White flakes or particles in your tap water are almost always calcium carbonate, pipe scale, or mineral deposits breaking loose somewhere between the water main and your faucet. They’re usually harmless but worth tracking down, because the source tells you whether you’re looking at a minor nuisance or something that needs attention soon.
The Most Common Culprits
Calcium and magnesium deposits (hard water scale)
If you’re in California, your water is almost certainly hard. Dissolved calcium and magnesium are invisible while in solution, but they precipitate out as white or off-white scale when water heats up or sits in pipes long enough. You’ll see this most often from the hot water side, as little chalky flakes or a fine white cloud that settles quickly in a glass. Run cold-only for a minute, then hot-only, and see which side the particles come from. That tells you a lot.
Water heater breakdown
This is the most likely single source for heavy white particle loads in hot water. Water heaters accumulate scale on the tank bottom over years. When sediment builds up and the tank’s interior surface degrades, it can shed white or gray-white flakes into the water. If your heater is over ten years old and you’re seeing particles predominantly in hot water, the heater deserves a look. Flushing the tank (draining a few gallons from the drain valve) sometimes dislodges sediment and temporarily reduces particles, but it doesn’t fix a failing tank or a cracked dip tube.
Dip tube disintegration
This one is worth knowing about. The dip tube is a plastic pipe inside the water heater that routes cold incoming water down to the bottom of the tank so it heats efficiently. Older polypropylene dip tubes, particularly in heaters made between roughly 1993 and 1997, can get brittle and crumble over time. The debris looks like small white plastic pieces or pellets. You might also notice reduced hot water pressure or lukewarm water before the tank should be empty. Pull the aerator screens off a few faucets and look for white plastic-looking fragments; if you find them, a failed dip tube is a strong candidate. One quick field test: calcium scale dissolves in white vinegar; plastic fragments don’t.
Plastic supply line deterioration
Flexible braided supply lines under sinks or behind toilets can degrade over time. If particles are localized to one fixture, check its supply line for visible bulging, kinking, or cracking. This is worth inspecting not just for the particle issue, but because a failing supply line can rupture and flood the room.
Galvanized or older copper pipe corrosion
Older galvanized steel pipe corrodes from the inside and most often sheds rust-colored or brownish material, but calcium-coated debris on those surfaces can flake off as white material when disturbed by pressure changes or repairs upstream. Copper pipe corrosion usually shows up as blue-green or brownish, not white, but calcium deposits on copper surfaces can do the same.
Municipal water treatment residue
Occasionally white cloudiness or particles come from the water supplier, usually after maintenance work on the distribution system. This typically clears within a few hours to a day. Run a cold tap for a couple of minutes and see if it clears. If it does, it’s likely a temporary event. If it persists, the source is inside your home.
How a Plumber Diagnoses It
A licensed plumber will isolate the problem by testing cold and hot sides separately, pulling aerator screens at multiple fixtures, and checking what’s in the water heater drain. If particles only appear on the hot side, the heater is the primary suspect. If particles appear at one fixture only, the supply line or fixture valve is likely. If every tap in the house has it, the problem is upstream.
They may also do a basic water hardness test on-site. For more detailed analysis, a water sample sent to a lab can identify minerals and rule out contaminants. Most plumbers can get a strong working diagnosis from visual inspection and isolation testing without needing a lab.
Quick Checks Before You Call
Aerator screens accumulate debris and are easy to inspect. Unscrew the aerator at the tip of the faucet, rinse it, and soak it in white vinegar for an hour if scale is blocking it. This tells you how fast deposits are building up and costs nothing.
Checking under-sink supply lines visually for bulging, kinking, or cracking is quick and worth doing. A failing braided line can rupture without much warning.
Annual flushing of the water heater’s drain valve is standard maintenance that can reduce sediment load. If you haven’t done it before, or if the heater is old and you’re not sure the drain valve will re-seat properly after being opened, have a licensed plumber handle it. An old valve that won’t close after flushing turns a maintenance task into an emergency.
Everything beyond those checks needs licensed work. Replacing a water heater, cutting into supply lines, or testing for lead requires a licensed contractor with a permit in California.
When to Call a Licensed Plumber
Call a licensed plumber if:
- Particles are brown, orange, or rust-colored (suggests pipe corrosion that may affect water quality)
- White flakes are accompanied by reduced pressure, strange smells, or discolored water that doesn’t clear
- Your water heater is over ten years old and producing significant sediment in hot water
- You suspect a failing dip tube (plastic fragments in aerator screens)
- A supply line looks swollen or kinked and you’re seeing particles from that fixture
- You’re on a well and notice a sudden change (different diagnostic entirely)
For routine white scale buildup in a hard-water area, a whole-house water softener is often the long-term fix. That’s a bigger installation job, and the right approach depends on your water hardness level and piping.
Before hiring anyone, verify the plumber’s license at cslb.ca.gov. California requires a C-36 Plumbing Contractor license for most plumbing work. This is an information guide only. We don’t perform plumbing work, and nothing here is a substitute for a licensed plumber’s on-site diagnosis.