Geyser element replaced a second time in 3 weeks, paid in full and no warrenty.

<p>Millennium Plumbers replace a geyser element and do not advise me to put in a non-return valve.</p> <p> </p> <p>1.       On the 21st August 2016 the geyser element and thermostat were replaced by Millennioum  plumbers after informing me that the element had burned.</p> <p>2.       On the 15th September 2016 I call them again to replace the element again for the same geyser. I was under the impression that there work was guaranteed for 3 months, but they made me pay again. The reason they gave was that the geyser run empty and it could be because of the City Council water flow (How do you proof this?). They then suggested to installed a non-return valve, that I agreed too.</p> <p> </p> <p>I asked them why did they not installed the non-return valve when they replace the element the first time as this would have prevented the element from burning out and it would not have been necessary to replace it after 3 weeks for the second time. They just said the following " it is not a requirement to install a nun return valve s. I also feel that as professional plumbers they should have advise me from the start to install a non-return valve, as I have not climb into the ceiling and was not aware that there are not a return valve installed. I have tried to reason with the plumbers manager without success.</p>