Blockages in urinals are caused by the build-up of scale in the urinal traps, drains or waste pipe work. This is produced by the deposition of dissolved salts that are present either alone in the water supply such as limescale or in combination with uric scale and salts.
 
Harsh chemicals and drain un-blockers are an easy way to unblock the urinals and pipework, however these can be detrimental to the environment and are only a short term solution to a long term problem.