How to talk to a bartender who pours drinks light without being the asshole

Telling a bartender that they are pouring light is something I scrupulously avoid since most of the time it is just an accident, and bartenders really don’t like to hear it.

But there is one bartender who has consistently poured much lighter than the others, at a bar where I am a regular. I get the sense that they see me tipping 50 percent and think I will drink more drinks if they pour light so they will get more tips. This is a dive bar where typical pour seems 2oz and they seem to pour 1oz.

This has happened on 5 visits so far.

I have started reducing my tips to her to 30 percent, and last time left after 3 drinks where I usually have 5-6.

This passive aggressive approach feels icky and I wonder if there is a way to communicate directly without being the asshole.

Giving them the benefit of the doubt, maybe they think they are helping reduce hangovers by increasing my mixer (soda) intake. I was thinking of letting them know that I usually chug some water in the bathroom between drinks, but that seems weird to say. Maybe just asking for waters after every drink would eliminate that concern.

But I suspect it’s not done for altruistic reasons, and if so perhaps somehow letting them know that I see their game would encourage them to knock it off.