The flow at one faucet has dropped to a trickle. Everything else in the house is fine. You unscrew the tip and there it is, a crust of chalky white mineral packed into a fine mesh screen.
That is calcium, and clearing it takes about twenty minutes. The part worth knowing is that the same deposit is forming in six other places you cannot see.
What to Do Right Now
Unscrew the aerator and soak it in white vinegar for four hours. That dissolves calcium and restores flow at a cost of nothing. Most clogged faucets are fixed in one step.
If flow is still low after cleaning, the deposit has moved past the aerator into the cartridge or the supply line, and cleaning the tip will not reach it.
If you are doing this more than once or twice a year, you are treating a symptom on a schedule. The water is the problem.
Is It Actually Calcium?
Low flow at a faucet has several causes and they get treated the same way by mistake. This is how to tell them apart before you take anything apart.
| What you see | Cause | What fixes it |
|---|---|---|
| One faucet only, white chalky crust on the tip, flow improves briefly after cleaning | Calcium in the aerator | Vinegar soak |
| One faucet, no visible crust, flow never recovers after cleaning | Cartridge or angle stop | Cartridge replacement |
| Hot side only | Scale in the water heater or a failing dip tube | Flush the tank |
| Rust-colored flakes rather than white crust | Corroding galvanized pipe | Not a cleaning problem |
| Every fixture in the house | House pressure, regulator or main line | Pressure test |
| Sudden after plumbing work | Debris knocked loose in the line | Flush all fixtures |
Only the first row is what this page is about. If the flow does not come back after a proper soak, the problem is downstream of the screen and faucet low water pressure covers the rest of the list.
How to Clean a Calcium-Clogged Aerator
- Close the drain first. Aerator screens come apart into three or four small pieces and they are gone the moment one goes down the drain.
- Unscrew the aerator. Most turn by hand. If it is stuck, wrap the tip in a cloth before using pliers so you do not mark the finish.
- Photograph it before disassembly. The screen, the flow restrictor and the rubber washer go back in a specific order and a specific direction.
- Soak in plain white vinegar, four hours minimum. Overnight on a bad one. The acetic acid dissolves calcium carbonate. Warming the vinegar slightly speeds it up.
- Brush the screen with an old toothbrush and rinse. Do not pick at it with anything metal, the mesh deforms easily.
- Run the faucet before reassembly for ten seconds to flush whatever broke loose inside the spout.
- Reassemble and hand-tighten only. Overtightening crushes the washer and causes a drip at the tip.
What not to use
No bleach. It does nothing to calcium and degrades the rubber washer.
Careful with commercial descalers on brushed nickel, oil-rubbed bronze and matte black. They strip finishes, and the damage is permanent. Vinegar is slower and safe on everything.
Never soak a whole faucet body in anything acidic. It reaches internal seals you cannot inspect.
While the aerator is off, check the showerhead in the same bathroom. It is fed by the same water and is almost always in the same condition.
What Else It Is Clogging That You Cannot See
The aerator is the only place calcium is visible. It is not the only place it lands.
| Where | What it does | What you notice |
|---|---|---|
| Showerhead nozzles | Blocks individual jets | Spray goes uneven or sideways |
| Faucet cartridge | Restricts the valve internals | Flow stays low after cleaning the tip |
| Water heater tank | Insulating layer on the floor of the tank | Popping, higher bills, less hot water |
| Dishwasher inlet screen | Restricts fill | Longer cycles, film on glassware |
| Ice maker line | Narrows a very small tube | Smaller cubes, then none |
| Supply piping | Reduces internal diameter over years | Whole-house pressure drifts down |
The water heater is the expensive one. Scale on the tank floor makes the burner work through a layer of rock, which is what causes the popping and rumbling people hear from older tanks and what shortens their life.
The supply piping is the slow one. Scale narrowing pipe diameter over decades is a real mechanism rather than a sales line, and what hard water does to pipes sets out how fast it happens on Houston water.
How Hard Is Houston Water?
Hardness is measured in grains per gallon, and it is simply the amount of dissolved calcium and magnesium in the supply. The USGS scale calls anything above 7 gpg hard and above 10.5 very hard.
| Supply | Typical hardness | Classification |
|---|---|---|
| City of Houston tap water | 7 to 8 gpg | Hard |
| Suburban MUD well water, Katy, Cypress, NE Harris | 11 to 17+ gpg | Very hard |
That range is why two neighbors two streets apart can have completely different experiences with the same faucet. A house on city water at 7 gpg cleans an aerator once a year. A house on MUD well water at 15 gpg does it every few months.
Hardness is not a health issue and is not regulated as one. The EPA lists it under secondary standards, which cover taste, odor and nuisance effects rather than safety. It is a maintenance and equipment problem, not a drinking water problem.
When Cleaning Stops Being Enough
Cleaning an aerator is the right first move. It stops being the right move when any of these are true:
- You are doing it more than twice a year at the same fixture
- Flow does not fully return after a proper four-hour soak
- Multiple fixtures need it at the same time
- The water heater has started popping, which means the tank floor is already covered
- Glassware comes out of the dishwasher filmed regardless of detergent
At that point the decision is about equipment, and the distinction that trips people up is that a softener and a filter do different jobs. A filter improves taste and removes contaminants. A softener is the only one of the two that removes the calcium and magnesium causing this. The difference is set out in water filtration system vs water softener.
Before you buy anything, test
Softeners are sized to your actual hardness and household water use. Sizing to a guess means either overspending or a unit that regenerates constantly and wastes salt.
A hardness test takes a few minutes. water softener installation covers sizing, running costs and what the install involves.
Frequently Asked Questions
What do I do about a faucet clogged by calcium?
Unscrew the aerator from the faucet tip, photograph the parts before taking it apart, and soak everything in plain white vinegar for at least four hours. The acetic acid dissolves calcium carbonate. Brush the mesh screen with an old toothbrush, rinse, run the faucet briefly to flush the spout, then reassemble hand-tight. That restores flow on most clogged faucets.
Why does calcium clog the faucet and not the rest of the plumbing first?
It does not clog the faucet first, it just becomes visible there first. The aerator holds a fine mesh screen at the very end of the line, so it catches anything that has broken loose anywhere upstream. The same deposit is forming in the showerhead, the faucet cartridge, the water heater tank, the dishwasher inlet and inside the supply pipes. The aerator is simply the one place you can unscrew and look at.
How long should I soak an aerator in vinegar?
Four hours minimum, and overnight on a badly clogged one. Warming the vinegar slightly speeds the reaction. There is no benefit to stronger acid: plain white vinegar dissolves calcium carbonate fully given time, and commercial descalers can strip brushed nickel, oil-rubbed bronze and matte black finishes permanently.
Can I use CLR or bleach to clean calcium off a faucet?
Bleach does nothing to calcium and degrades the rubber washer inside the aerator. Commercial descalers do dissolve it, but they can strip finishes on brushed nickel, oil-rubbed bronze and matte black fixtures, and that damage cannot be undone. White vinegar is slower and safe on every finish. Never soak a whole faucet body in anything acidic, because it reaches internal seals you cannot inspect.
How hard is Houston water?
City of Houston tap water runs about 7 to 8 grains per gallon, which is classified as hard. Suburban areas on MUD well water, including parts of Katy, Cypress and northeast Harris County, commonly test 11 to 17 grains per gallon or higher, which is very hard. That difference is why two homes a few streets apart can have very different experiences with the same faucet.
My faucet is still slow after cleaning the aerator. What now?
The restriction is downstream of the screen. The usual culprits are scale inside the faucet cartridge, a partially closed angle stop under the sink, or debris in the supply line. If only the hot side is slow, the problem is more likely the water heater or a failing dip tube than the faucet. None of those are fixed by cleaning the tip.
Is hard water dangerous to drink?
No. Hardness is dissolved calcium and magnesium, and the EPA classifies it under secondary standards, which cover taste, odor and nuisance effects rather than health. It is a maintenance and equipment problem: scale in the water heater, shorter appliance life, film on glassware and restricted fixtures. Not a drinking water safety issue.
Will a water filter stop calcium buildup?
No. A filter improves taste and removes contaminants but leaves dissolved calcium and magnesium in the water, so scale keeps forming. A water softener is the only one of the two that removes the minerals causing the buildup. This is the most common mix-up we hear, and buying the wrong one means the faucets keep clogging on the same schedule.
Cleaning the same aerator every few months?
We test hardness at your tap and size a softener to your actual numbers rather than a guess. Free estimates across Houston and the surrounding counties.
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