The inside surfaces of white tanks must be kept permanently free for inspection purposes and to carry out any waterproofing which becomes necessary. Should they only be accessible by dismantling replacement parts, equipment and so on, this must be capable of being done with operations on the run. If access cannot be assured in the area of floor slabs under machinery and so on, structural design measures must be taken to ensure that, if any water does penetrate, it cannot cause damage and can be run off as designed. Wall claddings on the inside of WU structures (liners and tiles) are not allowed.