My son has just moved into a flat which has a boiler which I presume
from his reports is a combi - no storage tank AFAIAA. There is a
pressure gauge which is currently reading well into the red. Apparently
the heating and probably the hot water are switched off. Is this a
problem, how could he release some pressure if necessary and is there
any danger in turning it all on? Sorry if these are basic questions but
I have only ever had stored water systems myself. TIA.
Hi Peter, if the flat has been empty for a while (the college / Uni Xmas
break, for instance), it's more likely the red's at the low pressure end
(showing less than 1 bar or so) - if so, neither heat nor water should be
used until it's repressurised - the hot water might work anyway, though.
Under the boiler there'll be a pipe from the rising main with a fill valve
(similar to an isolator valve, with an open threaded end and either a
screw-slot or a lever) and a filling loop (a flexible pipe with a matching
threaded end) connected to a one-way valve into the heating circuit - at
least the filling loop's open end *shouldn't*be connected if the water reg's
are being followed, usually they are as they're often in an inaccessible
To correct the pressure, attach the filling loop to the fill valve (fairly
tightly) and open the fill valve, observing the reading on the gauge and
closing the valve once it's somewhere in the middle. Your son may need to
repeat this procedure once the heating's running if he notices cold tops to
the radiators and has to bleed the air out to get them working properly.
To bleed the radiators he'll need a radiator bleed key (surprise!) from the
DIY shed, a couple of quid, to open the bleed valve at one end of the top of
the radiator a couple of turns until he can hear air hissing from the valve,
and a rag to catch the drips and/or spray of filthy radiator water before it
gets on the landlord's carpet / wallpaper / curtains - close the bleed valve
once water flows. Once the radiators are bled, check the gauge reading, top
up if required, repeat the procedure if (when) the pressure drops again.
Hope that helps,
(The engineer formerly known as Homeless)
Bleed a radiator or let the pressure relief valve take care of it.
The only problem in having the heating or hot water 'switched off' is that
you won't get any heating or hot water ;-) Oh and a severe frost may make
your pipes holey.
Depends what you mean by switched off. - boiler off electrically, room
thermostat too low, airlock in boiler, bolier DHW thermostat off or too low,
same for heating.....
Probably best to relieve the pressure. Easiest way is if there are any
draining points anywhere on the central heating (normally by radiators
and/or at the lowest point on the system - just unscrew the valve on the
drain point and drain off enough to bring the pressure down to the
green or blue zone. Shouldn't need much liquid removing at all; if the
pressure doesn't fall, this might mean that the central heating is
hooked up to the water main and the valve is open (ie the CH is at mains
pressure). In that case, you'd need to locate the filling loop (usually
a braided steel hose below the boiler) and turn off the valve at the end.
If there's no drain points there ought to be one within the boiler, or
he could loosen off a pipe feeding a radiator slightly - however that's
potentially messy - high risk of black sludge on the carpet!
Once he's brought the pressure down, the next thing is to find out
whether it stays stable when the system is switched on, or goes up
again... that's another (different) question!
Well depends on the boiler there is many ways, Firstly why is the
gauge in the red? is the filling loop still open or passing or did you
over fill it?
Well back to your question about releasing the pressure it is
proberbly best to put a hose on a drain point and release it that way
or let it out a bleed valve on a rad, This will take a while and can
be a little awkward to do .hope this will give you a start
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.