Dental units (1) include the testing stand (4) that supports from inlet point (12) to instrument (14) of water loop (13) supply drinkable water, including resist that be stuck in the anti-stagnant systems of thatsaid systemcharacterized include that valve (16) is disposed along water loop (13) delivery instrument (14) (4) Valve described in testing stand is to open or close, according to auto-programming (30) and/or manually (31) When open, it, which guides water, leads to dental units drain electrode (18) from circuit (13) to anti-stagnation discharge pipe (17a or 17b).
