The water dispenser may also be cleaned with disinfectant alcohol or it can only be used with hydrogen peroxide 8%. To how much time should this happen?

In   "Practical Pharmaceutics" (KNMP, 2015), they set in   "chapter 27.5.2.9 Chemical Disinfection" to flush the installation (if the fittings and the taps allow) with hydrogen peroxide ( Technical quality) or peracetic acid, both at a concentration of 8-10% (% by weight for hydrogen peroxide, no volume%). Afterwards it should be well washed. The contact time is not spoken. They speak only about "flushed". Personally, I think that if you leave the stock holder overnight filled with the solution, it is sufficient. It should be washed sufficiently and this can be best with hot tap water to end with purified water. Hot tap water is also germicidal and decomposes the hydrogen peroxide.  

on the frequency I could not find a clear guideline. It depends on a lot how regularly the bottle is empty and filled with freshly purified water. Use of large volume bottles, which are slowly emptied, should be avoided. If the bottle Is empty every week, I would say that a disinfection can be carried out at least 6 weeks.   You can install the Burette on the bottle and fill it internally with the solution in the bottle. Of course the Burette must also be well washed.   about alcohol disinfection is not spoken. A serious problem, which can occur, is the formation of a biofilm on the glass wall of the bottle. Biofimen are difficult to remove and therefore we prefer a slightly more aggressive chemical product such as hydrogen peroxide or peracetic acid. The glass wall of the bottle should remain nicely clear transparent.