snip
Vinegar will help dissolve some mineral deposits. You can also use
the cleaner sold for coffee pots.

Also may want to disinfect, especially if the smell is musty/moldy.
Unplug or turn off power, fill with weak solution of chlorine laundry
bleach and water, let sit for 30 minutes or more, and then flush until
bleach odor is gone.

Some of these units have copper tanks. Some are plastic. I'd
be really careful about using bleach for any significant time on copper.
For that matter, the heating elements in the plastic ones could be
destroyed by it also.

Bob



Diluted bleach is routinely used to disinfect water systems,
particularly well water systems. Copper will react with highly
concentrated chlorine bleach, but it is a very slow reaction,
especially at room temperature. 30 minutes with diluted bleach will do
no harm whatsoever.

I've not seen an insta-hot with a plastic tank, although many have
plastic shrouds. If the heating tank itself is plastic, then I'd check
with manufacturer for disinfection instructions.

Paul