I intend to fit a resin ion exchange type water softener into my water 
supply which will leave a residue of salt ions in the water.
I have no problems with my hot and cold water system, the advantages are 
clear to see there, and I know about the need for a 3rd tap in the kitchen 
for drinking water.
My question relates to my heating system, which is an enclosed type with 
header tank and traditional copper heating cylinder and old Vulcan free 
standing boiler with cast iron heat exchanger, and radiators. I can't make 
my mind up if there are overall benefits in installing the softener such 
that it fills the header tank with soft water too.
The trace sodium levels may accelerate corrosion in the radiators and 
boiler, however does the corrosion inhibitor does as it says with all types 
of feed water, whether this be trace sodium levels or not?... I see the 
benefits in not having scale forming salts building up in the radiators, 
pipework and boiler, where kettling has not yet been a problem, but if I 
upgrade to wall hung boiler may become a problem.
Any arguments both for and against please...and moreover anyone with 
experience of doing this having negative effects?

Like yourself, I can see both sides of this one.
However little you drain and fill a system, you'll always get a build up of 
scale and if it's a low water content boiler this will probably show up 
sooner. I think that I would have the header tank fill with soft water 
together with an inhibitor. The most important thing is that if the system 
has been properly designed then you shouldn't have any air being introduced 
into it and it's that which causes the corrosion. No oxygen, no corrosion.. 
Even though there are trace sodium levels present with artificially softened 
water, I wouldn't like to guess whether or not it would worsen corrosion. 
What I do know is that you shouldn't drink it, as I installed one some years 
ago when my some was only a few months old. In those days they didn't advise 
on fitting a separate drinking tap and this caused him severe constipation. 
Fortunately, it didn't do any lasting damage.
"biggirlsblouse"  wrote in message 
news:CgrLe.6430$QU4.4045@newsfe5-win.ntli.net...

>I intend to fit a resin ion exchange type water softener into my water 
>supply which will leave a residue of salt ions in the water.
> I have no problems with my hot and cold water system, the advantages are 
> clear to see there, and I know about the need for a 3rd tap in the kitchen 
> for drinking water.
> My question relates to my heating system, which is an enclosed type with 
> header tank and traditional copper heating cylinder and old Vulcan free 
> standing boiler with cast iron heat exchanger, and radiators. I can't make 
> my mind up if there are overall benefits in installing the softener such 
> that it fills the header tank with soft water too.
> The trace sodium levels may accelerate corrosion in the radiators and 
> boiler, however does the corrosion inhibitor does as it says with all 
> types of feed water, whether this be trace sodium levels or not?... I see 
> the benefits in not having scale forming salts building up in the 
> radiators, pipework and boiler, where kettling has not yet been a problem, 
> but if I upgrade to wall hung boiler may become a problem.
> Any arguments both for and against please...and moreover anyone with 
> experience of doing this having negative effects?
>