John Guest connectors for filters, reverse osmosis, and water treatment at home: most commonly used sizes and fittings
Many customers come to Install Beer looking for John Guest connectors to repair, install or extend a water filter, an under-sink reverse osmosis system, an American fridge, a filtered water tap, a dispenser, a chiller or a domestic water treatment system. In this sector, the most common sizes are 1/4" OD tube and 3/8" OD tube, with adapters to NPTF, BSP and UNS threads depending on the equipment installed.
Quick summary
In domestic under-sink water filters and reverse osmosis, the most common size is usually 1/4" OD tubing, especially on outlets to the tap, pressurised tank, post-filter, restrictor, membrane and internal connections. In higher-flow units, main inlet, American fridges, dispensers or direct-flow systems, 3/8" OD tubing appears frequently. The most sought-after fittings are 1/4" straight union, 1/4" elbow, 1/4" tee, 1/4" valve, 3/8" to 1/4" adapter, 3/8" union, 3/8" elbow, 7/16"-24 UNS tap connector, NPTF adapters, bulkhead fittings, clips, plugs and LLDPE tubing.
The key idea: in osmosis and filters, tube is measured on the outside
On John Guest push‑fit fittings, the size is taken from the outer diameter of the tube. A tube with 1/4" outer diameter is not the same as 6 mm; a tube with 3/8" outer diameter is not the same as 10 mm; and a 1/2" BSP thread is not a 1/2" tube. Before buying, you must confirm whether the size refers to the tube, a thread or a hose.
This article complements the John Guest range and AquaTaps solutions
This guide helps identify sizes, fittings and adapters used in water filters, reverse osmosis and domestic treatment. To buy specific parts, check stock or search for connectors by format, see the John Guest fittings collection and the connectors and fittings category. If you’re looking for a complete filtered, chilled or sparkling water solution for home, office or hospitality, also check out AquaTaps and the water dispensers collection.
Guide contents
- What is used in domestic filters and reverse osmosis
- Most common sizes
- Why the 1/4" tube dominates
- When 3/8" tube appears
- 6 mm, 8 mm, 10 mm and metric sizes
- NPTF, BSP and UNS: common threads
- Which John Guest range to use
- List of the most common connectors
- Which fitting to use depending on the area of the equipment
- Connection to reverse osmosis tap
- American fridges and ice machines
- How to install push-fit fittings
- Recommended spare parts kit
- Common mistakes
- What to buy at Install Beer
- Frequently asked questions
What is used in filters, reverse osmosis and domestic water treatment
Domestic water treatment systems are usually installed under the sink, next to the cold-water supply, near an auxiliary tap, a fridge or a small dispenser. In these tight spaces, push-fit connectors are very useful because they allow assembly and disassembly without soldering, gluing, threading pipes or using special tools.
In reverse osmosis and under‑sink filters, circuits are usually divided into several zones: water inlet, pre‑filters, membrane, tank, post‑filter, filtered water tap, drain and, in some cases, connection to an American fridge or dispenser. Each point may use a different fitting.
Dominant size in domestic reverse osmosis, filtered taps, post-filters, tanks and internal branches.
Common at water inlet, higher-flow units, fridges, dispensers, and direct-flow systems.
Common threads in adapters, reverse osmosis taps, filter housings, valves and imported equipment.
Most common sizes in domestic water treatment
The following table summarizes the sizes that appear most frequently in filters, reverse osmosis systems, American refrigerators, dispensers and small water appliances in the home. The recommendation is always to measure the outside of the tube and confirm whether the part you want to connect is tube or thread.
| Size | Where it appears | Usual use | What to order |
|---|---|---|---|
| 1/4" OD | Under-sink reverse osmosis, auxiliary tap, tank, membrane, post-filter, restrictor and internal connections. | Thin line for filtered water or permeate. | John Guest fittings for 1/4" OD tubing. |
| 3/8" OD | Water inlet, higher-flow filters, American fridges, dispensers and direct-flow systems. | Supply with higher flow or outlet to equipment. | John Guest fittings for 3/8" OD tubing. |
| 1/2" OD | High-flow units, light commercial applications, or imported systems. | Sections of larger diameter in water or dispensing. | 1/2" OD fittings, not to be confused with 1/2" thread. |
| 6 mm | Some European equipment, compact filters or OEM components. | Fine metric line. | 6 mm metric fitting, not 1/4". |
| 8 mm | European equipment, coffee machines, filters, water and dispensing. | Water branches or auxiliary equipment. | 8 mm metric fitting, not 5/16". |
| 10 mm | Higher-flow filters, water equipment or transition from plumbing. | Inlet or outlet with higher flow rate. | 10 mm fittings or adapters to 3/8" if the system requires it. |
| 3/8" BSP | Under‑sink connections, braided hoses, angle valves and European accessories. | Adapt the domestic mains to filter or osmosis tubing. | BSP adapter to 1/4" or 3/8" tube depending on the unit. |
| 1/2" BSP | Taps, water outlets, filter housings, valves and domestic accessories. | More robust European hydraulic connection. | 1/2" BSP adapter to push-fit tube. |
| 3/4" BSP | Appliance connections, washing machine/dishwasher taps and some inlets. | Equipment supply or auxiliary connection. | 3/4" BSP adapter to 1/4" or 3/8" tube if applicable. |
| 7/16"-24 UNS | Reverse osmosis and filtered water taps, especially in the international market. | Connect 1/4" or 3/8" tubing to the filtered water tap. | Tap connector 1/4" or 3/8" x 7/16"-24 UNS. |
| 1/4" NPTF / 3/8" NPTF | Filter housings, imported equipment, valves, heads and US accessories. | Adapt push-fit tube to American thread. | Male or female NPTF adapter depending on the part. |
Do not confuse 1/4" with 6 mm or 3/8" with 10 mm
1/4" is approximately equivalent to 6.35 mm and 3/8" to 9.52 mm. Although they may visually appear close to 6 mm or 10 mm, in push-fit fittings this difference can cause leaks, poor insertion, or disconnection. If the tube is imperial, use an imperial fitting; if it is metric, use a metric fitting.
Why 1/4" tubing dominates in domestic reverse osmosis
1/4" OD tubing is very common because the flow rates of a traditional reverse osmosis system are low and because many of the unit’s internal connections use small lines: feed to prefilter, membrane outlet, postfilter, tank, auxiliary tap, flow restrictor and drain connections.
- Outlet of osmotised water to tap.
- Connection to pressurized tank.
- Carbon post-filter.
- Membrane and flow restrictor connections.
- Compact under-sink units.
- Connection to small dispensers.
- 1/4" straight union.
- 1/4" elbow.
- 1/4" T.
- 1/4" shut-off valve.
- 7/16"-24 UNS tap connector.
- 1/4" x 1/4" NPTF adapter.
- 1/4" plug.
When 3/8" tube appears in filters and water treatment
3/8" OD tubing usually appears when higher flow or lower pressure drop is needed: main system inlet, outlet to dispenser, American fridge, direct-flow unit, higher-capacity filter, water chiller or semi-professional installation.
| Use of 3/8" | Why it is used | Common fittings |
|---|---|---|
| Water inlet to the equipment | Allows a higher flow rate than 1/4" in certain systems. | 3/8" x NPTF/BSP adapter, 3/8" valve, 3/8" union. |
| American fridge | Some connections to refrigerator or ice maker use 1/4" and others 3/8" depending on the equipment. | 3/8" to 1/4" reducer, union, shut‑off valve. |
| Direct flow osmosis | It may require more flow than a tank‑based reverse osmosis system. | 3/8" straight connector, 3/8" elbow, 3/8" tee, reducer to 1/4". |
| High‑flow under‑sink filter | Better water flow and less restriction. | 3/8" to threaded adapters, 3/8" shut-off valve. |
| Water dispenser or chiller | It can supply a piece of equipment with higher demand. | 3/8" straight connector, valve, tee, threaded adapter. |
6 mm, 8 mm, 10 mm and metric sizes in European equipment
Although the under-sink osmosis and filtration market works largely with imperial sizes, metric sizes also appear, especially in European equipment, coffee machines, water systems, dosing, small vending, dispensers or mixed installations.
| Metric size | Close equivalent | Risk of confusion | Tip |
|---|---|---|---|
| 6 mm | Close to 1/4" but not the same. | 1/4" tubing measures 6.35 mm. | Do not swap them without confirming tolerance and fitting. |
| 8 mm | Close to 5/16". | 5/16" measures 7.94 mm. | In some cases it appears compatible, but this must not be assumed. |
| 10 mm | Close to 3/8" but not the same. | 3/8" measures 9.52 mm. | A 3/8" fitting is not a 10 mm fitting. |
| 12 mm | Close to 1/2" but not the same. | 1/2" OD measures 12.7 mm. | Measuring before buying is very important. |
NPTF, BSP, and UNS: common threads in filters and osmosis
In domestic water treatment, European, American and tap-specific threads for filtered water are mixed together. This is one of the most frequent causes of error when buying connectors.
| Thread | Where it appears | Usual use | Warning |
|---|---|---|---|
| 1/4" NPTF | Filter housings, heads, valves and imported equipment. | Male or female adapter to 1/4" or 3/8" tube. | Do not confuse with BSP. |
| 3/8" NPTF | Higher-flow equipment or imported accessories. | Adaptation to 3/8" or 1/2" tube. | American thread; identify before assembly. |
| 3/8" BSP | Angle valves, braided hoses, taps, and European domestic outlets. | Connection to mains under the sink. | Confirm male/female and type of seal. |
| 1/2" BSP | Taps, outlets, filter housings and plumbing accessories. | Adapt domestic mains to the filter system. | It is not 1/2" OD tube. |
| 3/4" BSP | Washing machine/dishwasher outlets, appliances and some inlets. | Supply from an appliance outlet. | May require a flat gasket and specific adapter. |
| 7/16"-24 UNS | Tap for reverse osmosis or filtered water. | Connect 1/4" or 3/8" tube to the auxiliary tap. | Very common in tap connector; it is neither BSP nor NPT. |
Which John Guest range to use for filters and reverse osmosis
Several John Guest ranges appear in water treatment. The choice depends on the liquid, pressure, temperature, cleaning chemical, compatibility with drinking water, and tube size.
| Range | Usual colour | Typical use | When it fits |
|---|---|---|---|
| PP White Polypropylene | White | Drinking water, filtration, reverse osmosis, water treatment and pure water. | It is one of the most common ranges for under-sink filters and reverse osmosis units. |
| PI Grey Acetal | Gray | Potable liquids, dispensing, beverages, food grade and auxiliary applications. | Widely used in beverage, water, equipment and spare parts in inch sizes. |
| PM Metric Acetal | Black | Metric sizes, water, beverages, inert gases and technical equipment. | Useful if the unit works with 6, 8, 10, or 12 mm tubing. |
| CI White Acetal | White | Water industry, potable liquids and intermittent hot water depending on the product. | May appear in tap connectors, BSPP and water applications. |
| Accessories | Various | Clips, plugs, inserts, collet covers, tube cutters and brackets. | Essential for a clean installation and maintenance. |
Not all fittings are suitable for everything
A fitting suitable for drinking water or filtration must not automatically be used for gas, fuel, compressed air, vacuum, aggressive chemicals, continuous hot water, or critical installations. In water treatment, always confirm range, pressure, temperature, chemical compatibility, thread, and tube type.
List of the most common John Guest connectors for filters, reverse osmosis and domestic water
The following table compiles the most common parts for repairing or assembling filtration systems, reverse osmosis, filtered water taps, American refrigerators, and domestic dispensers. References may vary by market, range, color, suffix, or availability, so they should be used as technical guidance.
| Connector or accessory | Common size | Indicative references | Typical use | Priority |
|---|---|---|---|---|
| Straight equal union | 1/4" x 1/4" | PP0408W / PI0408S | Repair or join 1/4" tubing in reverse osmosis systems and filters. | Very high |
| Equal 90° elbow | 1/4" x 1/4" | PP0308W / PI0308S | Run lines under the sink or inside the unit. | Very high |
| Equal T | 1/4" x 1/4" x 1/4" | PP0208W / PI0208S | Create branches in the filtered water line. | High |
| Shut-off valve | 1/4" | ASV9 / ASV10 / depending on range | Shut off inlet, tank or tap outlet. | Very high |
| Plug / end cap | 1/4" | PP4608W / PM0808R depending on the range | Temporarily cap a branch or outlet. | High |
| Male NPTF adapter | 1/4" tube x 1/4" NPTF | PP010822W / PI010822S | Connect 1/4" tube to a filter housing or head with female thread. | Very high |
| Male NPTF adapter | 1/4" tube x 1/8" NPTF | PP010821W / PI010821S | Small equipment, valves, and imported accessories. | Medium‑high |
| Female NPTF adapter | 1/4" tube x 1/4" NPTF female | PP450822W | Connect to a part with 1/4" NPTF male thread. | Medium‑high |
| UNS tap connector | 1/4" tube x 7/16"-24 UNS | PP3208U7W | Connect 1/4" tubing to the tap for reverse osmosis or filtered water. | Very high |
| Straight equal union | 3/8" x 3/8" | PP0412W / PI0412S | Repair, extend or join higher-flow lines. | Very high |
| Equal 90° elbow | 3/8" x 3/8" | PP0312W / PI0312S | Turns at inlet, filter outlet, fridge or dispenser. | High |
| Equal T | 3/8" x 3/8" x 3/8" | PP0212W / PI0212S | Branch off to a filter, tap, dispenser or fridge. | High |
| Shut-off valve | 3/8" | ASV7 / ASV8 / depending on range | Shut off supply to filter, fridge, dispenser, or unit. | Very high |
| Straight reducer | 3/8" x 1/4" | PP201208W / PI201208S | Go from 3/8" inlet to 1/4" internal circuit. | Very high |
| Reducing elbow | 3/8" x 1/4" | PP211208W / PI211208S | Reduce and turn in compact under-sink spaces. | High |
| Push-in elbow | 3/8" stem x 1/4" tube | PP221208W | Create an angled outlet by inserting one end into another fitting. | Medium‑high |
| Push-in elbow | 3/8" stem x 3/8" tube | PP221212W | Modular elbow for equipment and 3/8" lines. | Medium |
| UNS tap connector | 3/8" tube x 7/16"-24 UNS | PP3212U7W | Connect 3/8" tube to a compatible filtered water tap. | High |
| Bulkhead / bulkhead fitting | 1/4" or 3/8" | PP1208W / PP1212W | Pass through panels, auxiliary countertops or equipment housings. | Medium |
| 2‑way splitter | 3/8" | PP2312W | Split one line into two water outlets. | Medium‑high |
| 3-way divider | 1/4" and 3/8" combinations | PP30080812W / PP30120812W / PP30121208W | Compact distribution in filtration or dispensing systems. | Medium |
| Tube-to-hose connector | 3/8" to barb/hose | PP251208W / PI251208S and variants | Connect rigid tube to flexible hose if the equipment requires it. | Medium |
| Safety clip | 1/4" / 3/8" / 1/2" | PIC1808R / PIC1812R / PIC1816R | Help prevent accidental disconnections. | High |
| LLDPE tubing | 1/4", 3/8", 1/2" and metric | Depending on colour and coil | Replace lines, expand the unit or repair leaks. | Very high |
| Tube cutter | Up to 12 mm / 22 mm depending on model | JG-TS / TSNIP | Make a straight cut and avoid leaks. | Essential |
Looking for a specific John Guest size for a filter or reverse osmosis system?
At Install Beer we are official John Guest distributors in Spain and can help you identify the correct fitting if you have a photo, the outside diameter of the tube and the type of thread or equipment you want to connect.
See John Guest connectors Check compatibilityWhich fitting to use depending on the area of the equipment
A domestic reverse osmosis or filtration system does not have a single connection. It may include mains inlet, valve, pre-filters, membrane, tank, post-filter, tap, drain, fridge and dispenser. Each area tends to use a specific type of fitting.
| System area | Common connectors | Common sizes | Practical tip |
|---|---|---|---|
| Cold water inlet | BSP/NPTF adapter, shut-off valve, take-off tee, and reducer. | 3/8" BSP, 1/2" BSP, 3/4" BSP, 1/4" OD, 3/8" OD. | Confirm the thread of the under-sink connection before buying. |
| Prefilters | NPTF adapters, elbows, unions, clips and tubing. | 1/4" and 3/8". | Do not overtighten plastic threads on filter housings. |
| RO membrane | Elbows, unions, restrictor, shut-off valve and plugs. | Mainly 1/4". | Respect inlet, permeate, reject and flow direction. |
| Pressurized tank | Tank valve, 1/4" union, elbow and T. | 1/4". | Check tank pressure and valve tightness. |
| Post-filter | Straight connector, elbow, adapters and tube. | 1/4" or 3/8" depending on the unit. | Avoid kinking the tube when closing the cabinet. |
| Filtered water tap | Tap connector UNS, threaded adapter or specific connection. | 1/4" x 7/16"-24 UNS or 3/8" x 7/16"-24 UNS. | Check the actual thread of the tap. |
| American fridge | Union, valve, 3/8" to 1/4" reducer, NPTF adapter. | 1/4" and 3/8". | Identify whether the fridge uses a 1/4", 3/8" or proprietary inlet thread. |
| Dispenser or cooler | Union, elbow, valve, LLDPE tubing, and adapters. | 3/8" is common; 1/4" is also used in small units. | Assess flow rate and inlet pressure. |
| Leak repair | Straight union, elbow, plug, tube cutter and length of tube. | The size of the line that is damaged. | Cut a new, straight section; do not reuse chewed-up tubing. |
Connection to reverse osmosis or filtered water tap
The auxiliary filtered water tap can be one of the most confusing points. Some taps use compression connections, others specific fittings and others 7/16"-24 UNS threads. That’s why it’s a good idea to identify the tap thread before buying the adapter.
- 1/4" tube x 7/16"-24 UNS.
- 3/8" tube x 7/16"-24 UNS.
- 1/4" compression tube.
- NPTF or BSP threaded adapter depending on the tap.
- Manufacturer’s proprietary connection.
- Measure the tube on the outside.
- Check the tap thread.
- Check whether it needs a flat gasket.
- Do not force plastic or metal threads.
- Perform a leak test before installing the cabinet.
American refrigerators, ice machines and dispensers
American fridges, ice makers and domestic dispensers usually use small-diameter lines. In many cases 1/4" OD appears, although some units or installations use 3/8" OD for the feed or specific adapters. Before connecting, check the manufacturer’s manual, inlet pressure, need for a filter and thread type.
Pay attention to pressure and to the unit’s warranty
In fridges and ice machines, an incorrect connection can cause leaks, damage to the unit or loss of warranty. Identify the actual tube size, use fittings suitable for drinking water and do not connect at pressures outside the rated range.
How to correctly install a John Guest push-fit fitting
Most leaks in push-fit fittings are not due to the fitting itself, but to a bad cut, oval tube, tube not fully inserted, burrs, lateral stress, forced thread, incorrect seal, or wrong size.
1. Shut off the water
Close the shut-off valve and release pressure before dismantling any connection.
2. Measure the pipe on the outside
Use a caliper if possible. Distinguish 1/4", 3/8", 6 mm, 8 mm, and 10 mm.
3. Cut square
Use a tube cutter. A crooked cut can damage the O-ring and cause leaks.
4. Remove burrs
The tube must be clean, with no deep scratches, crushing or deformation.
5. Push in all the way
Push the tube straight all the way into the fitting. Do not leave it halfway in.
6. Strip for verification
Check that the clip has gripped the tube and that it does not come loose.
7. Fit clip if applicable
In areas with movement or difficult access, a clip helps prevent accidental disconnections.
8. Turn on the water and check
Perform a pressure leak test before closing the cabinet or leaving the unit running.
Useful photo to identify the fitting
To choose correctly, prepare a clear photo of the old fitting, a photo of the unit where it is connected, the outer measurement of the tube with calipers and, if there is a thread, a photo of the thread or the unit manual. This helps avoid confusing 1/4", 3/8", 6 mm, 10 mm, BSP, NPTF or UNS.
Recommended John Guest spare parts kit for filters and reverse osmosis
A small selection of fittings can solve many domestic issues: leak from cut tubing, filter change, new tap, fridge connection, valve replacement, or adaptation between 3/8" and 1/4".
| Item | Recommended quantity | Function |
|---|---|---|
| 1/4" straight union | 2 units | Repair or extend reverse osmosis lines. |
| 1/4" elbow | 2 units | Resolve bends under the sink. |
| T 1/4" | 1 unit | Create an auxiliary branch. |
| 1/4" shut-off valve | 1–2 units | Isolate tank, tap or unit line. |
| 3/8" straight connector | 1–2 units | Repair inlet or outlet of higher flow. |
| 3/8" to 1/4" reducer | 2 units | Adapt unit inlet or outlet. |
| Male NPTF adapter | Depending on the equipment | Connect to filter housings, heads or valves. |
| 7/16"-24 UNS tap connector | 1 unit if your tap requires it | Connect tubing to the filtered water tap. |
| 1/4" and 3/8" plug | 1 unit of each | Temporarily cap a line. |
| Safety clips | Various | Avoid accidental disconnections. |
| LLDPE tube 1/4" and 3/8" | 1–2 metres or short coil | Replace damaged sections. |
| Tube cutter | 1 unit | Make straight cuts and prevent leaks. |
Common mistakes when buying John Guest connectors for filters and reverse osmosis
| Error | Consequence | How to avoid it |
|---|---|---|
| Confusing 1/4" with 6 mm | The tube does not fit well or may leak. | Measure the actual outside diameter. |
| Confusing 3/8" with 10 mm | Unsafe or incompatible connection. | Differentiate imperial and metric sizes. |
| Mixing up tube with thread | An incorrect adapter is purchased. | Confirm whether it is OD, BSP, NPTF or UNS. |
| Not knowing whether the thread is male or female | The adapter does not fit the equipment. | Check the part it has to screw into. |
| Mixing BSP with NPTF | Damaged thread or leak. | Identify the standard before tightening. |
| Reusing marked or deformed pipe | The O-ring may not seal. | Cut a new, straight section. |
| Do not use a tube cutter | Crooked cut, burrs and leaks. | Use a John Guest pipe cutter or suitable tool. |
| Over‑tightening plastic threads | Cracks or breakage of the filter housing. | Tighten appropriately and use a compatible gasket. |
| Do not check pressure | Leaks or damage to the unit. | Check the maximum pressure of the filter, fitting and tube. |
| Using fittings that are not suitable for drinking water | Health risk or incompatibility. | Use components suitable for drinking water and water treatment. |
What to buy at Install Beer for domestic filters, reverse osmosis and water treatment
Install Beer works with John Guest every day in real beverage, water, filtration, dispensing, and technical systems installations. For domestic filter and osmosis clients, the most useful selection is usually concentrated on 1/4", 3/8" fittings, threaded adapters, valves, reducers, LLDPE tube, and tube cutters.
| Need | Recommended product | Internal link |
|---|---|---|
| View the full John Guest range | Push-fit fittings, valves, adapters, pipes and accessories. | John Guest collection |
| Search fittings by type | Elbows, tees, unions, reducers, check valves and adapters. | Connectors and fittings |
| Replace filter or reverse osmosis tubing | Food-grade and LLDPE tubing compatible with water or beverages. | Food-grade tubing |
| Cut pipe correctly | John Guest pipe cutter for a clean, square cut. | John Guest tube cutter |
| Isolate a section | John Guest shut-off valve for maintenance or repair. | John Guest shut-off valve |
| Adapt to thread | Male, female or swivel elbow BSP/BSPT/NPTF adapters depending on the equipment. | Male BSPT thread adaptor |
| Connect to hose | John Guest pipe-to-hose adapter. | Pipe-to-hose adapter |
| Study a complete water solution | Filtered, chilled, ambient or sparkling water for home, office or HORECA. | AquaTaps solutions |
Not sure which connector you need for your filter or reverse osmosis system?
Send us a photo of the fitting, the outside diameter of the tube, and the equipment it connects to. We’ll help you distinguish 1/4", 3/8", 6 mm, 8 mm, 10 mm, NPTF, BSP, UNS, male, female, elbow, tee, valve, or adapter.
Buy John Guest Check the sizeFrequently asked questions about John Guest connectors for filters and reverse osmosis
Which tube size is most commonly used in domestic reverse osmosis?
The most common size is 1/4" outer diameter. In higher-flow units, water inlets, American fridges or direct-flow systems, 3/8" outer diameter also appears.
Are 1/4" and 6 mm the same?
No. 1/4" is approximately 6.35 mm. In push-fit fittings that difference can cause incompatibility or leaks. If the tube is 1/4", use a 1/4" fitting; if it is 6 mm, use a 6 mm fitting.
Are 3/8" and 10 mm the same?
No. 3/8" is approximately equivalent to 9.52 mm. Although it seems close to 10 mm, compatibility must not be assumed without checking the system.
Which John Guest connectors are most useful for osmosis?
The most common are 1/4" straight union, 1/4" elbow, 1/4" tee, 1/4" valve, 3/8" to 1/4" adapter, 7/16"-24 UNS tap connector, 3/8" union, 3/8" elbow, 3/8" valve, plugs, clips, and LLDPE tubing.
What is the 7/16"-24 UNS thread?
It is a common thread on some reverse osmosis or filtered water taps. It is used with tap connectors for 1/4" or 3/8" tubing, depending on the model.
Are BSP and NPTF compatible?
They must not be mixed without confirming compatibility. BSP is a common thread in Europe and NPTF is an American thread. Forcing them together can cause leaks or damage the part.
Can I use John Guest fittings with drinking water?
Yes, as long as you choose the right range for drinking water, filtration or water treatment and respect the pressure, temperature and compatibility conditions indicated by the manufacturer.
Do I need safety clips?
Not always, but they are recommended in areas where the tube may move, become tensioned, or be difficult to inspect. They help avoid accidental disconnections.
What tubing should I buy for a reverse osmosis system?
It depends on the unit. Most domestic reverse osmosis systems use 1/4" OD tube, but some units use 3/8" OD on inlet, outlet or higher-flow lines. Always measure the outside diameter of the existing tube.
Can Install Beer help me identify the fitting?
Yes. As official John Guest distributors in Spain, we can help you identify sizes and connectors if you send us photos, the tube’s outside diameter and details of the equipment it connects to.
Technical note: this guide focuses on drinking water systems, filtration, reverse osmosis and domestic water treatment compatible with push-fit fittings. It must not be used as instruction for gas, fuel, compressed air, heating, aggressive chemicals, critical circuits or non-compatible installations. Always confirm pressure, temperature, size, thread, regulations and product compatibility before installing.