I just use filtered water from my fridge or from my Brita. Haven't noticed any nasty build up in the humidifier or any hazy production. The larger Honeywell I u

I just use filtered water from my fridge or from my Brita. Haven't noticed any nasty build up in the humidifier or any hazy production. The larger Honeywell I use in the master bedroom is the top fill which is designed as filter free.