Mains Pressure Gauge (Screw-On) – Test Your Water Pressure at Home
A screw-on mains pressure gauge is a simple, affordable tool that lets you measure the exact bar reading of your incoming cold water supply. It is the first step in diagnosing low pressure throughout your home, overnight pressure drops, or verifying whether your water company is meeting the legal minimum.
What Does a Mains Pressure Gauge Do?
In a standard UK home, a screw-on pressure gauge is used to:
- Measure Static Pressure: Shows the pressure in your mains supply when no taps are running — typically between 1 and 4 bar in the UK.
- Measure Dynamic Pressure: Shows the pressure drop under live flow, revealing how much your supply degrades when taps or appliances are in use.
- Provide Evidence: Gives a hard number you can quote when reporting a low pressure fault to your water supplier.
Common Reasons to Use One
A pressure gauge is particularly useful if you are experiencing any of the following:
Choosing the Right Size
UK screw-on pressure gauges connect via a standard BSP (British Standard Pipe) thread. The most common connection sizes you will encounter are:
| Connection Size | Thread Standard | Typical UK Attachment Point |
|---|---|---|
| ½ inch BSP | Male or Female | Washing machine fill valve, kitchen tap tail |
| ¾ inch BSP | Male or Female | Outdoor garden tap, stopcock outlet |
Most general-purpose kits sold in the UK include a ¾ inch BSP adapter as standard, making them compatible with the vast majority of outdoor taps. Check the thread before purchasing if attaching directly to an internal valve.
Where to Buy a Pressure Gauge in the UK
Screw-on pressure gauges are widely stocked and typically cost between £8 and £25. Kits that include multiple BSP adapters offer the best flexibility.
| Retailer | Stock Status | Benefit | Link |
|---|---|---|---|
| Screwfix | In Stock | Click & collect same day | View Range |
| Amazon | Available | Arctic Hayes WPG1-AMZ | Check Stock |
How to Take a Mains Pressure Reading
Getting an accurate reading takes under five minutes and requires no special skills. The outdoor tap is the easiest connection point for most homes.
Find a Suitable Tap or Valve
The most convenient attachment point is an outdoor garden tap. Alternatively, you can disconnect the hose from your washing machine's hot or cold fill valve and attach the gauge there. Make sure the tap or valve is fully closed before attaching.
Screw On Hand-Tight
Thread the gauge adaptor onto the tap outlet or valve connection. Hand-tighten firmly. Most gauges include a rubber washer in the fitting — do not over-tighten, as this can deform the seal and cause a drip around the connection.
Open the Tap Slowly — Then Close It
Turn the tap on fully, then close it again. The needle will settle on your static pressure — the pressure in the pipe when nothing is flowing. In most UK homes this reads between 1.5 and 4 bar. Record this number.
Open the Tap and Read Under Flow
Open the tap fully while the gauge is still connected. The reading will drop — this is your dynamic pressure. A significant drop between static and dynamic readings (more than 1 bar) often indicates a restriction in your supply pipe or a partially closed internal stopcock.
Leave the Gauge Fitted Overnight
If you suspect your pressure drops specifically at night, leave the gauge attached to the outdoor tap with the tap open and check the reading first thing in the morning. A reading below 0.7 bar means your water supplier is potentially falling below the legal minimum set by Ofwat and you have grounds to file a formal complaint. See our full breakdown of why UK water pressure drops at night for what to do next.
💡 Pro Tips for an Accurate Reading
- Test at night (11 PM–5 AM): UK water companies often reduce network pressure overnight. Testing at this time gives you the worst-case reading for your property.
- Turn off all appliances: Dishwashers, washing machines, and running toilets all reduce dynamic pressure. For a true static reading, ensure nothing is drawing water inside the property.
- Check the gauge range: Most domestic gauges read 0–10 bar or 0–6 bar. Either range is fine for a UK mains test. Avoid industrial gauges scaled to 25 bar — the resolution makes low readings hard to distinguish.
- PTFE tape is not needed: The gauge's internal rubber washer is sufficient. Adding PTFE to a rubber-seated connection can actually cause the fitting to leak by preventing the washer from sitting flush.
- Low boiler pressure is separate: If your boiler pressure is dropping overnight on the heating circuit gauge, that is a closed-loop central heating issue — not a mains supply problem this gauge will detect. Check our boiler pressure guide for that fault.