right situation. The main criticism is that they are less forgiving of pipe preparation — if the pipe end is cut slightly out of square, is scratched, or is not fully inserted to the depth mark, the O-ring seal can fail over time. Some plumbers are concerned about long-term reliability in concealed locations, particularly in walls or under floors where accessing a leak is costly and disruptive. Push-fit fittings are also not suitable for use on microbore pipe without inserts, and certain types are not approved for gas installations. That said, most experienced plumbers use push-fit fittings regularly for accessible locations, repairs, and new-build installations where the pipe is properly prepared. The key is using the correct fitting for the pipe material and diameter, and always inserting the pipe to the full depth. Browse the full range of push-fit fittings and compression fittings available at MP Moran.

Push-fit fittings do not leak when installed correctly, but they are more sensitive to installation quality than compression or soldered fittings. The most common cause of push-fit leaks is incomplete pipe insertion — the pipe must be pushed fully to the depth mark stamped on the fitting body for the internal grab ring and O-ring to seat properly. Pipe that is oval, scratched along the sealing zone, or has a burred cut edge can also prevent a reliable seal. Using a pipe insert (also called a liner or support sleeve) inside plastic pipe before fitting is essential to maintain the pipe bore under the grab ring and prevent the fitting from cutting into the pipe over time. Plastic push-fit fittings can also be affected by thermal expansion in hot water systems if the pipe is allowed to move excessively at the joint. Choosing a quality branded fitting rated for the correct temperature and pressure, and taking care with pipe preparation, will give a long-term leak-free joint. You can find a wide selection of push-fit fittings and press-fit alternatives in the MP Moran range.

No, 15mm and half inch (1/2 inch) are not the same size, though the two measurements are frequently confused because both are used for the same type of pipework in domestic plumbing. The confusion arises because 15mm refers to the outside diameter of modern metric copper or plastic pipe, while 1/2 inch is the nominal bore size used for older imperial pipe and for BSP (British Standard Pipe) threaded fittings. A 15mm compression fitting will not fit a 1/2 inch imperial copper pipe, and vice versa. BSP threads are measured by the nominal bore of the pipe they are designed for, so a 1/2 inch BSP thread has an actual outside diameter of approximately 20.9mm. In practice, most modern plumbing fittings in the UK are metric, and the 15mm compression or push-fit fitting is the standard for domestic hot and cold supply. When connecting to taps, valves, or appliances with threaded inlets, you will need a fitting that converts from 15mm pipe to the correct BSP thread size. Browse compression fittings and iron and brass fittings at MP Moran for the correct connectors.

No, 3/4 inch and 22mm are not the same size. The 22mm measurement refers to the outside diameter of metric copper or plastic pipe, while 3/4 inch refers to the nominal bore of imperial pipe or the thread size of BSP fittings and valves. A 3/4 inch BSP threaded connection has an actual outside thread diameter of approximately 26.4mm, which is significantly larger than 22mm pipe. Where you need to connect a 22mm pipe run to a 3/4 inch BSP threaded appliance or valve, you will need a 22mm to 3/4 inch BSP adaptor or connector fitting. In central heating systems, 22mm pipe is the standard main circuit pipe size in the UK, and connections to boilers, pumps, and manifolds frequently involve BSP threaded unions or adaptors. Always confirm thread size before purchasing valves or appliance connections to avoid wasted materials on site. Browse iron and brass fittings and plumbing valves at MP Moran for the correct connectors.

The four principal types of control valves in plumbing and heating systems are isolating valves, regulating valves, pressure relief valves, and check (non-return) valves. Isolating valves, such as ball valves and gate valves, are used to shut off the flow completely for maintenance, repair, or appliance replacement. Regulating valves, including thermostatic radiator valves, pressure reducing valves, and flow control valves, are used to set and maintain a desired flow rate or pressure within a circuit. Pressure relief valves are safety devices that open automatically when system pressure exceeds a safe threshold, protecting boilers, cylinders, and sealed systems from damage. Check valves allow flow in one direction only and prevent backflow, which is a Water Regulations requirement wherever contamination of the mains supply could occur. Motorised zone valves are a fifth common type used specifically in zoned central heating systems to control flow to individual circuits or cylinders under the direction of a programmer or thermostat. Browse the full range of plumbing valves and plumbing fittings at MP Moran.

Plumber's putty contains oils and compounds that can swell, crack, and degrade certain types of plastic, particularly ABS and some PVC formulations used in modern waste and supply fittings. Over time, this chemical incompatibility causes the fitting to weaken, potentially resulting in leaks or joint failure at a point that may be difficult to access. Plumber's putty is also not a reliable sealant for plastic-to-metal joints because it does not adhere to plastic surfaces in the same way it does to traditional ceramic or cast iron. For plastic waste fittings, the correct sealing method is the use of the rubber washers and seals supplied with the fitting, which compress to form a watertight joint when tightened correctly. Where a sealant is required on plastic supply fittings, PTFE tape on threaded connections or an approved jointing compound rated for plastic is the correct choice. Always check the manufacturer's installation instructions for the specific fitting type you are using to confirm the correct sealing method. Browse waste and trap fittings and push-fit fittings in the MP Moran range.

Experienced plumbers often prefer rigid copper pipework over flexible connectors in permanent installations because flexible connectors have a finite service life and can deteriorate without visible warning. Most corrugated stainless steel or braided flexible connectors are rated for a service life of around five to ten years, after which the corrugations or braid can fatigue and split, particularly in hot water applications. When a flexible connector fails behind an appliance such as a washing machine, dishwasher, or boiler, the resulting leak can cause significant water damage before it is detected. Flexible connectors also introduce additional joints into the system, and each joint is a potential failure point. That said, flexible connectors are a legitimate and often essential solution in tight spaces, when connecting to appliances that vibrate, or when the pipework alignment does not allow a rigid connection. The key is using a quality connector rated for the application and replacing it on a regular schedule rather than waiting for failure. Browse compression fittings and plumbing valves for rigid pipework solutions at MP Moran.

There are several pipe materials that are no longer recommended for new installations or that should be replaced as a priority if found in older properties. Lead pipe was used extensively in UK homes built before 1970 and should always be replaced, as lead can leach into drinking water and poses serious health risks — if you have a lead supply pipe, contact your water company about a replacement scheme. Grey polybutylene pipe (often marketed under brand names such as Acorn or JG Speedfit grey), which was commonly used in the 1980s and 1990s, has been found to become brittle with age and degrade in contact with chlorinated water, leading to failures and leaks within the pipe body rather than at fittings. Black iron or galvanised steel pipe found in older properties is prone to internal corrosion and scale build-up over time, restricting flow and eventually failing. Asbestos cement pipe, while now very rare, should only be removed by a licensed contractor. Modern copper, CPVC, and barrier pipe systems installed with quality compression or press-fit fittings are the recommended solution for long-lasting, safe plumbing installations.

The fittings used most frequently by plumbers in everyday work are compression fittings, push-fit fittings, and end feed or solder ring fittings for copper pipe work. Compression fittings are the most versatile general-purpose option — they work with both copper and plastic pipe, require no tools beyond a spanner, and can be dismantled if needed, making them ideal for accessible locations and service valves. Push-fit fittings are favoured for speed on new-build and renovation work, particularly where large volumes of plastic pipe are being installed quickly. Solder ring and end feed capillary fittings remain the choice for concealed copper pipework due to their slim profile and neat finish once soldered. Iron and brass fittings are used when connecting to threaded appliances, gas pipework, or older imperial systems where BSP threads are required. For plastic waste systems, solvent weld and push-fit waste fittings are the daily staples. You can find all of these fitting types in the MP Moran range, including compression fittings and iron and brass fittings.

The most common causes of plumbing fitting failures are incorrect installation, the wrong fitting type for the application, over-tightening, and deterioration of seals over time. Compression fittings are frequently over-tightened during installation, which can crack the olive, damage the pipe, or strip the thread — a fitting should be tightened by hand and then one to one-and-a-half turns with a spanner, not forced hard. Under-insertion of push-fit fittings is the leading cause of push-fit failures, as the pipe must reach the full depth mark for the seal to engage correctly. Using the wrong fitting material for the pipe type, such as using a copper olive in a plastic pipe compression fitting without a liner, will cause the fitting to cut into the pipe and leak over time. Fittings installed in systems running at pressures above their rated maximum will also fail prematurely. Thermal cycling on hot water systems can loosen joints over time if fittings are not adequately supported and the pipe is allowed to move. Specifying quality fittings rated correctly for the temperature, pressure, and pipe material of the system will prevent most failures. Browse the full plumbing fittings range and plumbing valves at MP Moran.

The 135 degree rule is a guideline used in waste pipe installation, particularly for connecting soil pipes and WC branch connections to the main soil stack. It states that branch connections into a soil stack should be made at an angle of 135 degrees rather than at 90 degrees, which in practice means using a swept 45 degree entry fitting rather than a sharp right-angle branch. This angled connection allows waste and soil to flow in the direction of travel in the stack without striking the opposite wall, which reduces the risk of blockages, cross-flow contamination between branches, and the induction of negative pressure that can siphon water seals from traps. A loss of the water seal in a trap allows sewer gases, including hydrogen sulphide and methane, to enter the building — which is both unpleasant and potentially dangerous. The 135 degree entry rule is referenced in BS EN 12056 and the Building Regulations Approved Document H, which govern below-ground and above-ground drainage design. Using the correct swept entry fittings from the outset avoids costly remedial work and ensures the system performs correctly over its lifetime. Browse waste traps and WC connectors and plumbing fittings at MP Moran.