boiler pressure hints & tips

Boiler Pressure Hints and Tips 

Every boiler and central heating system requires a bit of TLC, in addition to the yearly service. 

This includes making sure the pressure in the system is correct and bleeding the radiators (getting air out of the system) Your boilers user guide will have instructions on how to do this simple task, don't worry if you don't have them, most boiler manufacturers have all their manuals available online. A list of the most common ones will be at the bottom of this page. 

Below are some frequently asked questions that will also guide you through the process of checking and pressurising your system. If you still can't get your boiler to work once you have completed these tasks, or you need help with system controls please don't hesitate to contact us.

Frequently Asked Questions;

How do I find out what the pressure of my heating system is? 

Combination and System boilers will have a pressure gauge either on the front of the boiler or just below on the heating pipework. The gauge will look something like the picture. 

Heat Only (or Regular) boilers installed on a pressurised system will have a pressure gauge installed on the pipework. 

Open vented systems (Tank in loft) are not pressurised and do not have a pressure gauge. 

What should the pressure be? 

The normal pressure of a heating system when cold is 1-2 bar. Lots of boilers have a green (safe zone) along with the normal numbers. 

If my pressure is low, how can I increase it? 

If your water pressure drops below the lowest pressure set by the manufacturer, your boiler will not work until the pressure has been increased. You can carry out this simple maintenance task yourself without the need of an engineer visit. Although if the problem returns rather quickly you will need to have an engineer visit to investigate the cause further. 

In your manual, you will find a guide to carrying out this task or you can look at the manufacturers website. We are also more than happy to talk you through this process on the phone at no cost to you. 

How to increase pressure: 

1) The filling loop will be on the boiler itself or on the pipework below. The filling loop is made up of 3 parts, 2 ball valves with either taps or slotted screw heads (in line with pipe = open) and 1 copper pipe or braided hose. And normally attaches the cold-water pipe to the central heating flow pipe. 

2) Fully open one of the taps, then slowly open the other until you can hear water, and see gauge moving. 

3) When the needle on the gauge is between 1.0 and 2.0 bar, turn off both taps. 

4) Bleed radiators (a guide is below) 

What causes the pressure drop? 

Over time it is not unusual for a central heating system to lose a bit of pressure. But if the pressure is dropping regularly then this could indicate a leak on the system or the pressure vessel needs looking at. 

Bleeding radiators 

If you have just put more pressure in your system or your radiators are cold at the top, then you need to bleed the air out.  

1) Before starting to bleed your radiators, make sure your heating is off and the system is cold. Some modern radiators can be bleed using a small slotted screwdriver, others need a radiator key available from most DIY stores. 

2) To bleed your radiators. Always start down stairs at the radiator furthest away from the boiler working your way back. 

- Attach the radiator key to the square section in the centre of the radiator bleed valve (this can be found at the top left or right of the radiator) 

- Have a cloth or strong tissue paper you can place under the key 

- Turn the radiator key slowly in an anti-clockwise direction 

- If air is escaping you will hear a hissing sound 

- Once all the air has escaped, water will start to leak from the valve 

- Close the valve quickly  

(Repeat this for all radiators in the property) 

3) Check the pressure of the heating system, and add pressure if needed 

If after doing all this, you are still having the problem and think you may be in need of a boiler repair and service then please don't hesitate to call us on 023 9309 2485 

We cover Portsmouth, Fareham, Havant and surrounding areas.