Diluted vs cask strength

They use water. You can dilute it yourself and wait a few days for the flavors to stabilize. https://www.distilling-spirits.com/tools/calculations/diluting-alcohol/ There was a case study about this topic: https://onlinelibrary.wiley.com/doi/10.1002/fsn3.629 You need to read point 2.1 (2.1 Sample Selection), 2.4 and 3.1 (Effect of dilution on sensory profiles) and 4 (Result). "For the R1 dilution series, R1 was significantly different from R1‐E for all attributes, having higher intensities for all attributes except silky mouthfeel (Table 4)". "For the R2 dilution series, all attributes were rated higher in R2 compared with R2‐W and R2‐E (Table 6)." The study says that when you dilute the rum, the intensity of the flavors is also decreased but they are still there. You can improve the mouthfeel with the dilution if you are not used to high proof alcohol. Lots of whiskeys are diluted to lower abv. However I think that the best drinking abv for rum is 55-57%. I enjoy the intensity of flavors and my palet is used to high proof alcohol. Everyone has to decide for themselves how they enjoy the rum. If the alcohol bothers you, there is nothing wrong with reducing it. However, one must be aware that the intensity of the aromas changes. "Some people insist that a small splash of water is needed to open up the flavor. Still others state that distilled spirits need to be diluted to ~23% ABV to get the best flavor perception of the beverage. This has been the traditional practice in the whiskey industry for years, and a common reason given for this practice is to reduce the pungency of the alcohol (Smith & Roskrow, 2012)."

Thanks a lot, gotta read in.

Simply put, it's always better to buy stronger proof version of the rum, and dilute it yourself before drinking, because the aromatics are forced out of the solution at the moment of dilution, and you will have a stronger and more enjoyable experience drinking. Moreover, since most aromatic compounds are bound to the alcohol, not water, high proof rums will bring more flavor and aroma to your cocktails and cooked meals (should you decide to use rum for cooking). Since alcohol slowly evaporates over time, overproof rums also last longer before losing flavor and aroma.

Do you recommend any kind of water? Where I live tap water sucks and I filter out but can also use mineral water.

I recommend distilled water / demineralised water or real soft spring water. Otherwise, your drink will be murky, because of lime and minerals. Sometimes you recognise it in a bottle as little flakes.

I live in Prague, Czech Republic, and we have quite hard (=lots of minerals) tap water, but it was never a problem. I regularly use cold tap water to dilute my rum, and never ever did I observe the result murky (you only use a few drops anyway, or a teaspoon). Distillers often go on singing serenades about "quality, pristine, natural spring water", but I have read some insider articles, and as long as the water has no distinct smell or taste, anything goes. Compared to the strength of what come diluted in the alcohol, it won't be probably recognizable anyway. When you have "flakes" in your rum, it might be: - pieces of cork. I once bought a bottle from Companies des Indes, and they probably used a cork with incorrect binder, and the cork particles became unbound and dispersed into the liquid. The seller was kind enough to replace the bottle. - crystalized additives when the producer goes too crazy - sugar, glycerol, various dry fruit extracts or other chemicals may "manifest" out of the "clean" spirit. - various contaminants that got into the bottle while it was opened

So I did a tasting of pure water in rum glasses, comparing tap, filtered and mineral (bottled). The differences are huge both in aroma and taste. I think i will use bottled water with low minerals to dillute rums.

@Rene Rum Well, I must say I have never thought about diluting a whole bottle - because once you overdilute, there is no way back, and because overproof rum lasts longer, ethanol is its own preservative, and because in the moment of dilution, the aromatic compound forced out of the alcoholic solution amplify the scent of the rum - and you don't want to lose that moment. That's why absinthe is sold and stored overproof, and diluted just before consumption.