I have a triton opal 9.5kw shower. I use it on the lowest temperature setting (the dial will only go as low as 4 on the high button setting) but water is scalding hot. When I use the lower button setting(1red line) the water is cold and if I turn the temperature round to number 10 hardly any water comes out - just a trickle. I bought the shower 3 years ago but only had it installed a few months ago. Can anyone advise please