Everything You Need To Know About Silica In Your Water

David Brewster | September 10, 2020

Silica is a mineral compound with the formula SiO₂ . This very common mineral has many different forms and is most easily recognized in nature as the mineral quartz.

Silica is actually silicon dioxide. Silicon is the 7th most abundant element in the universe and the second most abundant element in the Earth’s crust, after oxygen. In fact, the vast majority of all rocks are comprised of silicate minerals which have SiO₂ as their fundamental building block.

Although the solubility of silica in water is low, and the dissolution rate of silicate minerals is very slow, its sheer abundance means that is present in ground water supplies at some level.

Anyone with a granite countertop in their home can see silica (quartz) as well as a range of silicate minerals just by studying the minerals present in their countertops. It is no wonder that wells drilled into normal rocks pick up silica over the span of years as the groundwater slowly dissolves the rocks.

Silica, also known as silicon dioxide (SiO₂), is one of the most abundant minerals on Earth. If you’ve ever looked closely at a granite countertop, you’ve seen silica in the form of quartz and silicate minerals. Because it’s everywhere in rocks and soil, silica often makes its way into groundwater and private wells.

Although silica isn’t considered harmful to human health, it can cause frustrating household problems, especially stubborn deposits on glass, fixtures, and plumbing. Understanding how silica gets into your water, what it does, and how to manage it can save you time and money.

How Silica Gets Into Water Supplies

Silica enters water through a slow process: groundwater gradually dissolves rocks and minerals rich in silicon dioxide. While the solubility of silica in water is low, its abundance in nature means that nearly every well has at least trace amounts.

Silica exists in two main forms in water:

Reactive silica: Dissolved in water as bisilicate ions, behaving like a weak acid. It can be reduced using specialized ion exchange resins, but regeneration requires strong chemicals like caustic soda, so this method is limited to industrial applications.
Colloidal silica: Ultra-fine particles suspended in water that resist normal filtration. This type cannot be removed by ion exchange and is especially challenging in residential settings.

Signs of Silica in the Home

Problems typically appear when silica concentrations reach about 20–25 mg/L. Common household signs include:

Etching on glassware from dishwashers, leaving a milky or rainbow sheen
Hard, white lines in toilet bowls that require scraping or pumice to remove
Stubborn spotting on polished chrome, black porcelain sinks, and shower doors
A frosted look on glass shower panels
White film or buildup on granite countertops

Unlike calcium-based scale, silica deposits are extremely tough. Traditional descaling acids won’t remove them, and once glassware is etched, the damage is permanent.

Common Places to See Silica Deposits

Water line in toilet bowl - vary hard build up can only be removed with pumice stone or scraping

On polished chrome surfaces like tub fixtures

Obvious on black porcelain sinks and surfaces as hard white spots, "islands", or spidery networks

Silica domains on glass shower doors - "frosted look"

Dull, white silica build-up on granite counters

The most common attribute of all silica deposits is how hard and stubborn they are. These deposits are very tough and normal calcium scale removers (acids) will not remove silica deposits.

Treatment Options for Silica in Water

Silica removal is one of the most difficult water treatment challenges. Options include:

Lime-soda softening
A chemical process that precipitates silica by raising the pH with lime and soda ash. Effective, but impractical for residential homes.
Ultrafiltration
Specialized membranes can capture colloidal silica in industrial settings. These systems are expensive and not designed for home use.
Anion exchange
Works for reactive silica but not colloidal silica. Requires hazardous regeneration chemicals, so not suitable for residential applications.
Whole-house reverse osmosis (RO)
The most practical option for homeowners. RO can reduce both reactive and colloidal silica, but the system must be properly sized and often requires pretreatment for hardness and iron.

Because treatment is complex, many homeowners focus on prevention and mitigation instead of full removal.

Mitigating Silica Deposits at Home

If you live in an area with high silica levels, these steps can help minimize damage:

Keep dishwasher water temperature below 140°F to reduce etching
Use phosphate-free, soft-water detergents and allow dishes to air-dry
Hand wash delicate glassware instead of running it through the dishwasher
Wipe down chrome fixtures and shower glass to prevent spotting
Clean toilet bowl water lines before buildup hardens, using specialized cleaners like AMAZ
For existing silica stains, use products formulated for silica removal; some contain hydrofluoric acid (HF) and should be handled with extreme caution
Apply protective coatings like Rain-X on shower doors or glass to reduce spotting

Key Takeaway

Silica in your water won’t harm your health, but it can damage your home’s fixtures, glass, and plumbing over time. Whole-house RO systems are the most effective residential treatment, but prevention and regular maintenance remain the most practical strategies for most households.

Evidence of Silica In The Home

We have found that when the concentration of silica in ground water reaches levels of about 20-25 mg/l, silica deposit problems may become apparent in the home. There are several areas where silica deposits are common.

Silica Etching of Glassware

All glass is primarily comprised of SiO₂ as the major constituent. Etching of glassware can be a common problem in the dishwasher when aggressive detergents are used and silica levels are sufficient in the water. The early stages of this start with a silica film. This can cause the glasses to be milky colored or even have a rainbow sheen. It is difficult to remove this from glassware and once etching advances, the glassware is damaged beyond repair.

Common Places to See Silica Deposits

Water line in toilet bowl - vary hard build up can only be removed with pumice stone or scraping
On polished chrome surfaces like tub fixtures
Obvious on black porcelain sinks and surfaces as hard white spots, "islands", or spidery networks
Silica domains on glass shower doors - "frosted look"
Dull, white silica build-up on granite counters

The most common attribute of all silica deposits is how hard and stubborn they are. These deposits are very tough and normal calcium scale removers (acids) will not remove silica deposits.

Treatments For Silica In Water

There are only a few ways to reduce silica in the water and most of these are not applicable to residential settings.

1. Lime-soda softening:

This a complex chemical precipitation process using CaOH and Soda Ash to raise the pH to extreme levels causing precipitation of CaCO3 and MgOH. Silica binds to the MgOH and settles out. This method is impractical for residential use.

2. Ultra-filtration:

Specialized polymeric ultra-filters have been developed for industrial water treatment to capture silica. They can be used on colloidal silica but not reactive silica. They are expensive and have not been scaled down for residential use.

3. Anion exchange:

This ion-exchange method can be used for reactive silica, but not colloidal silica. Regeneration of the resins is restricted to industrial applications due to hazardous material handling required.

4. Whole-House Reverse Osmosis:

For residential settings, whole house RO is one way to reduce all types of silica. These systems have to be sized properly and normally pre-treatment for iron & hardness is required.

Because it is so difficult to remove silica from the water, the most common approach to deal with it is one of prevention and mitigation of deposits:

Mitigation of Silica

Lower water temperature below 140 F in dishwashers
Use soft-water detergents with no phosphorus and air-dry only in dishwashers
Wash delicate glassware by hand only
Keep water off of chrome surfaces and glass shower doors to prevent silica spotting
Clean deposits at water line in toilet before they build up using a cleaner like AMAZ or by scrubbing
Use cleaners like AMAZ to clean silica from chrome fixtures and shower doors
Some cleaners with hydrofluoric acid (HF) may help remove silica
Protect glass surfaces using Rain-Ex or other glass coating