Miele Novotronic w827, inlet pressure problem?

Hi, I´ve just gotten a miele novotronic w827, unfortunately I´ve got not much pressure at home, I fitted a small water tank on top of it (diy style) but still it seems to not have enough pressure.
Besides, it seems now that the washing machine doesn´t stop the water from coming in, this must be because I have opened the the inlet valve to have a look, although I fitted everything back as it was. Any solutions or advices?
thanks a lot!
Diego