Valiant Boiler Heat exchanger blocked

[snb]

The exchangers on the Vaillant 618 can be poweflushed, however if it has any tubes that are badly blocked then it won’t be able to shift them. But on most cases we are successful at flushing them

 

[Miller4]

I have a digital water testing meter used for window cleaners to check purity of water, would that be ok to test water ? I was going to put DS40-system cleaner in to help clear Rads/system out before any further work is carried out I have 19 Rads in total but don't know if I would need more than 1 pack. Boiler Valiant 418 EcoTec Plus not 418 as I stated with a Gledhill Hot water storage tank and cold water header built in as 1 tank and 2 central heating type pumps fitted to hot water storage system.

 

[Razor900]

I don't think you can really successfully flush a thermal store actually.

They're called sludgebuckets for a reason!

Personally I think I'd keep the Bunny and spend the money on a conversion to an unvented or similar if possible.....