An efficient wash up routine will remove milk residues and bacteria from the plant. This will maintain milk quality, improve the appearance of the parlour and prolong the life of milking equipment. If problems occur with the wash-up routine, then milk films will build up in the plant. These films provide nutrients for bacteria which can then multiply and increase the TBC or Bactoscan. Some plants are fitted with air injectors that admit "slugs" of air to increase the turbulence of water all around the pipes. Air injectors are of increasing importance in large bore systems so that the entire surface of each line can be physically cleaned.