Is any tap water safe to drink in Japan?

I don't feel like carrying a big bottle of water from my hotel everyday. Is tap water safe to drink anywhere, anytime when I need it ?
It will save me some money too.

This same question has popped up here many times before. Please try to do a basic search yourself before asking for help.

http://www.japan-guide.com/forum/quereadisplay.html?0+94994
http://www.japan-guide.com/forum/quereadisplay.html?1+4131
http://www.japan-guide.com/forum/quereadisplay.html?0+57179

You can buy bottled water from vending machines and convenience stores, which are everywhere in Japan. Also, you get free water served in restaurants.

Tap water is safe to drink in japanese houses. But, tap water in hotels is not guaranteed. In each hotel, clean guaranteed tap water is temporarily reserved in a tank, then pumped to each room. Water in a tank is not guaranteed by water supplier(city officals). tank' and pipes cleaness is responsible for building owners. I am a japanese. I do not drink hotel tap water.
Even if hotel water is not guaranteed, but good enough to drink. Hotel's always fresh tap water is much cleaner and safer than bottled water storaged at room temp.

Is tap water safe to drink anywhere,

Yes

anytime when I need it ?

Water fountains are fairly common around public parks and toilets. Otherwise you may have trouble finding free water.

Not sure what the above poster means about hotel water being safer/cleaner than bottled, but they do have a good point that you'll occasionally run into places that don't recommend that you drink the water. That is common on trains, public lavatories, etc. and it is usually clearly marked at the tap. Btw, in the few times I've come across this situation at a hotel they either provided free bottled water or drinking water in a pitcher in the room.