Unhappy client

Pls guys if u have an ariston or heat tech geyser pls ensure you have it installed as per the diagram I bought a geyser in 2019 and recently the geyser started to leak called heat tech as I still have a warranty and they refuse to replace the geyser due to it not being installed according to the diagram I would have never known that and I had a plumber install the geyser so I wud not have known to go back n tell him it's not installed according to the diagram had no issues after installation and they geyser worked well until this week wen heat tech sent their plumber I was told warranty is voided because the geyser was not installed according to the diagram how was I suppose to know that and now they refuse to repair or replace which I think is so unfair