Quick answer
When a good man gives way under pressure, something a community depended on stops being drinkable. The verse measures the loss in public terms.
Read both lines
Springs and wells were not private amenities. They were the water supply, the thing an entire settlement organized itself around, and fouling one was a communal disaster rather than a personal misfortune. That is what the comparison is doing: it locates the damage in everyone who was drinking.
The verb behind "falters" means to totter or give way, so this is collapse under pressure rather than corruption over time, and the pressure is named, before the wicked. The saying does not condemn the man. It grieves what happens around him, and the NKJV footnotes the second image as ruined. There is a real pastoral weight here: people who have been steady for others are load-bearing whether they agreed to be or not, and this book knows it.
Related: Proverbs 24:15–16 · Proverbs 10:11 · Proverbs 28:12 · Proverbs 29:2
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.