23 minute dump time?
He most likely had a macerator pump. That takes FOREVER to dump. Like the septic system needs the waste macerated.
I had a guy parked next to me that had one and you heard the macerator motor churning for OVER 25 minutes every time he dumped! :R
Don't get me wrong the noise didn't bother me but his dump pipe ran past mine so I had to make sure he was done with his ridiculous 25 minutes to dump a tank before opening my sewer cap.
Just don't see the need for those. Unless you are parked at home and need an uphill dump fix.