What is normal UK mains water pressure?

UK mains water pressure typically ranges from 1 to 5 bar, with most properties receiving 2-4 bar. Water companies are required to provide a minimum of 1 bar (10m head) at the external stop tap. Pressure can vary during the day — it is usually highest overnight and lowest in early morning and early evening when demand peaks. Pressure above 5 bar may require a pressure reducing valve (PRV) to protect appliances.

What pressure is UK natural gas supplied at?

Natural gas is supplied to UK domestic properties at 21 mbar (approximately 0.021 bar or 8.4 inches water gauge). This is measured at the meter. The working pressure at appliances should be 19.5-21.5 mbar. Gas pressure testing is done at higher pressures: 300mm water gauge (approximately 30 mbar) for soundness testing of low-pressure installations. Only Gas Safe registered engineers may work on gas systems.

What does "metres head" mean?

1 metre head is the pressure exerted by a column of water 1 metre high, equal to approximately 0.098 bar or 9.81 kPa. It is commonly used in plumbing for calculating the static pressure from a cold water tank in a loft — a tank 10m above a tap provides approximately 1 bar of pressure. Pump performance curves also use metres head to show the relationship between flow rate and pressure.

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Pressure Unit Conversions — Bar, PSI, kPa

Pressure unit conversions for UK plumbing, heating and gas installations. Bar, psi, kPa, mbar, metres head and mmHg with common reference values.

Pressure Conversion Table

Unit	bar	psi	kPa	mbar	m head
1 bar	1	14.504	100	1,000	10.2
1 psi	0.06895	1	6.895	68.95	0.703
1 kPa	0.01	0.1450	1	10	0.102
1 mbar	0.001	0.01450	0.1	1	0.0102
1 m head	0.0981	1.422	9.81	98.1	1

Common UK Pressure Reference Values

Application	Typical Pressure	In bar	In psi
Mains water (min at stop tap)	10m head	1.0	14.5
Mains water (typical)	20-40m head	2-4	29-58
Combi boiler DHW	—	1-3	14.5-43.5
Sealed heating system	—	1.0-1.5 (cold)	14.5-21.8
Sealed system PRV setting	—	3.0	43.5
Natural gas (domestic)	21 mbar	0.021	0.30
LPG (regulated)	37 mbar (propane)	0.037	0.54
Gas soundness test	30 mbar	0.030	0.44
Tyre pressure (car)	—	2.0-2.5	29-36
Atmospheric pressure	760 mmHg	1.013	14.70

See the Flow Rate Conversions, the Water Velocity Standards, and the UK Pipe Sizes.

How We Calculate This

Frequently Asked Questions

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Last updated: April 2026

All calculations are estimates. Verify with your supplier.