Hard water stains on a stainless steel sink come off with a mild acid: wipe on white vinegar or a diluted citric acid solution, let it sit a few minutes, rub along the grain with a soft cloth or nylon pad, then rinse with clean water and dry. Do not use steel wool, chlorine bleach or gritty powders, which scratch the surface and can lead to rust.
Shop the equipment in this article: three compartment sinks, hand sinks and commercial sink faucets. Freight is included on every order.
What hard water stains look like
Hard water stains are mineral deposits, mostly calcium and magnesium, left behind when water dries on the steel. You see them as a white ring at the waterline of each bowl, a cloudy film on the bowl walls, a chalky crust around the faucet base and drain, and spots on the drainboard where racks sat wet. They feel rough when you run a fingernail across them. Orange or brown spots are a different problem: that is rust, usually from iron particles or chlorine, and it needs a different method, covered in our guide to removing rust spots from stainless steel.
The stains build up fastest on the sinks that work hardest, such as a commercial kitchen sink with three compartments used for pots, pans and bar glassware all day.
What you need
- White vinegar, or citric acid powder mixed with warm water as the package directs
- A spray bottle
- Soft cloths or a non-scratch nylon pad
- Clean water for rinsing
- A dry towel
These are common practice choices for mineral deposits on stainless steel. If the sink came with care instructions from the manufacturer, follow those first.
Step by step
- Drain the sink and clear out dishes, racks and the strainer baskets.
- Rinse the bowls with warm water to remove grease and food soil. Acid works on minerals, not on grease.
- Spray the stained areas with vinegar or the citric acid solution until they are wet.
- Lay a cloth soaked in the same solution over heavy crust, such as the ring around the drain or the faucet base, and leave it for 10 to 15 minutes.
- Wipe or scrub lightly with the nylon pad, moving along the grain of the steel, not in circles.
- Repeat on stubborn spots. Thick scale usually comes off in two or three rounds.
- Rinse every surface well with clean water so no acid is left on the steel.
- Dry the sink completely with a towel.
- Wash, rinse and sanitize the bowls before the sink goes back into use for dishes.
What not to use
- Steel wool or wire brushes. They scratch the surface and leave carbon steel particles that rust.
- Chlorine bleach or cleaners with chlorides on dry stains. Chlorides attack stainless steel and can cause pitting and rust spots.
- Strong acid cleaners not made for stainless steel. Some are sold for masonry or drains and can etch the surface.
Why it matters for food safety
The FDA Food Code requires food-contact surfaces of equipment and utensils to be clean to sight and touch, and non-food-contact surfaces to be kept free of an accumulation of dust, dirt, food residue and other debris (Food Code 4-601.11). A crusted sink bowl is harder to clean and harder for an inspector to accept as clean.
Hard water also affects the sanitizing step. Under Food Code 4-501.114, a quaternary ammonium sanitizer may be used only in water with a hardness of 500 mg/L or less, or no harder than the sanitizer label allows. If your water is very hard, check the label of the quat you use and test the solution with the strips made for it. Your local health department has the final say on how sinks and sanitizer are checked in your kitchen.
How to keep the stains from coming back
- Drain and dry the bowls and drainboards at the end of each day instead of letting them air dry overnight.
- Wipe the faucet base and the area around the drain at closing, where water sits longest.
- Clean the faucet aerator when the stream starts to spray or splash, since scale builds up there too.
- Use the vinegar wipe once a week on hard water, before the film turns into crust.
- If you install a water softener or filter, have it serviced as the manufacturer says and keep the service records. The Food Code requires that for water treatment devices (Food Code 5-205.13).
What our sinks are made of
Our sinks are stainless steel throughout, so the same method works on all of them. The 36 in. drop-in three compartment sink, model DIS-S3C-101410-F, is 18 gauge stainless with three 10 x 14 x 10 in. bowls in a 36 x 18.5 in. footprint, and comes with a faucet and basket strainers; it is listed on backorder at the moment. The underbar three compartment sink with three 14 x 10 x 10 in. bowls is 18 gauge type 304 stainless, and our underbar hand sinks are type 304. Hard water stains any grade of stainless steel if it is left to dry wet day after day.
What to buy
If your sink is pitted, cracked at the welds or too small for your largest pans, it may be time to replace it rather than descale it. Compare sizes in our three compartment sinks, hand sinks and underbar bar sinks, and add a new faucet from our commercial sink faucets if the old one is crusted beyond cleaning. Express KitchQuip stainless steel sinks are NSF certified, and freight to the 48 contiguous states is included in the price.