Half flush never seems to work right - am I missing something?

Have you checked if your tank’s flush valve seat is perfectly smooth? Sometimes a tiny bit of mineral buildup is all it takes to mess up the seal and start the ghost-flushing circus...

That’s a good point about the valve seat. Even a thin layer of scale can throw things off, especially with those dual-flush setups where the seal has to be just right for both flush volumes. I’ve noticed some kits are really finicky about the chain length too - if it’s even a link too short or long, the half flush either doesn’t trigger or dumps way more water than it should.

Out of curiosity, what brand/model are you working with? Some of the cheaper universal kits seem to have more issues with inconsistent half flushes, at least in my experience. Also, have you tried adjusting the float height or the actuator rod? Sometimes the half flush button doesn’t push the mechanism far enough, especially if there’s a bit of play in the button assembly.

I’ve run into a few tanks where the internal geometry just doesn’t play nice with aftermarket kits, no matter how much tweaking you do. Wondering if you’ve seen anything similar?

Funny you mention the chain length - last year I spent way too long fiddling with one of those “universal” dual-flush kits in my aunt’s old Kohler tank. No matter how I adjusted the chain, the half flush either barely trickled or just dumped the whole tank. Ended up realizing the button assembly was a hair off-center, so it wasn’t pushing the actuator rod down far enough for the half flush. Had to shim it with a bit of plastic to get it to line up right.

I’ve also noticed some tanks just don’t play nice with aftermarket kits, especially if the overflow tube is at a weird angle or the tank’s got a lip inside. Sometimes you can tweak things forever and it still won’t work quite right. Honestly, I’ve had better luck sticking with OEM parts when possible, even if they’re pricier.

Curious if anyone’s actually managed to get a perfect half flush on those older American Standard tanks? I swear, they’re cursed...

Half Flush Never Seems To Work Right - Am I Missing Something?

Man, I’ve been down this rabbit hole with those older American Standard tanks. I tried to retrofit my dad’s 90s-era one with a “universal” dual-flush kit last winter. Thought it’d be a quick upgrade, but it turned into a weekend project and a lot of cursing. The half flush was either a dribble or it just dumped everything, no in-between. I messed with the chain length, float height, even tried swapping out the flapper for a lighter one. Nothing really dialed it in.

What finally made me throw in the towel was the way the flush valve sits in those tanks. The seat is just a bit wider and the overflow tube is angled weird, so the aftermarket kit never really sealed right. I even tried trimming the gasket and using plumber’s grease to get a better fit, but it still leaked sometimes. At that point, I figured the water savings weren’t worth the headache.

I get what you mean about OEM parts being pricey, but honestly, they’re usually less hassle in the long run. The only time I got a half flush working halfway decent was when I found an old stock American Standard dual-flush conversion kit on eBay. Even then, it took some fiddling and it still wasn’t perfect - sometimes you’d get a full flush when you wanted half, depending on how hard you pressed the button.

I’ve started telling people if their tank’s more than 15 years old and they want dual-flush, just replace the whole toilet if you can swing it. Otherwise, you’re probably in for a lot of trial and error and maybe some creative shimming like you did. Those “universal” kits are more like “universal-ish,” especially with older models.

If anyone’s actually gotten a perfect half flush on those tanks without losing their mind, I’d be impressed. Maybe there’s some secret trick out there, but I haven’t found it yet...

Tried the same thing with a Fluidmaster kit on my early 2000s tank. Half flush was either useless or just as much water as a full flush. I kept tweaking it for weeks, but honestly, I think these old tanks just aren’t built for it. Ended up sticking with the original setup - less hassle, and at least it works every time.

- Totally get where you’re coming from.
- Older tanks just weren’t designed for dual flush, so retrofits can be hit or miss.
- I tried a similar kit on a ‘99 model and had the same issue - half flush barely moved anything, or it’d dump almost as much as a full flush.
- Sometimes the mechanics just don’t line up with the original design.
- At least you gave it a shot - sometimes sticking with what works is the most eco-friendly option if it means fewer headaches and less wasted water fiddling with fixes.