drinking water

Generally not a good idea to risk contamination in these countries. Just use bottled water.

is the water in Vietnam suitable

Suitable for for showering and washing your clothes yes. As for drinking I'd recommend bottled water. Even where the water is perfectly safe you're likely to get a case of the runs simply because it's different water than you're used to. Stick with bottled water.

Agree with drinking bottled water - Aquafina or La Vie!

You are casting a strange question!

You had better know the fact below as not to cause abdominal pain in other countries!!

The number of countries where the tap water is drinkable is 15 only now in the world .
↓
Japan/Finland, Sweeden, Iceland, Ireland, Garmany, Austrie, Slovenia, Croatia/United Arab Emirates=UAE/South Africa, Mozambique(!), Lesotho(!)/Australia, Newzealand
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
the order of tap water's cleaness---Japan＞Iceland＞--＞--＞---

As for tap water in USA, Canada, France, Italy, Spain, etc----＜X＞=not drinkable, and of course, tap water in China, Vietnam & all other SEA countries---＜XXX＞=never drinkable as it is!

During to trips, washed and cleaned my teeth in tap water.
#2, I go the other way, no matter how much I drink and eat meals with chillies.

Local people overhere still drink boiled tap water or rain water.

Just to be on the safe side, I'd use bottled water to brush your teeth as well. I met some fellow travelers there this month who said they had been a bit sick, even though they had stuck with bottled water. The first thing I asked them was how they had brushed their teeth - and they had used tap water. Of course that may not have been the problem.

Dear All,

Thanks a lot for your feedback!

I'm surprised that nobody has bothered to challenge #4. I'd be interested in seeing the source of his claim.