Returned from holiday to find TWO of my Geberit concealed cisterns leaking, for quite some time, behind the scenes, judging by the damage! Geberit blame lack of bracing clamp so seal compromised when the loo's were pushed into place - same as poster here, not enough space before elbow to attach the brace (got 3 altogether & all different fitters, none have brace). Gave distinct impression 2 new cisterns required so have started searching for suitable plumber - this thread has saved me hundreds of pounds £££ EXACTLY the same problem, & have ordered clip & washer for less than £4, though will get plumber to remove toilets (other repairs needed to build in cupboards, floors etc). Thanks everyone.