"Drinking water": This would be water that is safe to drink. It can come from a tap or a bottle.
"Filtered water": This again is water that has been through a filter system to get out impurities and can be either from a tap or in a bottle.
Hope that helps :)
It rather depends which country you are in when you try to define what is, or is not, drinking water. In the UK, water from the tap is safe to drink, so people may well request ' A glass of tap water," if they are thirsty. Bottled water should be safe to drink in any country. If water is tainted by salt or impurities, or is dangerous to drink, then it is said to be 'undrinkable.' 'Potable' is a lesser used adjective.
どこの国にいるかにもよりますが、イギリスでは、水道水は安全に飲むことができるので、' A glass of tap water,"（水道水一杯）欲しいと頼まれるかもしれません。 Bottled water （ボトルウォーター）もどこの国でも安全です。
もし、水が濁っていたり、不純物が入っていたりして、飲むのに危険な場合は、'undrinkable.'（飲むことができない）と言われます。 'Potable' は飲料に適したという意味の形容詞として使われます。
海外では本当に水には注意したいですよね。
「飲料水」自体はdrinking waterという言い方で通じます。
ただ、「この水は飲料水ですか？」つまり「この水は飲むことができますか？」という意図の質問をされる場合には、
Is it OK to drink this water?
「この水は飲んでも大丈夫ですか？」
のような聞き方が自然です。
OKをsafe「安全な」という単語に代えて、
Is it safe to drink this water?
「この水は飲んでも安全ですか？」
と聞いてもいいです。
他には、
Is this water drinkable?
「この水は飲むことが可能ですか？」
という聞き方も使えます。
※ableは「可能」を意味します。drink「飲む」にくっつけてdrinkableで「飲むことが可能な」という意味になります。
または、シンプルに
Can I drink this water?
「この水を飲むことはできますか？」
と聞いても十分伝わります。
ご参考になれば幸いです。
Water from the tap in the UK is drinkable (safe to drink) so you could simply ask for a 'glass of tap water'. In some countries the tap water is not safe to drink out the tap so you would use 'bottled water' instead. The term 'drinking water' means that it is safe to drink so the person would then know what to give you depending on the country
Potable means safe to drink
'When we go on our hike we must ensure we have adequte potable water otherwise we risk getting sick'
Ensure = make sure, make certain
Adequate = enough, sufficient
'Could you sell me some drinking water please? One litre bottles'
'Is this tap water safe to drink? It looks rather dirty'
potable'は「飲むのに安全」という意味です。
例文
'When we go on our hike we must ensure we have adequate potable water otherwise we risk getting sick'
（ハイキングに行く時は、十分な飲料水を持っていかなくてはなりません。でないと、体調を崩すことがあります）
Ensure = ～を確実にする
Adequate = 十分な
例文
'Could you sell me some drinking water please? One litre bottles'
（飲料水を売って頂けませんか？1Lボトルでお願いします）
'Is this tap water safe to drink? It looks rather dirty'
（この水道水は飲めますか？汚く見えます）
"Drinking water" is a term that can be used in one of two ways. It can be used as a verb where one may be literally drinking water or it can be used as a noun where one is describing the nature of the water and its cleanliness. If the water is clean enough for one to drink safely, then it is considered drinking water. Or in a metaphorical sense, if the water lives up to one's standard, then they may consider it drinking water.
南アフリカ 
イギリス 
日本 
アメリカ合衆国 
