Evacuated tubes do not have an industry standard “degradation” value – however it is estimated that the tubes may lose approximately 0.5% output per annum. Apricus tubes are tested to the most stringent of standards, and have a barium coating to absorb any impurities that may occur over time within the tubes vacuum. Apricus heat pipes are manufactured from high purity, oxygen free copper to ensure the longevity of the vacuum. The tubes are covered by a 15 year warranty that they won’ t lose their vacuum, and if the vacuum is compromised within the evacuated tubes – they turn white as an indicator