Many ground mounted luminaires are fitted with a specially designed Anti-Syphon system to reduce the likelihood of water entering the fixture through the cable. Where the Anti-Syphon is not fitted as standard, it can be specified in some instances as an option. This system is designed to counter the problem of wicking (siphoning) of water through the supply cable into the lamp housing, causing water to condense and dramatically shorten the life of the lamp, lamp holder and luminaire. Siphoning is caused by the expansion and contraction of air inside the luminaire due to heat generated by the lamp. As the lamp heats up, the air expands and is forced down into the supply cable. The problem manifests itself when the fixture enters the cooling cycle and the air cools to create considerable suction inside the lamp housing and supply cables. The joint between the luminaire cable and the cable from the transformer becomes critical at this stage because a leaking or poor cable joint will allow water to be siphoned up the cable directly into the luminaire. Unless this cycle is broken this action will dramatically reduce the life of the luminaire.