What is normal mains water pressure in the UK?

UK mains water pressure typically ranges from 1.0 to 4.0 bar, with most properties receiving 2-3 bar. Water companies are required to provide a minimum of 1.0 bar at the boundary stop tap (the property boundary). Pressure varies by location, time of day, and demand in the area. You can check yours with a pressure gauge on an outside tap.

How do I calculate gravity water pressure?

For gravity-fed systems (cold water tank in the loft), pressure depends on the vertical height between the tank and the outlet. Every 1 metre of height (head) provides 0.1 bar of pressure. So a tank 3 metres above the shower gives 0.3 bar — which is low and often insufficient for thermostatic showers or rain heads.

What pressure do I need for a thermostatic shower?

Most thermostatic shower valves require a minimum of 0.5 bar (some need 1.0 bar). Gravity-fed systems often can't provide this without a pump. Combi boilers and unvented cylinders typically provide 1.5-3.0 bar, which is adequate. Always check the manufacturer's minimum pressure requirement.

Why is my water pressure lower upstairs?

On mains-fed systems, water pressure decreases by approximately 0.1 bar for every metre of height. A bathroom 6m above the mains entry point loses about 0.6 bar. Additionally, pipe friction from longer runs and more bends further reduces pressure. This is why first-floor bathrooms sometimes have lower shower pressure than ground-floor ones.

How can I improve my water pressure?

Options include: (1) Install a shower pump (for gravity systems), (2) Switch to a combi boiler or unvented cylinder for mains pressure throughout, (3) Reduce pipe friction by using larger diameter pipes or shorter runs, (4) Install a mains booster pump (check with your water company first), (5) Ensure the stopcock is fully open and pipes are not furred up.

TradeCalcs

Water Pressure Calculator — Is My Pressure Sufficient?

Calculate water pressure from head height or mains supply, including pipe friction losses. Check if your pressure is adequate for showers and taps.

System Type

Determines how pressure is generated

Fixture to Check

Each fixture has a minimum pressure

Mains Pressure

Typical UK: 1.0-4.0 bar. Check with a gauge.

Pipe Run Length

Total pipe length from source to fixture

Pipe Diameter

15mm, 22mm or 28mm

Number of Elbows/Bends

Each elbow adds ~0.6m equivalent length

How We Calculate This

This calculator estimates the effective water pressure at a fixture by starting with the available pressure (from gravity head or mains supply) and subtracting friction losses through the pipe run.

The formulas

Gravity pressure (bar) = Head height (m) × 0.1
Equivalent pipe length = Actual length + (Elbows × 0.6m)
Pressure loss = Equivalent length × Friction factor
Effective pressure = Available pressure - Pressure loss

Fixture minimum pressures

Basin/bath tap: 0.1 bar
Kitchen tap: 0.5 bar
Mixer shower: 0.1 bar
Thermostatic shower: 0.5 bar
Power shower: 1.0 bar
Electric shower: 1.0 bar
Rain head shower: 1.5 bar

Note: This is a simplified calculation. Real-world pressure depends on many factors including pipe condition, simultaneous demand, and water company supply pressure. For accurate results, use a pressure gauge at the fixture location.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Verify with your supplier.