水道, 給水, and 排水: supply systems, water delivery, and wastewater
Follow 水道 in supply shutoffs and faucets, 給水 in water delivery and water stations, and 排水 in drains and wastewater. Distinguish available water from water actually drunk, and identify what is treated.
水道: the water system and its faucet
水道 is read すいどう. 「工事のため午後まで水道が止まる。」 says the water supply will be shut off until the afternoon for construction. 水道 names the supply that will be interrupted.
「水道の蛇口から水が少し漏れている。」 says water is leaking slightly from the faucet. 水道の蛇口 names the faucet connected with the water system, and から marks the source of the leaking water.
給水: receiving water and the water station
給水, read きゅうすい, refers to water supply. 「断水中は公園で給水を受けられる。」 says water is available at the park while the supply is cut off. 受けられる expresses the possibility of receiving it, rather than reporting completed receipt.
「走者は給水地点で少しずつ水を飲んだ。」 says the runners drank a little water at the water station. 給水地点 names the supply point. The completed action of drinking is expressed by 水を飲んだ.
排水: a drain or the wastewater treated
排水 is read はいすい. 「大雨に備えて、屋上の排水口を掃除した。」 says the roof drain was cleaned in preparation for heavy rain. 排水口 names the opening through which water drains.
「工場の排水は、基準を満たすまで処理される。」 says factory wastewater is treated until it meets the standards. Here 排水 names the wastewater being treated, rather than just the action of drainage. The sentence provides no numerical standard or treatment method.
What does 排水 name in 「工場の排水は、基準を満たすまで処理される。」, and how does that differ from the 水道 and 給水 examples?
Show the answer and why
It names factory wastewater, the object of treatment. 水道 names the water supply or combines with the faucet, while 給水 concerns receiving water or the water station. Reading 排水 only as a drainage action would miss the wastewater being treated.