I had my conventional system converted to a sealed pressurized system
with a pressurized HW cylinder, and now I find I have a small leak.
Basically I lost the boiler, cylinder and 2 loft tanks, and gained a
Vokera Mynute 16e system boiler and Indesit 150STI HW cylinder.
I kept the rads and flow and return pipework, and obviously these are
prime candidates for the new leak.
My house is 3 storey, with the new boiler and cylinder in the loft
(which is floor 3, assuming ground floor is floor 1 - just to be
The only radiators that seem to require bleeding are on floor 2 (the
middle floor!) and these are toward the back of the house. There are
other radiators on the middle floor which never require bleeding.
I would have thought that if air congregated anywhere it would be at
the top of the house, but this doesn't seem to be the case.
Does this situation say anything about where the leak may be?
Kind regards, Dave
davejepson @ gr a ff TAKE_ME_OUT iti.net
I didn't have a leak before I installed the new system. I can only
strongly suspect I have a leak because of the regular bleeding I have
to do. Also, as noted elsewhere in this group, and given the nature of
my upgrade (now I have pressure in my old pipes and rads) a leak is
I cannot see water leaking anywhere no. As a _very_ rough guide to the
size of the leak I have to bleed a 40x40cm single radiator every week.
What seems peculiar to me is that I only have to bleed 3 radiators at
the back of the house on the middle floor. I just wondered if that
said anything about the location of any leak, or if its a red herring.
Kind regards, Dave
Once air is in, it gets carried to where velocity is low and there is a
local high spot. I needed to do weird things with balance valves and
pump speeds to get all my air out...and it ended up in the furthest
point of the house at a local set of high spots.
I think you have outgassing, not a leak.
In answer to this and the other questions about changes in pressure:
Since having the system installed (18th Oct - 2 months now) I have
only bled one of more of the group of 3 rads. At the time I was not
knowledgeable enough about this system to realize that by only
bleeding and not filling I was reducing sealed system pressure.
This came to a head 2 days ago - i bled all 3 in the morning before
work - quite a lot of air came out - estimate a 80x40cm rad-full. When
I came home the house was cold. I introduced water using the filling
loop, and the boiler sprang back to life.
I filled to an indicated 1.5bar, the system being cold at this point.
I then spent the rest of the evening watching the pressure. When it
got to 2.2bar I bled some of the rads and reduced it to 1.9bar. I
don't know if this was the right thing to do.
To be honest I haven't really been observing the pressure changes thru
the last 2 months. I will now and I'll post further observations as I
make them. To Natural Philosopher - I take your experience on board -
the situation may right itself over time.
To the question above, what does this rising pressure situation
My plumber used a Fernox inhibitor so I hope that more or less rules
Thanks for all the responses by the way - its nice to meet a
knowledgeable crowd willing to help others learn.
Kind regards, Dave
The system should be designed to limit any pressure rise to 1 bar, although
typically, a system will rise by less. The "standard" (if such a thing
exists) is to design for 1 bar cold and around 1.5 bar hot. The pressure
rise is determined by the size of the expansion vessel. This is frequently
part of the boiler. However, if the system is large, then an additional one
may be required, as the boiler one is just a compromise to be small enough
to fit inside, but large enough to work for most systems.
Normally, to fill, wait for it to be cold and adjust to 1 bar. If your house
has more than 3 floors, tell us how many and on what floor the pressure
gauge and boiler is, as the correct setting may need to be more carefully
Not so in my case. I havbe a pop off valve, but have run the thing at
around 2.5 bar, slowly falling over time as things settled down.
The OPs story is VEY similar to mine, except I have not bothered with
inhibitor yet. I think the flux residues and so on in the pipes cause
gas generation, and my system too would show a rise in pressure when
hot, and then obviously drop dramatically after bleeding, and need a new
top up. Maybe also trapped air slowly gets 'swept up' - it took me a
long time to get it all out for sure. I had to run the pump at max speed
and close off various branches to get everything bled properly.
There may be no leak. If its a sealed system, you cannot get air IN
except by re-pressuirsing and carrying it in, in teh mains.
My pressurized system took about 6 months of slowly klless and less
bleeding before all teh new piperwork and new mains water stopped
gassing. I had to re pressurzie every few dyas at first, then every
week, then every month, and now I haven't done it for a year.
Just keep bleeding and repressuirizing. It goes eventually.
Prostate trouble ?
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
I'm not at all sure why women like men. We're argumentative, childish,
unsociable and extremely unappealing naked. I'm quite grateful they do though.
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