If you have a floor drain plan on removing the drain bib and poking the sediment out. Older units clog up easily.

You can try power flushing it before you cut off the water supply but they'll usually clog up anyways.

As mentioned newer units have thicker insulation so they're bigger in all directions this may cause difficulty if they're next to something or behind a doorway that is smaller

Is it gas or electric?

If its gas, stand next to it when it's running and listen. The popping noise is calcium and sediment in the bottom expanding under heat
The more and louder the pops the more junk inside.