Some buildings were originally installed with toilets that made use of subterranean or stream water and owners of these buildings found it extremely difficult to change to seawater because substantial changes were required to the existing plumbing and other ancillary structures . these modifications were expensive therefore owners did not accept them 至于原来已设有利用地下水或山坑水作排污用途的建筑物，除需将原有冲水设施改装外，输送海水的管道及其他配套设施，均较一般使用淡水或山坑水的管道昂贵，故多不为业主接受。
