[Al Skierkiewicz]

De-ionized water (sometimes referred to as "distilled" by users) is used for cooling water in some high power transmitters. Water flows over high voltage and low voltage parts and current probes are used to determine the conductivity of the water. High voltage power supply trips at a few milliamps are common with poorly maintained equipment. In some cases, designers actually use china pipes to keep the water insulated from sensitive (read 'human') objects just in case some contamination enters the system and causes conduction to skyrocket. The UHF transmitter I worked on in Peoria many years ago had 25,000 volts across the output tubes and the cooling water. As I remember it had both a ceramic filter and a de-ionizer in the circulating water. The collector (plate/anode) was vapor cooled. This means that cold water is just poured onto the structure and cools while turning to steam vapor. The steam is carried off to a heat exchanger where it is turned back into water. Regular maintenance includes scheduled water changes.