My trailer is just about 4 years old. I noticed the last time I open my low point drains that there was calcium sediment coming out of the hot water side.
I picked up the tools ($15) in the photo below to loosen the drain bolt and flush the bottom sediment of the hot water tank.
I use a water filter but not a water softener. I ended up having about a teaspoon or so of calcium come out in the flush water. I was surprised at the sandy consistency of the sediment considering the size of the pellets came out in my low point drain exercise a few weeks ago.
I just wanted to share my experience.