Plumbing & Heating FAQs

Here you can access frequently asked questions about our plumbing and heating products, alongside information to help you diagnose and resolve any technical issues. We also offer lifetime technical support, so if you cannot find what you are looking for, please contact our helpdesk.

74 Total available results

Yes, underfloor heating systems (UFH) are ideal for retrofitting in existing properties. JG Underfloor offers a range of different options depending on your project needs. For more information, visit our system selector page or speak to one of our UFH experts.

Yes, air source heat pumps (ASHP) and ground source heat pumps (GSHP) are ideal for underfloor heating systems (UFH). In order to integrate underfloor heating systems (UFH) efficiently, please refer to the heat pump manufacturer's instructions.

There are a variety of components that make up the underfloor heating system (UFH). For more information on the best system for your project and the required components, speak to one of our UFH experts.

Yes. Please contact one of our UFH experts.

No, you should never do this as it can damage the screed.

First, ensure the thermostat is showing a flame symbol - indicating that the heat source has been turned on. Next, ensure that the boiler is firing correctly and if confirmed ensure that the pump indicating light on the UFH manifold is also on. The final check is to ensure that the LED for the specific flooring zone, positioned on the front of the wiring centre is showing as on. If all of these checks confirm that there are no issues, then this may indicate that the actuator pin valve, found on the return manifold bar, is stuck in the down position, closing the circuit, and therefore preventing circulation. We would recommend having this replaced by a qualified plumber or heating engineer. 

Yes, underfloor heating systems (UFH) can be used upstairs. JG Underfloor offers a range of different options depending on your project needs. For more information, visit our system selector page or speak to one of our UFH experts.

Yes, you can tile directly on the JG Lowfit Fibre Mesh panel, other products require a separation layer such as a tile backer board.

When the pipes are installed correctly, there should be no joints in the floor, so the risk of any leak is extremely low. However, if a leak is found, please contact your local heating engineer to locate and repair it.

No, modern levelling compounds used as a screed layer are designed to expand and contract without cracking. The design and materials used in our JG Layflat and PEX pipe materials are very resilient and come with a 50-year guarantee for extra peace of mind.

There are a number of different reasons why the complete underfloor heating system (UFH) is not working. The boiler may not be functioning correctly, or a motorised zone valve isn't opening correctly. Please contact our Technical Helpdesk for assistance in diagnosing any specific operational issues.

Most floor coverings will work with underfloor heating systems (UFH) provided that they don’t exceed 2.5 Tog. For more detailed information, please speak to one of our UFH experts.

All underfloor heating systems (UFH) systems are energy efficient, however, generally speaking, a screed UFH system offers marginally better performance. For more information, visit our system selector page or speak to one of our UFH experts.

It's not advisable, because any heating system, be it radiators or underfloor heating systems (UFH), works more efficiently when heat is supplied only where it is needed. As an example, it is rarely necessary to heat a bedroom during the day and a living room in the early morning. You can maximize fuel efficiency and keep heating costs low by controlling the heating room by room.

Yes, we offer a free underfloor heating (UFH) design service. Please contact one of our UFH experts.

Yes, underfloor heating systems (UFH) pipe can be used in cooling applications. Please contact one of our UFH experts for more advice.

This may indicate a faulty room thermostat or electronic actuator head if the issue is only in one zone. We would recommend having the associated wiring checked by a qualified electrician who will be able to identify the fault safely. Please contact our Technical Helpdesk for assistance in diagnosing any specific operational issues.

Yes, however, we advise a combined tog value of underlay and carpet no greater than 2.5.

The costs of installing underfloor heating systems (UFH) have become much more comparable to traditional heating systems. Plus, the improved energy efficiency of underfloor heating also reduces the overall cost of the system. For more information, request a free estimate or speak to one of our UFH experts.

Yes, our JG Underfloor Heating Controls can be controlled via mobile and tablet from anywhere, provided there is an internet connection.

All our 15mm underfloor heating systems (UFH) use regular JG Layflat pipe meaning there is zero wastage, anything left over from the underfloor heating system's (UFH) installation can be used elsewhere. Our low-profile range, JG LowFit uses 12mm JG Layflat pipe. Please contact one of our UFH experts for more advice.

Underfloor heating systems (UFH) can be installed at any time of year, certain precautions are advised in winter to protect the system from freezing. Please contact one of our UFH experts for more advice.

Yes, underfloor heating systems (UFH) work effectively with most types of vinyl and linoleum. However, it should be noted, vinyl and linoleum flooring offer lower heat resistance due to its thinner construction. For further information on compatibility with your chosen floor covering, please speak to one of our experts.

This may indicate an issue with the pump relay connection on the UFH wiring centre. Please contact our Technical Helpdesk for assistance in diagnosing any specific operational issues.

Yes, however, extra care may be required depending on the type of substrate. For more information, please speak to one of our UFH experts.

Underfloor heating systems (UFH) circulate water at a lower temperature than radiators, so assuming the building meets modern building standards, and the UFH system is set according to JG Underfloor's design parameters, then underfloor heating systems are cheaper to run.

All JG Underfloor heating systems (UFH) are manufactured to the highest industry standards and are rigorously tested by our quality assurance team. For extra peace of mind, our fittings and pipe come with a 50-year guarantee and our manifolds, control packs and JG Underfloor Heating Controls with a 2-year guarantee.

Underfloor heating systems (UFH) are suitable for the most common types of heat sources. However, for optimal efficiency, it is most effective when used in conjunction with modern renewable heat sources like ground or air-source heat pumps. For further clarification on compatibility please speak to one of our experts.

Yes, however underfloor heating systems (UFH) is not specifically designed for drying towels.

This is normally decided by the architect and builder based on the structural loading of the building. Speedfit underfloor heating systems (UFH) is suited for all modern applications.

Yes, however, this is not an ideal solution as the latent heat circulating through the radiator can prevent the underfloor heating system's (UFH) thermostat from switching the system on.

The JG Underfloor guarantee provides protection from any manufacturing faults or defects.

Underfloor heating systems (UFH) are commonly retrofitted using existing boilers, however, the output capacity may require the pipe size to be reduced, as well as the working flow rate for each heating zone. The flow rate should be calculated by a qualified heating engineer to ensure maximum efficiency and performance. For further guidance, please speak to our experts.

Yes, underfloor heating systems (UFH) are ideal for use in new build properties. JG Underfloor offers a range of different options depending on your project needs. For more information, visit our system selector page or speak to one of our UFH experts.

Yes, gas boilers are idea for underfloor heating systems (UFH).

This will depend on how often the UFH system is maintained and the environment where the heating controls, manifold and wiring centre are installed. It's essential that these components are housed in areas where accidental damage is unlikely to occur. We recommend that the system is checked every 12 months by a qualified heating engineer to ensure that it is working correctly and efficiently.

If a system is designed and installed correctly, the floor surface temperature would normally be between 25-29 degrees, which is about the same temperature as the palm of your hand.

A low-profile underfloor heating system (UFH) such as the JG LowFit range is recommended when a low floor height build-up is required. JG LowFit includes pipe fixing systems for both solid and timber floors that ensure the height of the floor is kept to a minimum without impacting system performance. For further guidance, please speak to one of our experts.

Yes, oil boilers are ideal for underfloor heating systems (UFH).

Yes, as it ensures any pipework within the kitchen units are protected from freezing. However, this isn't essential, as it is often difficult to do when retrofitting underfloor heating systems (UFH) in an existing kitchen.

Yes. Please contact one of our UFH experts.

This issue has been mitigated thanks to modern underfloor heating systems (UFH) design, however, it can still be the case with thick concrete slab flooring. Modern systems and methods mean underfloor heating systems (UFH) heat-up times are comparable to that of radiators.

Underfloor heating systems (UFH) compatible with 15mm pipe are predominately the first choice for new build projects, as when sized correctly with the chosen heat source, it heats up marginally quicker than 12mm pipe. However, 12mm pipe systems are more suited to retrofit projects as they provide a lower overall floor height build-up. For further guidance, please speak to one of our experts.

Yes, electric boilers are suitable for use with underfloor heating systems. For further guidance, please speak to our experts.

When connecting to copper pipe, the minimum distance to make a solder connection on the copper pipe inserted into a Speedfit fitting is 450mm (18 inches). To prevent damage, you must ensure any residual flux solder does not come into contact with the fitting. A pipe insert is not required when connecting Speedfit fittings to copper pipe.

No, the water temperature in a solid fuel boiler is very difficult to control and often fluctuates. Water temperature could run beyond the maximum temperature parameters that JG Speedfit is tested to.

Yes, they are suitable for this application.

Speedfit is suitable for cold water mains (indirect and direct), central heating and hot water systems (including unvented cylinders). Some Speedfit valves and tap connectors are only suitable for hot water systems, so always check the product packaging or manufacturer’s website before installation.

Yes, but only if the pipe and fittings are compatible. Compression fittings with a short tube stop depth or brass olives should not be used with Speedfit pipes. Use a standard pipe insert (TSM) and follow the instructions of the compression fitting manufacturer when connecting to plastic pipework. The connection should not need more than 2 full turns after the olive has gripped the pipe. JG Speedfit recommends using soft copper olives, always ensure the nut and olive are in place before inserting the pipe insert.

In accordance with best practices, a hydraulic wet test should be performed after a plumbing system installation is completed and ensure that all connections to boilers, radiators, and sanitary ware are capped or plugged. When the system has been filled with water, it should be tested at 2 bar for 10 minutes followed by 10 bar for 10 minutes to check for leaks. The test for underfloor heating systems (UFH)  should be 6 bar for 10 minutes prior to screed curing. The system should be filled during the screeding process to ensure the pipework isn't damaged during the drying process.

Yes, as long as the correct manufacturer's pipe insert is used. However, JG Speedfit fittings are designed and tested to be compatible with JG Speedfit pipe. JG Speedfit cannot guarantee the specification of other manufacturers' pipe therefore mixing JG Speedfit with Hep2O is not advised.

The Superseal Insert (STS) has a dual O-Ring, which provides a greater seal than a standard Insert. When combined with a Speedfit fitting, both the fitting and Superseal insert form a unique multi seal.

The Standard Insert (TSM) does not have an O-Ring and therefore allows more pipe into the fitting, making it suitable when connecting Speedfit pipe to compression fittings.

Yes, the same as copper pipe, insulation should comply with BS EN 806 standards.

No, however, we do supply a range of air and pneumatics fittings that are suitable for this application. Visit our compressed air range by John Guest, for more details.

PB pipe is more flexible than the PEX, this is because there is less memory in the coil, making it easier to handle on site. Both versions are barrier pipes and can be used for the same types of applications.

Yes, Speedfit is suitable in this situation.

No, a minimum 1 metre run of copper pipe must be installed between the boiler and the Speedfit system, as per BS5955 Part 8 regulations.

No, tools are not required for JG Speedfit fittings. For the Twist & Lock range, turn the screwcap on the fitting to the unlocked position. Push the collet square against the face of the fitting using your fingers. With the collet held in position, the pipe can be removed.

For standard fittings, push the collet square against the face of the fitting. With the collet held in position, the pipe can be removed.

Yes, Speedfit fittings and pipes can be used to plumb in a power shower. Always be sure to follow the power shower manufacturers' installation guidance and instructions.

Yes, Speedfit is suitable in this situation.

Yes, Speedfit pipe and fittings can be laid in concrete and masonry providing these are installed in conduit pipe with access boxes for the fittings. This is to enable the pipe to expand and provide accessibility for both the pipe and fitting. Insulation is also recommended to protect against heat loss and the effects of frost.

Yes, Speedfit fittings and pipe comply with the Water Regulations Advisory Scheme (WRAS).

No, Speedfit pipe and fittings have not been tested or approved for this application. Continuously operated re-circulating systems (secondary hot water circulation/ring main installations) are very different from conventional hot water supply and central heating systems found in domestic properties.

Yes, the valve has a directional flow arrow to indicate the correct water pathway through the valve. However, JG Speedfit fittings can be installed in any orientation.

Yes, however, the insert should be selected based on the fitting type. If using JG Speedfit Polybutylene Layflat, or PEX pipe with JG Speedfit Twist & Lock fittings we recommend using the JG Speedfit Superseal Insert which offers a multiseal connection. If installing the pipe with standard-type JG Speedfit fittings, then a Standard Insert is required. Both inserts ensure a tight leak-proof connection.

Speedfit fittings can be used with plastic barrier pipe or copper pipe. Speedfit cannot be used with stainless steel pipe.

Yes, as long as the collets remain sharp and O-Rings are inspected for cleanliness and the fitting is in good working order it can be reused.

A kink could eventually damage one of the layers that make up the construction of the pipe and could ultimately lead to a leak. If there is a kink in the pipe and the pipe wall is damaged then it is best to cut the section or pipe out.

Although the Polybutylene and PEX pipe have insulating properties, if there is a risk of pipe freezing then yes, the same as copper pipe. If used on central heating systems then insulating is essential to prevent heat loss through the pipe. For further guidance on minimum distances the insulation should be fitted to a heat source, please refer to Part L Building Regulations.

See table below for different applications and maximum temperatures and pressures:


Usual working temperature °c

Maximum working temperature °c

Maximum working pressure, bar

Cold water
(inderect and direct mains)




Central heating


105, short term malfunction at 114


Hot water
(including unvented cylinders)




NB: High temperatures: Speedfit fittings suitable for central heating systems can withstand temperatures up to 114°C intermittently for short periods. Speedfit fittings shown as not suitable for central heating systems are used primarily on the domestic hot and cold water systems with temperatures of up to 65°C.

Speedfit is a reliable plastic push-fit plumbing and heating system that is fast and simple to install, without the need for tools. As well as being a complete plumbing and heating system (pipes, fittings and valves), Speedfit products can also be used separately for repair, maintenance and improvement work.

Yes, either a Speedfit standard or Superseal insert is required to ensure that the ends of the plastic pipe are kept nice and round, and to minimise any loss of shape which can occur when cutting the pipe.

Yes, Speedfit pipes can be fed through both masonry and plasterboard/stud walls. If pipework needs to go through plasterboard walls then collet covers/clips should be used on all Speedfit fittings connected to the pipework behind the wall. If a Speedfit pipe is to be fed through holes in masonry or concrete then we advise the use of Speedfit conduit pipe to comply with water regulation schedule 2.7 and BS8000 : Part 15 which states that all pipework should be removable for possible future replacement.

No, there is no CE mark guidance for pipe work.