Sediment/flakes in hot water

Question

For the past year or two, I’ve been seeing a lot of these hard brittle flakes coming out of all the faucets in my house (kitchen sink, bathroom sinks, and shower/tub).

Now that I actually have the time and funds to work on this, I’d like to get this fixed!

The flakes only occur in hot water, and clog the shower head. The water is from a city main line, not a well, and we also do have quite hard water. What can I do to diagnose and/or fix the issue?

Some history of the water heater:

• It's a relatively new Noritz tankless water heater, installed about 2 years ago. It replaced an older Noritz tankless heater, which came with the house.
• There used to be a water softener attached to the water heater, but we disconnected it awhile ago since it was old and we suspected it was the source/cause of the flakes.

Here’s a picture of the flakes, for reference:

Answer 1

If you have a tank-type heater, flush the tank.

Beware that if the tank drain has not been used, it may fail to seal well after being used to flush the tank (so try to schedule the operation for when the stores are open and you can go get another one.)

A water softener (at least on the supply to the water heater) is probably advisable since you have hard water from the city, and heating it tends to cause stuff to come out of solution. Your flakes are mostly limestone (calcium carbonate, dissolved in the water, which comes out of solution as the water is heated), in most parts of the world.