Hi, i am new here so please bear with me, the drainage on my shower waste has blocked,i have tried one shot chemicle cleaner but still no good,i have tried using a plunger which did push a little water away before stopping again. i have tried connecting the garden hose inserted into the head of the rubber plunger and when i hold this tightly over the shower drainage hole the water flows through when under pressure, but will not drain when not under pressure, any ideas anyone please.