NBS Plumbing & Heating
All Guides
Plumbing4 min read

Low or High Water Pressure: Causes and Fixes

Poor water pressure in showers and taps is frustrating. Here's why it happens and what the solutions are for different types of home.

Water pressure problems affect millions of UK homes. Whether your shower is a trickle or your combi boiler keeps showing a low pressure warning, the causes and solutions differ. Here's how to diagnose and address pressure issues.

Boiler pressure vs mains water pressure

These are separate systems and often confused:

  • **Boiler pressure** refers to the pressure of water circulating in your central heating system (the closed circuit). Measured on your boiler gauge in bar.
  • **Mains water pressure** refers to the pressure of water coming from the street supply into your property taps and appliances.

    • Low boiler pressure

    If your boiler gauge reads below 1 bar, you have low boiler pressure. This typically causes the boiler to lock out. Causes include:

  • A small leak somewhere in the heating system
  • Radiators that have been bled without re-pressurising
  • A faulty pressure relief valve that's been releasing water

    • **Fix:** Re-pressurise through the filling loop (follow your boiler manual). If pressure keeps dropping, call an engineer — there's a leak somewhere.

    Low mains water pressure

    Low pressure at taps and showers can be caused by:

  • **Partially closed stopcock or service valve:** Check the stopcock under the sink is fully open.
  • **Blocked filter or scale build-up:** Aerators on taps and shower heads get blocked with lime scale — unscrew and clean them.
  • **Old pipework:** 15mm copper pipework throughout an older house restricts flow. Upgrading to 22mm on supply runs improves pressure significantly.
  • **Supplier pressure issue:** Call your water supplier to check if there are known issues in your area.
  • **Pressure reducing valve (PRV):** Most modern properties have a PRV fitted at the mains entry. These can fail and restrict supply — a plumber can test and replace.

    • High water pressure

    Mains pressure above 4 bar can cause noisy pipes (water hammer), dripping taps, and appliance damage. A PRV set to 2.5–3 bar protects the system. If your water pressure seems very high (power like a pressure washer from an open tap), have a plumber fit or adjust your PRV.

    Contact NBS Plumbing & Heating for pressure diagnosis across Sutton Coldfield and Birmingham — **07507 133204**.

    More Guides

    Plumbing

    Bathroom Renovation: The Plumbing Guide

    Planning a bathroom renovation? Here's what the plumbing phase involves, what questions to ask your plumber, and how to avoid costly mistakes.

    Need a Plumber or Heating Engineer?

    Covering Sutton Coldfield, Birmingham and surrounding areas.

    Call 07507 133204Get a Free Quote