hi guys - i have a grohe adagio concealed flush fitted and water pressure is mains fed - there is a restrictor in it but takes ages to refill so i removed the restrictor and it fills really quick but right at the end of the fill there is a slam /thump in the cistern - is there any way to stop this slam/thump noise or will i have to put the restrictor back in and just persevere with the slow fill -- thanks for any advice