My tank started leaking at the metal bands that hold it on the wall in my 98 U270. After getting a camera behind the tank it was fairly straight forward to remove it. I plugged the line and removed the tank. I was astonished to find the tank full of nasty rusted water. It's a two gallon Jabsco 18810-0000. It costs about $230. A Water Worker HT-2B is a quarter of the cost and same size, but reviews indicate it rusts out quickly, sometimes in less than a year.
I had not ever seen rusted water coming out of the faucets. Fortunately we filter all our drinking and cooking water. Is it common for these to be filled with rusty water? The pump seems to operate well without it, it's a Seaflow 3.0 GPM self priming pump that has been installed for about two years. We always operate from the fresh water tank, so it gets lots of use. I'm pretty sure this tank is original to coach.
They definitely do fail. Usually the bladder fails. When mine failed I noticed that the pump sounded different than usual. If you push the air valve pin on the tank and get water instead of air it's time to replace the tank. I got one at Home Depot for around $125.
Sounds like your bladder had been leaking for a while.
The Home Depot Logo (https://www.homedepot.com/p/Wilkins-18-l-Lead-Free-Potable-Water-Thermal-Expansion-Tank-XT-18/204079272)
The tank when working keeps your pump from having to cycle as much.
My 2014 do no even have one now. Have not missed it but the pump I have now is variable speed
They make a number of plastic pressure tanks - no rust - if you wish to replace your old tank.
Amazon.com : rv water accumulator tank (https://www.amazon.com/rv-water-accumulator-tank/s?k=rv+water+accumulator+tank)
The rusty water wouldn't get into your system as the rusty water would just stay inside the tank.
If you like the way it's been operating you can just take it out and plug it off as it probably hasn't
worked for quite awhile.