It seems like a silly question for most of my travels, as I 'll be in a hotel, but I will travel a little bit.
It depends on who you ask, basically.
The latest report I can find states that it's "safe to drink - for now".
The water quality is managed by The Manila Water Company, and they do monthly checks of over 1000 samples.
However, it's also worth noting the article points out that during rainy season, the risk of contamination is higher from pipes being submerged in floodwaters.
However, that's the "official" report. The article goes on to say:
Officials often claim that water is safe to drink in Manila but foreigners are advised not to drink tap water, even those served in fine restaurants. Restaurants may also say that their water is boiled and/or filtered but they often use tap water. Travel agencies and other officials advise that visitors in the Philippines only take mineral or bottled water that is sealed when unopened.