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Choosing a Pipe Jointing Compound for Metal Threaded Connections

A pipe thread sealant fills the microscopic clearances and spiral leakage path that remain when male and female metal threads are tightened. It supports the mechanical joint but does not repair cracked fittings, restore incorrectly cut threads or compensate for an unsuitable thread combination. Reliable selection requires confirmation of the conveyed medium, maximum pressure, operating and transient temperatures, thread form, fitting material, pipe size, curing conditions and regulatory approval.

The two products in this category use different sealing mechanisms. White Pipe Jointing Compound remains non-hardening and pliable. Liquid PTFE is an anaerobic methacrylate resin that polymerises after it is confined between close-fitting metal surfaces and deprived of air. They must not be treated as interchangeable solely because both are applied to pipe threads.

Product Comparison

Property	VITCAS Pipe Jointing Compound	Liquid PTFE Anaerobic Thread Sealant
Product format	400g ready-to-use cream or beige paste	50ml ready-to-use light-blue gel
Sealing mechanism	Non-hardening compound that fills thread clearances and remains pliable	Anaerobic resin that cures when confined between close metal surfaces without air
Published temperature	Up to 200°C	Up to 150°C
Published pressure	Up to 7 bar	Instant low-pressure sealing is stated, but no numerical final pressure rating is published on the product page
Published media	Natural gas, LPG vapour, low-pressure steam and hot or cold water	Hot and cold water, gas and compressed air
Joint and substrate	Metal threaded pipe joints; listed as non-corrosive to aluminium, brass, copper, low-carbon steel and zinc	Close-fitting metal threaded joints, with gaps up to 0.3mm
Published standards	Product states conformity with BS EN 751-2:1997 and BS 6956-5:1992	Product refers to metal testing in accordance with ISO 10964; no BS EN 751-1 conformity is stated on the page
Dismantling	Non-hardening character assists adjustment and disassembly	Low cured mechanical strength is intended to permit disassembly with conventional hand tools

Non-Hardening Pipe Jointing Compound

The white compound is used as a pliable sealing paste on compatible screwed metal pipework. It fills local thread imperfections and also lubricates the joint during tightening, helping to reduce galling and seizure. Because it does not cure into a rigid polymer, the joint can generally be adjusted or dismantled more readily during maintenance.

The product page lists natural gas, LPG, low-pressure steam and water at hot or cold temperatures, together with maxima of 7 bar and 200°C. Do not assume that both maxima apply simultaneously to every medium. The permitted pressure-temperature envelope may be lower for a particular gas, water or steam service. Obtain the current technical data and verify the exact duty before specification.

Anaerobic Liquid PTFE Thread Sealant

Liquid PTFE is described as a single-component anaerobic sealant based on methacrylic resin. It remains liquid while exposed to air but cures when trapped between close metal threads. The product is listed for thread gaps up to 0.3mm and performs best during curing at approximately 20–25°C. Lower temperatures, passive metals and larger clearances may delay polymerisation.

The stated instant low-pressure seal is an initial sealing property; it is not evidence of full cure or permission to apply the final system pressure immediately. The installation must observe the documented fixture time, full-cure time and pressure-test schedule. These values are not currently displayed on the product page and should be obtained from the latest technical data sheet.

Despite the product name, liquid PTFE is not simply PTFE tape in liquid form. It is a curing anaerobic resin and requires two suitable metal surfaces, close thread engagement and appropriate curing conditions.

Suitable Connection Types

Both products are intended for threaded metal connections. Confirm that the male and female thread standards are mechanically compatible and capable of forming the designed joint. A sealant cannot make a mismatched parallel and taper thread combination acceptable, correct cross-threading or restore a fitting that has been over-tightened.

Do not use these compounds as a general substitute for:

• compression olives or ferrules;
• flat flange gaskets;
• O-rings and elastomeric seals;
• push-fit pipe connectors;
• solvent-welded or fusion-welded plastic pipe;
• soldered, brazed or press-fit connections;
• damaged fittings that require replacement.

If a fitting combines a threaded section with another sealing element, establish which surface is intended to create the seal. Applying compound to the wrong area may obstruct assembly or contaminate the system without improving leak tightness.

Metal and Plastic Compatibility

White Pipe Jointing Compound is listed as non-corrosive to aluminium, brass, copper, low-carbon steel and zinc. Liquid PTFE is specified for metal threads. The rate of anaerobic cure can vary between active metals, passive metals such as stainless steel, and plated or coated surfaces. Confirm whether an activator is required where cure speed is critical.

Do not apply either product to plastic threads unless the exact plastic, joint design and sealant have been approved together. Some thread sealants can stress-crack thermoplastics, and the lubricating effect can make it easier to over-tighten and split a plastic female fitting. A product intended for metal threads is not automatically compatible with PVC, CPVC, ABS, nylon, polypropylene or composite fittings.

Water and Heating Systems

The white compound is listed for hot and cold water and is associated with BS EN 751-2 and BS 6956-5. The scope of these standards includes particular metallic threaded joints used with heating water and, for BS 6956-5, specified water and low-pressure saturated-steam duties. This does not by itself establish approval for drinking water.

Where water is for human consumption, obtain current evidence of the required potable-water or regulatory approval for the exact product. The term “non-toxic” and general suitability for water do not replace WRAS acceptance or another approval required by the relevant authority, specification or jurisdiction.

On sealed central-heating circuits, check compatibility with corrosion inhibitors, glycol antifreeze, cleaning chemicals and other treatment products. A generic water claim is not a complete chemical-compatibility table.

Natural Gas and LPG

White Pipe Jointing Compound states conformity with BS EN 751-2:1997. This standard covers non-hardening compounds for metallic threaded joints in contact with first-, second- and third-family gases, with LPG covered in vapour rather than liquid form. The product also lists natural gas and LPG among its applications.

Gas work must be undertaken and tested by a person legally competent for the installation and gas type. In UK domestic premises this generally means a Gas Safe registered engineer with the appropriate category of competence. The engineer must confirm that the product, thread, pipe size and pressure fall within the applicable standard and installation rules.

The anaerobic product page mentions gas but does not state conformity with BS EN 751-1, the standard specifically covering anaerobic jointing compounds for specified gas and heating-water applications. Do not infer certification from the curing chemistry or from ISO 10964 testing. Obtain the required approval documentation before using it on regulated gas pipework.

Steam, Compressed Air and Industrial Fluids

Low-pressure steam is listed for the white compound, with published maxima of 7 bar and 200°C. Steam pressure and saturation temperature are linked, so the actual permitted condition must be checked rather than selecting pressure and temperature independently. Confirm whether the service is saturated steam, wet steam or superheated steam and follow the product's approved operating envelope.

Compressed air is listed for the anaerobic sealant. Verify pressure, temperature, compressor lubricant, condensate and required air quality. Neither product should be promoted for breathing air, medical gases or other high-purity gas service without explicit approval.

The current white-compound page makes broad references to crude oil, fuels, hydraulic fluids, refrigerants, solvents, chemical processing and power-generation systems. These uses require medium-specific compatibility and pressure-temperature data that are not published on the page. Do not assume suitability for them without written technical confirmation.

Oxygen and Other Oxidising Gases

Do not use either compound in oxygen-enriched service unless the exact product has documented oxygen compatibility for the required pressure and cleanliness standard. Oils, greases and many organic sealants can present a serious ignition hazard in oxygen systems. Medical oxygen, industrial oxygen and other oxidising gases require approved materials and specialist cleaning and assembly procedures.

Standards and What They Demonstrate

The Jointing Compound states conformity with BS EN 751-2:1997 and BS 6956-5:1992. BS EN 751-2 addresses non-hardening sealing materials for metallic threaded joints in contact with specified gas families and hot water in heating systems. BS 6956-5 covers jointing compounds for stated water, low-pressure saturated-steam and first- and second-family gas applications, including defined pressure, temperature, pipe-size and thread conditions.

A standard reference must be read with its classification, scope and the manufacturer's instructions. It does not mean that the compound is suitable for every gas, every water service, all thread sizes or any industrial chemical. For a regulated project, retain the current product certificate or declaration rather than relying only on the category description.

The anaerobic product refers to ISO 10964. That test compares the torque required to release anaerobic adhesives on threaded fasteners. It is useful for assessing locking or dismantling behaviour, but it is not a pipe-pressure approval, gas certificate or chemical-compatibility standard.

Preparing the Threads

1. Isolate, depressurise, drain and make the system safe using the procedure required for the conveyed medium.
2. Confirm that both fittings are metallic, correctly matched and within the sealant's permitted size and service range.
3. Remove old sealing material without damaging the thread profile.
4. Clean away oil, grease, scale, corrosion, swarf, dust and other contamination.
5. Inspect for burrs, cracking, distortion, cross-threading and excessive wear. Replace defective fittings.
6. Allow cleaning agents to evaporate fully before applying an anaerobic sealant.

Good preparation is essential. Applying more compound cannot compensate for insufficient thread engagement or mechanical damage. Cleaning materials must themselves be compatible with the pipework and intended service.

Applying VITCAS Pipe Jointing Compound

1. Use the paste as supplied unless the current instructions expressly require stirring.
2. Apply an even coating around the clean male thread.
3. Keep excessive material away from the first thread and pipe bore to reduce internal extrusion.
4. Assemble the mating fitting and tighten it using the correct tools and torque or engagement guidance.
5. Remove external excess and inspect the joint.
6. Test for soundness using the procedure appropriate to the system before it is put into service.

Do not add solvent, oil or another sealing product to alter the consistency. If fibre, hemp or PTFE tape is proposed as an additional material, confirm that the combination is explicitly permitted; combining unverified sealing systems can change assembly torque and invalidate approval.

Applying Anaerobic Liquid PTFE

1. Clean and degrease both metal threads, then allow them to dry.
2. Apply a continuous quantity around the male thread while avoiding uncontrolled excess inside the pipe.
3. Assemble promptly so the sealant is confined in the thread clearance.
4. Tighten the joint to the required alignment and engagement.
5. Observe the fixture and full-cure times applicable to the metals, gap and ambient temperature.
6. Carry out the specified pressure test only when the joint has developed the required sealing performance.

Sealant left outside the joint remains exposed to air and may stay liquid; this does not necessarily indicate failure of the material confined between the metal threads. Wipe away surface residue safely. If the joint is loosened after curing, dismantle it, clean the threads and apply fresh material before reassembly.

Pressure Testing and Commissioning

Every completed connection requires the leak or soundness test specified for the installation. The test medium, pressure, duration and acceptance criteria depend on whether the system contains water, gas, steam or compressed air. Never check a gas leak with a naked flame.

An initial low-pressure seal is not equivalent to a fully cured or approved working joint. Do not exceed the sealant, fitting or pipe rating during testing. Investigate any pressure loss rather than tightening a live or pressurised joint. After repair, repeat the full required test.

Dismantling and Maintenance

The non-hardening compound remains pliable, while the cured anaerobic sealant is described as having sufficiently low mechanical strength for conventional hand-tool dismantling. Ease of disassembly still depends on fitting size, corrosion, assembly torque and service history.

Once a joint has been disturbed, do not rely on the previous seal. Separate the fittings, remove old material, inspect and clean the threads, then reseal with fresh compatible compound. Repeated adjustment can damage thread engagement or introduce debris into the system.

Troubleshooting Leaking Threaded Joints

Observed problem	Possible cause	Required response
Leak immediately after assembly	Insufficient coverage, mismatched threads, contamination, poor engagement or damaged fitting	Isolate and dismantle the joint; inspect, clean and remake it rather than applying paste externally.
Anaerobic sealant remains uncured in the joint	Plastic component, excessive gap, low temperature, passive metal, contamination or insufficient curing time	Confirm substrate and gap suitability and consult the technical data for curing or activator requirements.
Fitting splits or distorts	Over-tightening, incompatible thread geometry or vulnerable plastic/metal fitting	Replace the fitting and correct the joint design or assembly method.
Leak develops during service	Excess pressure or temperature, vibration, chemical incompatibility, corrosion or mechanical movement	Take the system safely out of service and establish the root cause before resealing.

Storage and Safe Handling

• Read the current label, technical data sheet and safety data sheet before use.
• Keep containers closed when not in use and protect them from contamination.
• Store within the temperature range stated by the manufacturer and away from heat or direct sunlight.
• Wear the eye, skin and hand protection specified for the product and cleaning agent.
• Prevent sealant and cleaning residues from entering drains or the completed pipe bore.
• Dispose of unused product, contaminated wipes and empty containers according to local requirements.

Frequently Asked Questions

What does pipe jointing compound do?

It fills clearances and the spiral leakage route between mating metal pipe threads, helping the mechanically engaged joint form a watertight or airtight seal for approved media and operating conditions.

What is the difference between jointing compound and liquid PTFE?

The pipe jointing compound remains non-hardening and pliable. Liquid PTFE is a methacrylate-based anaerobic gel that cures after it is confined without air between close metal threads.

Which product withstands the higher temperature?

VITCAS Pipe Jointing Compound is listed to 200°C. The anaerobic Liquid PTFE product is listed to 150°C. Temperature alone is not sufficient for selection; media, pressure, thread and approval must also be checked.

What pressure is the jointing compound rated for?

The product page states a maximum of 7 bar. Confirm the permitted combination of pressure, temperature and medium, because the maximum values may not apply simultaneously to every service.

What is the pressure rating of Liquid PTFE?

Liquid PTFE provides an instant low-pressure seal but does not publish a numerical final pressure rating. Obtain the current technical data before specifying or pressure-testing the product.

Can these sealants be used on plastic threads?

Do not assume so. Both products are presented for metal threaded joints, and the anaerobic product requires metal surfaces to cure correctly. Some sealants and assembly torques can damage thermoplastic fittings.

Is VITCAS Pipe Jointing Compound suitable for natural-gas threads?

The product lists natural gas and states conformity with BS EN 751-2:1997. The exact installation must remain within the standard, product and regulatory scope and be completed and tested by a suitably qualified person.

Can the jointing compound be used for LPG?

The product lists LPG, while BS EN 751-2 covers specified third-family gases excluding LPG in liquid form. Confirm that the application is LPG vapour service and meets all current installation requirements.

Does Liquid PTFE have gas approval?

The product page lists gas as an application but does not state conformity with BS EN 751-1. ISO 10964 concerns torque testing of anaerobic adhesives and is not a gas-service approval. Obtain documentary confirmation before regulated gas use.

Can pipe jointing compound be used for drinking water?

Do not infer potable-water approval from a general water or non-toxic claim. Check for current WRAS acceptance or the specific drinking-water approval required for the project and jurisdiction.

Can the white compound seal steam pipework?

It is listed for low-pressure steam up to the published product limits. Confirm the permitted steam condition, pressure-temperature relationship, pipe size and standard classification before use.

Is Liquid PTFE the same as PTFE tape?

No. It is a curing anaerobic methacrylate sealant applied as a gel. PTFE tape is a non-curing strip wrapped around a thread and is covered by different product instructions and standards.

How large a thread gap can Liquid PTFE seal?

The product page states gaps up to 0.3mm. This limit cannot be used to justify sealing severely worn, incorrectly matched or damaged threads.

How quickly does anaerobic thread sealant cure?

The exact fixture and full-cure times are not published on the current page. Cure depends on metal type, temperature and gap, with approximately 20–25°C stated as the preferred curing range.

Can the system be pressurised immediately?

Only within the documented initial-seal and pressure-test conditions. An instant low-pressure seal does not mean that an anaerobic product has reached full cure or final performance.

Where should the compound be applied?

Apply it evenly around the clean male metal thread, controlling the quantity so excess is not pushed into the pipe bore. Assemble using the correct engagement and tightening method.

Can compound be applied externally to stop an existing leak?

No. Isolate and depressurise the system, dismantle the leaking connection, identify the cause, clean and inspect the threads, then remake and test the joint correctly.

Can pipe jointing compound be used in oxygen systems?

Not without explicit oxygen-service approval. Oxygen installations require verified compatible materials and specialist cleaning and assembly procedures.

Can these products seal oil, fuel, refrigerant or chemical lines?

Only with written confirmation for the exact medium, concentration, pressure and temperature. The current pages do not provide a comprehensive chemical-compatibility or refrigerant-approval table.

Can a sealed joint be dismantled and reused?

The fittings may be dismantled if they remain serviceable, but the old seal should not be reused. Remove the previous material, inspect and clean both threads, then apply fresh approved compound before reassembly and testing.

Who should install pipe jointing compound on gas pipework?

Gas work must be completed by a person legally competent for the system. For UK domestic gas work, use a Gas Safe registered engineer qualified for the relevant appliance, installation and gas type.