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The gas flowing to your boiler or cooker is not at the same pressure as in the transmission pipeline. Between the service connection and the appliance there is a key device – the domestic gas pressure regulator. We will explain the pressure levels used in the gas network, what pressure your appliances require, and how to choose a regulator that safely reduces the pressure and keeps it at a stable value.
Author: Michal Chytka - Gas Pressure Regulator Product Specialist
Natural gas enters the Czech Republic through high-pressure pipelines via transfer stations at the border, where the pressure reaches up to one hundred bar and millions of cubic metres are transported. For the gas to reach appliances in our homes, its pressure must be reduced gradually in several stages. The distribution system therefore operates with several pressure levels:
| Pressure level | Range | Where you will encounter it |
|---|---|---|
| Low pressure (LP) | up to 5 kPa (0.05 bar) | domestic internal pipework and appliances |
| Medium pressure (MP) | above 5 kPa up to 0.4 MPa (4 bar) | medium-pressure gas main - street distribution |
| High pressure (HP) | above 0.4 MPa up to 4 MPa | main high-pressure distribution gas pipelines |
| Very high pressure (VHP) | above 4 MPa | international transit transmission system |
Quick unit conversion: 0.1 MPa = 1 bar = 100 kPa = 1000 mbar. Low pressure of 5 kPa therefore corresponds to 0.05 bar. A regulator outlet pressure of 21 mbar is 2.1 kPa, or 0.021 bar.
Regulating stations in our territory first reduce high pressure to medium pressure, usually to a value of up to 4 bar (400 kPa). However, for installations in family houses, apartment buildings and smaller commercial premises, the pressure must be reduced once more. To low pressure, i.e. up to 5 kPa (0.05 bar), or to the millibar values mentioned in the heading, specifically up to 50 millibars. It is precisely for this final step that a domestic gas pressure regulator is required.
Common household appliances – gas boilers, cookers, instantaneous water heaters – available on the Czech and Slovak market are designed for a nominal inlet overpressure of around 2 kPa (20 mbar). Domestic regulators therefore typically maintain the outlet pressure at 21 mbar, which corresponds to 2.1 kPa. This value is the standard for domestic natural gas pipework in the Czech Republic.
In addition to pressure, flow rate is also important, i.e. the volume of gas the appliance requires per unit of time. This is stated in cubic metres per hour (m³/h) and can be found on the appliance rating plate and in its documentation. In households it most commonly ranges up to 6 to 10 m³/h. The regulator must be sized so that it can deliver the required flow rate without the outlet pressure dropping below the safe limit.
If the network upstream of the main gas shut-off valve (HUP) of your house or business is not already low pressure, a domestic regulator is essential. It reduces and at the same time stabilises the pressure from the service connection to a value that is safe for the appliances and for the building as a whole. Without regulation, pressure fluctuations in the distribution network could damage appliances or cause a dangerous gas leak.
In practice, the safety of a gas installation rests on three pillars. The first is the safety features built directly into the regulator – the safety slam-shut valve and the relief valve. The second is gas leak detectors (for example the EVIKON E2630-LEL range), which reliably warn of a leak before it reaches a dangerous concentration. The third is solenoid valves (PEVEKO) and shut-off valves (BAP), which immediately interrupt the gas supply in an emergency. Larger installations always use them, but even for a family house there are PEVEKO solenoid valves whose dimensions and parameters are suitable for domestic pipework.
Installation, inspections and any repairs to regulators may only be carried out by trained personnel from specialist companies or gas utilities. DIY work on gas installations is not permitted.
Most domestic regulators are direct-acting, spring-loaded regulators. The principle is elegantly simple: the spring and diaphragm setting determines the outlet pressure. The relief valve prevents the set value from being exceeded, while the safety slam-shut device immediately closes the inlet if the pressure moves outside the safe range. Once the cause has been checked, the regulator can only be returned to service manually – it never reopens by itself.
This is well illustrated by the HUTIRA B NG domestic regulator, designed for domestic natural gas service connections from medium-pressure networks. It operates in two stages of pressure reduction: the first stage maintains a constant outlet pressure regardless of fluctuations in the inlet pipeline pressure, while the second stage keeps the outlet pressure constant even when the flow rate changes. The result is a stable value of 21 mbar across the entire range of inlet pressures.
The shut-off device of the B NG regulator interrupts the gas flow in three situations: when the set flow rate is exceeded (for example in the event of damage to the outlet pipework), when the outlet pressure drops below the set value (excessive consumption), and when the inlet pressure drops below the specified limit (fault in the inlet gas pipeline – this function only applies if gas is flowing at the time). After tripping, the regulator must be restarted manually using the start button, so the supply can never be restored automatically.
The design also includes an integrated monitoring relief valve protecting appliances against an increase in outlet pressure – excess gas is discharged through a vent opening fitted with a stainless steel mesh. At the inlet there is a bronze filter to trap impurities. All internal parts are in continuous motion, which prevents dirt build-up and seizure of the mechanism, so the regulator responds reliably even after a long period of operation.
Technical parameters:
When selecting a domestic regulator, work from three pieces of information. The first is the pressure in the service connection – check with the distributor whether it is medium pressure and within what range. The second is the required flow rate, i.e. the total consumption of all appliances in m³/h. For a standard family house with a boiler and cooker, the B6 NG version (up to 6 Nm³/h) is usually sufficient; for higher demand, a larger boiler room or multiple appliances, choose the B10 NG (up to 10 Nm³/h). The third is the connection type and design (angle, straight, kiosk-mounted), so that the regulator fits your assembly. In addition, the angle version of the B NG has the same connection dimensions as FRANCEL type B and Fisher B NG regulators, so they can be replaced without modifying the pipework.
Tip: Not sure which version to choose? Add up the nominal flow rates of your appliances from their rating plates and include a reserve margin. If you are unsure, we will be happy to help you choose – get in touch.
The internal pipework in a home operates at low pressure up to 5 kPa (0.05 bar). Domestic regulators typically maintain the outlet pressure at 21 mbar (about 2.1 kPa), which matches standard gas appliances in the Czech Republic.
Yes, if the network upstream of the main gas shut-off valve is not already low pressure. In most service connections, the network is medium pressure (up to 4 bar), which must be reduced to a safe value before the appliances.
They differ in maximum flow rate: the B6 NG handles up to 6 Nm³/h, while the B10 NG handles up to 10 Nm³/h. In addition, the B10 NG reaches full flow rate at a lower inlet pressure. For a typical family house, the B6 NG is usually sufficient; for higher demand, choose the B10 NG.
No. On B NG regulators, the outlet pressure is fixed at the factory to 21 mbar and is not user-adjustable. This is the standard value for domestic natural gas pipework in the Czech Republic.
If the inlet pressure drops below the specified limit (provided gas is flowing at the time), the shut-off device automatically interrupts the supply. Once the pressure is restored, the regulator does not reopen by itself – it must be restarted manually using the start button. This prevents uncontrolled flow when the supply is restored.
Installation, inspections and repairs to regulators may only be carried out by trained personnel from specialist companies or gas utilities. DIY work on gas installations is not permitted.
The standard B NG version is designed for temperatures from −20 to +60 °C. For locations with more extreme frost, the manufacturer offers a version for temperatures below −20 °C on request.
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