First of all, I'm no water expert. I use filtered boiled tap water (it's a small filter costing about $20, not the expensive one). I live in a new building, and the water pipe is in good condition. If the water pipe is rusty, you may need an advanced filter. I prefer boiled tap water to distilled water and mineral water because distilled water lacks minerals vital to our body, and the minerals found in mineral water varies from source to source, and great amount of minerals are not suitable for babies. In fact, some mineral waters which claim to be all natural are discovered containing harmful chemicals, the most recent one being Volvic. There are several other threads about distilled and mineral water, and you may use the search engine of this forum to have a look.