We have come across a
number of people grumbling about the fluctuating pressure on their boiler. This
increase and decrease in the pressure of your boiler can probably be an outcome
of a number of reasons which we have explained below along with the solution as
in how to fix the pressure of a combi boiler.
What is a Combi Boiler?
A Combination boiler is
a native space saving idea that serves you with a high efficiency water heater
and a central heating in a single compact unit that operates to heat the water
directly from the mains in order to cut down the installation of a hot water
storage cylinder or the cold water storage tank in the loft.
What should be the pressure of my
The pressure of your
boiler that can be viewed on the pressure gauge located on the system should have
its needle pointing between the 1 and 2 bar as the correct amount of pressure.
While some of the pressure gauges come with 2 needles, with the red needle
serving as the marker and the black one showing the actual pressure. In that
case, if your boiler is at the right pressure, then both the needles should be
pointing at the same number. A number of other boilers have an LCD display to
present water pressure in the system.
Why is my boiler pressure high?
The heated water
expands as soon as the boiler begins to heat and causes the pressure gauge to
increase. This is basically why the pressure of your boiler increases. Though
the modern boiler systems comes with an in built pressure relief valve that is
installed in order to control the quick leaps in the pressure, but in most of
the cases a high pressure boiler puts unnecessary strain on the system, which
eventually results in the breakdown of the unit.
How to lower the boiler pressure?
- Check that the pressure relief valve is tightly
closed- Re-pressurizing the
boiler would require you to turn the valve or filling loop to pump water into
the boiler and this might be easy to forget.
- Bleed your radiators- Keep bleeding the radiators to reduce the pressure
in the central heating system and continue the process until the boiler
pressure being read on the display has restored back to the safe levels.
- In case of the
boiler pressure still persisting to be too high, the reason could either be the
fault with the filling loop or you need to re-pressurize the expansion vessel.
Though the pressure still might be irregular, the pressure relief valve would
prevent the boiler from over pressurizing the system in order to help it from
breaking down and carry on as usual as long as you are not experiencing loud,
Why is my boiler pressure low?
The most common reasons
for a Combi boiler loosing pressure might be an outcome of a leakage in the
pressure relief valve, an issue in the expansion vessel, air in your system, or
a leak in the heating pipework itself. So in case the boiler pressure falls
below 1 you would need to top up your system. While the steps to do this would
surely part their ways depending upon the specific boiler models, we would
highly recommend you to consult your boiler’s instructions.
How to increase the boiler
In case of your boiler
pressure being too low you need to top up the system that can generally be done
in the following ways:-
- Initially, you
need to turn off the boiler and wait for the system to cool, before making any
- Operate the system using a filling
link or loop- While this can be done
in 3 ways :-
- External- For
this you would need to attach the filling loop to the corresponding valves and
slowly move the lever. The process needs to
be continued until the pressure needle moves into the green zone.
Disconnect the external filling loop once you are done.
- Keyed filling
link- For this you need to insert the internal filling key into the loop and
twist it until it gets closed. Turn the nearby knob in order to allow the water
to fill into the heating system. Continue the process until the pressure needle
falls into the green zone. Once yo.u are done turn the knob back to its
original position and remove the key.
- Keyless filling
link- this is one of the easiest methods in which you simply have to move the
filling lever until you hear the water entering the heating system. The lever
needs to be kept lifted until the pressure needle moves into the green zone and
then be released.
- Turn on the
boiler in order to check if the pressure holds.
- In case you
still find the pressure to be below the recommended limit then the problem
might be with the gauge or the heating system. For this you would need to call
a heating engineer in order to inspect and service your central heating system
Recommendation– If in case the results are found to be same even
after the operation of the above mentioned techniques, please consult you heat
exchanger as soon as possible.