Honestly, I think a lot of it comes down to the specific model and how well it’s installed. I’ve swapped out a few toilets over the years, and some of the newer dual-flush ones actually do a decent job with the half flush—at least for liquids. But yeah, I’ve run into the same issue where the half flush just doesn’t cut it for anything more than that.
I wouldn’t say it’s always a design flaw, though. Sometimes it’s the way the rim jets are aimed or even how the bowl is shaped. I had one Toto that worked surprisingly well, but a cheaper off-brand one was basically useless unless you hit the full flush every time.
Pressure definitely plays a part, but I think manufacturers are still figuring out the sweet spot between saving water and actually clearing the bowl. It’s kind of a gamble unless you do a ton of research before buying. Personally, I’d rather have something reliable than save a couple gallons here and there if it means double flushing all the time.
Had a similar experience with a dual-flush at my cousin’s place. The half flush was basically just for show—anything more than a bit of tissue and you’d be reaching for the handle again. I’ve noticed that some bowls just don’t have the right slope or water spot, so stuff gets left behind. Kinda wild how much difference a few millimeters in design can make. I get the water-saving thing, but if you’re flushing twice, what’s the point?
You’re not alone—some of those dual-flush setups just don’t cut it. I’ve swapped out a couple in my rentals because tenants kept complaining. Sometimes it’s the bowl, sometimes the valve just isn’t calibrated right. It’s wild how a tiny design tweak can make or break the whole thing. If you’re flushing twice, it kind of defeats the purpose, yeah.