Originally Posted by Tom Kershaw
Sorry can not give an exact amount, this is because I use it for drinking water as well as mixing WS developers particularly Pyrocat-HD. Because as I posted earlier, of a white precipitate through just using tap water. This wouldn't have particularlly bothered me but when the film dried there was streaks of white 'film' on the upper surface which fortunately was easily removed with a soft cotton cloth. However since I've started using the Brita this has not reoccured.
I've never had problems with WS PMK pyro with ordinary tap water; filtered just to remove the larger particles (Paterson tap filter).
With regard to the deioniser, again I don't monitor the exact amount, because it's a colour change resin, goes from brown to red when it needs replacing. However the manufacturer states that its capacity is from 40 to 160 litres depending on water hardness. I now only use it to mix stock solutions of film developers and toners.
As Photo Engineer said, the general use of deionised water could well be overkill.