On Tue, 7 Nov 2017 11:29:53 +0000, Martin Brown
wrote:

On 07/11/2017 10:29, AnthonyL wrote:


A couple sputter, water comes out but with a sputtering sound and/or a
whistling sound and this is where I'm confused. It seems no matter
how much I let out (I'm talking cup fulls not gallons) they still seem
to sputter. They sputtered yesterday, today and I expect they will
tomorrow.

Usually you find that any air in a system will mostly gravitate to one
or perhaps two radiators that are the highest in the system. The tops
will be noticeably cooler when the rest of it is hot if air is there.


I'm not sensing much difference. My old house had a top up tank, an
upper (bathroom) radiator often needed bleeding and it was obviously
cold on top and air (and just air) would come out until water came
out.

If there is a lot of air in a poorly designed system after refilling
then you will hear it bubbling up in any vertical pipe runs and a change
in pump noise when there is air going through it.

Is this air in the system or is it just the shape of the screw?

If it sputters it is probably from gasses in the system.

Am I correct in assuming that air cannot be introduced into the system
unless there is serious corrosion or the like going on?

Only if you bleed it with the pump not running. If you try to bleed with
the CH pump running all bets are off. It can sometimes suck air in.


I turn the whole boiler (CH and HW) to Off before starting.

How much oxygen am I reintroducing repressurising the system?

Worst case not a great deal. And perhaps none at all if the repressuring
is done by a piston with the air in a bladder which is how the one I
have to sort out from time to time seems to be engineered.

It might be worth adding a corrosion inhibitor if it is a new
installation (elderly systems can react badly to any kind of change).


It's an elderly system (like me). Never had any problems with my coal
fired back boiler CH system in 30yrs apart from the occasional bleed
of the bathrooom radiator mentioned and that was a two storey house
compared to this bungalow.

--
AnthonyL