[hypoxia]

Whoa...that's an interesting find! And, TBH, could be the reason so many have issues with the HH toilets!

My mistake, I edited that post.  The water shutoff valve from the tank to the water pump and the toilet water supply shutoff valves are 3/4" brass but the water supply line is 1" (0.875" ID) PEX.  GROK says the short runs in a motorhome are OK with that sizing.  All I know is the toilets do struggle with some flushes.  1482 was originally spec'd with SeaLand 500 Marine Toilets.  In 2018 the mid bath was replaced with the Headhunter Royal Flush.  The rear bath was also changed, I don't have the documentation for that.