If L _ _ _ away doesnt remove the marks then try the DARK blue L _ _ _ l bowl cleaner ( get as much water out of the bowl as you can first so it can sit on the marks for a while, ive had good results with both products removing MAR type marks BUT your LL is not obligated to replace the toilet until it no longer works at all ( or something like say a earth quake makes the bowl break say at the bolts .