This is something I cannot stress enough - DO NOT USE TAP WATER WITH YOUR CIGARS!
The use of tap water in your humidor or any form of cigar storage is simply a death sentence for your precious cigar collection.
Not to sound like a negative-nanny, its just not worth the risk - distilled water is cheap; Boveda 2-way humidification packs are cheap - in fact most proper humidification systems are always a lot cheaper than the value of your precious cigar collections.
Tap water is without a doubt the quickest way to ruin a cigar collection...
What can tap water do to my cigar collection?
Some people say it is okay, but the cold hard reality is municipal tap water contains all sorts of crap (bacteria and sediment) that doesn't bother you when washing with it or even drinking it; but when your using a cigar credo device (the device with florists oasis block in it) or similar humidity devices; the bacteria and sediment build up and will ultimately create a breeding ground for mould that will destroy your cigars.
These microorganisms will also imbed themselves into the Spanish cedar lining of your humidor over time. It won't happen over time, but it will happen...
Mouldy Cigars
Sadly, once you spot mould on your cigars there's very little you can do; if you can see it - then there is a very high chance it is also throughout the internals of that cigar as well.
If you are lucky, maybe just one or two cigars will show the signs and you can "chance it" and isolate the rest and try to save them - but remember that mould is for the most part not visible to the eye until its too late.
Mould is also toxic, so that is largely why it is recommended any mouldy cigars should simply be discarded and fast.
You could try freezing the remaining cigars, but it is not entirely clear if that will kill off or simply hibernate the potential mould within them.
Can I save my humidor?
There a couple of techniques you can undertake, but there is no guarantee that this will be 100% in the eradication of mould in your humidor (sadly).
Firstly wiping the humidor out with Rubbing Alcohol is the first step in sanitizing your humidor.
Secondly gently sanding out any mould patches/marks is required (with very fine sandpaper); then vacuum the humidor out and then repeat wiping it out with Rubbing Alcohol.
Hopefully this works, you'd want to repeat the Rubbing Alcohol for a couple of days just to be safe and then re-season your humidor using PG Solution (again, NOT tap water).
Then leave the humidor for a few weeks and see if anything grows... maybe sacrifice a crappy cigar or two just to see...
Why you shouldn't use Cigar Credo device or similar humidification products?
Cigar credo's contain these florists foam blocks or oasis blocks as they're also known - which is why they're commonly called Cigar Oasis's but shouldn't be confused with the humidity systems from Cigar Oasis (even though they use these or gel-beads).
Basically these blocks are the perfect trap for tap water; of course if you only use PG Solution or distilled water, then you have pretty much nothing to worry about.
Ultimately though the problem is these devices are One Way Humidity Systems - they pump out humidity, but cannot re-absorb it; they don't have any means to regulate how much humidity they produce.
This is why we always recommend using Boveda's 2-Way Humidity System; as they will at least re-absorb excess humidity and keep your cigars as close to perfect as you can get.
Why is Distilled Water and Propylene Glycol recommended?
Firstly Distilled Water should be just that, water that has been distilled and the impurities removed - making it safe to use with your cigar collections.
Now, here is where people can get unstuck - you need to use PG Solution (a 50/50 mix of Propylene Glycol and Distilled Water) to Season your humidor and you are supposed to use it to top-up your credo devices (however after a while just using distilled water will work too).
Why? You need the "stickiness" of the Propylene Glycol so retard the evaporation of the distilled water; without the PG Solution and just using distilled water, it will just evaporate very quickly in your credo and likewise if you just used distilled water to season your humidor.
You will basically be chasing your tail constantly if you don't use PG Solution.
Remember - if you run out of either, its better to let you humidity to drop temporarily then to resort to using tap water!
What is the best way to humidify my cigar collection?
Well, I've said it already and I'll say it again - short of buying a Raching fully electronic humidor; your best bet is Boveda's 2-Way Humidity System!
Again (sorry to sound like a stuck record) they are the only system that has the ability to re-absorb humidity when the relative humidity changes too much (generally due to weather).
The Raching and other humidors like it use electronics to monitor humidity and obviously stop producing humidity when they hit their level and because they control the internal temperature, they don't tend to have fluctuations.
The Cigar Oasis systems also use electronics to cut off humidity production. They are often used when people convert old wine fridges etc. into a humidor - but they also have pitfalls but that's a story for another day sorry.
How do I season or re-season my humidor?
We have an existing BLOG post on this subject, please refer to it here.