Sealed system~ A) heat exchanger rot. B) pro & cons

[mrlapou]

Have had the 4th engineer quoting for a replacment condensing Grant boiler.
The chap who came round last night was the first to raise the issue of heat exchanger rot.
He said, if softened water (from a normal dometic softner) in conjunction with inhibitor is used, the solution is slightly acidic, which will rot the boiler's heat exchanger very quickly. Is this true?

He suggested a sealed system (i.e. with pressure/expansion vessel) which has tank sited in the boiler housing, filled by a hose connected to normal mains tap water. I'm happy to consider this but am concerned about the additional pressure in the heating pipework and rads. What are pros and cons of this type of system?
What sort of pressure will be in the system pipework/rads?
How is any acumulating gas drained from the rads?

 

[BigBurner]

Have had the 4th engineer quoting for a replacment condensing Grant boiler.
The chap who came round last night was the first to raise the issue of heat exchanger rot.
He said, if softened water (from a normal dometic softner) in conjunction with inhibitor is used, the solution is slightly acidic, which will rot the boiler's heat exchanger very quickly. Is this true?

He suggested a sealed system (i.e. with pressure/expansion vessel) which has tank sited in the boiler housing, filled by a hose connected to normal mains tap water. I'm happy to consider this but am concerned about the additional pressure in the heating pipework and rads. What are pros and cons of this type of system?
What sort of pressure will be in the system pipework/rads?
How is any acumulating gas drained from the rads?

There is element of truth in what the man says. Have the F&E tank taken directly off the mains pipe by-passing the softener.

 

[gas4you]

You only have to worry about softened water in boiler HE if the HE is aluminimum.

Th steel rads wouldn't like it either, but he has not mentioned that.