This is also a common complaint when folks drain the hot water heater through the low point drains instead of bypassing and removing the anode.
Bits of anode material and calcium chunks get swept into the tubing and when you do finally pressurize the system, that junk gets pushed everywhere. (Faucets, shower head and flush valve)
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW