Sorry to hijack your post but my Ideal Istor is doing the same thing-ish
But it only does it when the DHW starts, on central heating it's fine, it's only as the Valve changes from Central Heating to DHW replenishment it makes a REALLY Loud bang, and all the heating pipes and boiler shudder.
It also loses presure on the heating system after it's done it, as if the heating system water is entering the DHW system as there is NO leaks and theres no escape from the discharge.
But it only does it when the DHW starts, on central heating it's fine, it's only as the Valve changes from Central Heating to DHW replenishment it makes a REALLY Loud bang, and all the heating pipes and boiler shudder.
It also loses presure on the heating system after it's done it, as if the heating system water is entering the DHW system as there is NO leaks and theres no escape from the discharge.
