Limescale below the waterline can sometimes be removed entirely by hand but usually, you’ll need a descaling agent.
These fall into three categories: acidic descalers, non-acidic descalers and natural limescale removers (e.g. vinegar and baking soda). These are what you’ll need to completely remove stubborn limescale buildup below the waterline.
Have you ever noticed that your toilet appears considerably dirtier below the waterline? It’s not just you.
The root cause of toilet bowl discolouration below the waterline is limescale. Limescale is a solid – it sinks in water. This often causes heavy limescale buildup at the bottom of the toilet bowl.
Unfortunately, this is one of the trickiest areas of a bathroom to clean!
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What Is Limescale?
Limescale is a hard deposit of calcium carbonate and smaller amounts of iron, manganese and magnesium compounds. From natural aquifers and streams to our water pipes and kettles, limescale occurs everywhere natural water flows.
Limescale concentrations below 500 mg per litre are generally considered not harmful to human health (when consumed). However, even lower concentrations can lead to toilet limescale, particularly at and below the waterline.
According to the Drinking Water Inspectorate, the small governmental department for water regulations in the UK, the “hardness” of water is a measure of calcium carbonate (in milligrams) per litre of water.
Your local water board will be able to provide you with more detailed information regarding water hardness; if you’re unsure who your supplier is, you can check here.
Why Does Limescale Look Brown In Toilets?
If a dirty-looking band of sludge has accumulated in your toilet bowl, just below the water level, you’re probably looking at limescale. Limescale usually has a brownish colour, but it can appear more yellow, brown, black, orange or even blue!
The colour of limescale usually depends on the mineral composition and hardness of the water it’s found in.
In toilets, bacteria and other germs intermingle with the toilet limescale, especially below the waterline. These can give off a foul odour and make the limescale’s appearance considerably worse.
Is Limescale In Toilets Dangerous?
Not immediately. While it won’t put you at risk, limescale can damage toilets and the plumbing they’re connected to, according to the Bathroom Manufacturers Association.
Limescale can block pipes and increase the likelihood of leaks and breaks occurring in toilets. According to British Gas, limescale is also a leading cause of boiler and central heating issues.
Ceramic (otherwise known as porcelain) is the go-to material for bathroom fixtures: it’s used to make practically every bath, wash basin and toilet in the UK.
A glaze is always applied over the top of the raw ceramic. After a quick blast in a very hot furnace, the glaze turns into a tough, glass-like exterior.
Different glazes produce different-coloured finishes but white is by far the most popular choice globally. A toilet’s colour does not affect its ability to resist limescale buildup but discolourations in white toilets can seem worse, due to the contrasting colours.
Removing Limescale Below The Waterline (4 Ways)
No matter which option you choose, you’ll still need to scrub into the toilet bowl to effectively attack stubborn limescale.
Even the most potent limescale removers won’t be able to completely remove limescale below the waterline without some elbow grease.
Don’t use a toilet brush to remove toilet limescale, as the bristles aren’t strong enough and you may accidentally fling toilet water onto yourself during the process.
Additionally, consider wearing hand protection to create a water-proof barrier between your skin and the toilet water.
Kitchen washing-up gloves (colloquially Marigolds) are an excellent choice – they’re durable, reliable, easy to find in shops and cheap, retailing at around £2.00 per pair.
1. Hand Removal
Depending on the severity of the limescale buildup below the waterline, and the general condition of the toilet, you may be able to remove the limescale entirely by hand – no chemicals or cleaning agents necessary.
Scrub-only limescale removal is better suited to ceramic toilets that are: crack-free, chip-free and suffering from light-to-moderate limescale buildup.
Be careful not to scrub with something too abrasive, like a scouring pad or a wire brush, as these could scratch or chip your toilet bowl’s glazed interior finish!
If you own a drill or electric screwdriver, consider investing in a brush attachment. These fit into all common UK drill chucks. They’re usually sold in packs of 5, containing various shapes and sizes of brush.
With the pull of a drill trigger, you’ll be able to scrub away at the limescale buildup in a fraction of the time! Never mix water and electricity – always follow the manufacturer’s instructions.
Avoiding Toilet Damage (Removing Limescale Safely)
To avoid scratching your toilet, attempt to tackle the limescale with gentle scrubbing first.
Try using a softer abrasive (e.g. a sponge or kitchen cloth) first before moving on to harder abrasives (e.g. hard-bristle brushes and scrapers).
The toilet’s glaze is tough but brittle and prone to scrapes. Over time, small scrapes can weaken your toilet’s structural integrity; scrapes allow water to seep into the ceramic beneath the toilet’s exterior coating.
2. Acid-Based Descaling Agents
Many of the most popular toilet limescale removers use acids to chemically react with the limescale, breaking it down into easier-to-flush molecules.
Hydrochloric acid is one of the most effective cleaning chemicals available domestically for this use. It’s found in practically all acidic domestic limescale-removing products to varying degrees.
Hydrochloric acid reacts with calcium carbonate (the main constituent of limestone) to form water, carbon dioxide and calcium chloride.
Strong concentrations of hydrochloric acid can be very dangerous in the wrong hands. This is why you won’t be able to find high-strength hydrochloric acid in descaling products – they’re usually diluted with water, surfactants, fragrances and other liquids to reduce their toxicity.
Acid-based toilet descalers are still highly effective, even when diluted. In the UK, hydrochloric acid concentration can range between 1% to around 22%.
You should wear adequate eye protection and avoid physical contact with strong acids. Keep a window open while using highly-acidic limescale removers and stop immediately if you feel faint, dizzy or fatigued.
If any part of your body does make contact with a strong acidic cleaner (especially the eyes and respiratory system), continually rinse the affected area with fresh water and call for help.
Other acids routinely found in products for removing below-water limescale include: citric acid, phosphoric acid, lactic acid and formic acid.
3. Non-Acid Descaling Agents
Descaling agents that don’t contain synthetic, acidic cleaning chemicals as their main ingredient are often labelled with terms like “Eco”, “Bio-Safe” and “Eco-Friendly”.
They’re considered more environmentally safe as they don’t contain strong acids, which can harm wildlife and humans. Non-acid descaling agents are more expensive than acid-based limescale removers for bathrooms and toilets.
The main ingredients in non-acidic limescale removers are non-ionic surfactants. These act to mix water and oils (e.g. greasy toilet residues) together, similar to an emulsifier.
Non-acidic toilet cleaners may also contain smaller amounts of less harsh acids like formic and lactic acid, perfumes and chemical stabilisers.
4. Vinegar and/or Bicarbonate of Soda
Two “natural” alternatives to normal cleaning chemicals are frequently discussed online: vinegar and baking soda. They’re touted online as effective toilet limescale removers, used individually or combined together.
The main issue arises when they’re used underwater. The toilet bowl water immediately dilutes vinegar, bicarbonate of soda and everything else it comes into contact with.
While vinegar is a strong acid (with a pH of around 2.5), a vinegar-soaked sponge being used underwater will have a pH closer to 6 at its surface. That’s practically neutral!
If you want to properly clean your toilet, leave the vinegar in the kitchen and purchase a proper descaler.
Which Method Is The Best At Removing Underwater Limescale From Toilets?
The most effective cleaning products to remove limescale from toilets below the waterline are acid-based descalers, used alone or in combination with non-acidic descalers.
This isn’t just our opinion. Acid-based limescale-busters are frequently required for cleaning limescale in clinical settings.
Some NHS trusts explicitly require acid-based descalers over alternative products; acids effectively neutralise germs, far better than non-acid-based limescale cleaners.
However, hydrochloric acid must never be used on chrome surfaces – doing so can permanently alter a chrome finish!
Can I Stop Toilet Limescale Permanently?
You won’t be able to absolutely prevent limescale from returning to your toilet in future.
The only failsafe method is extremely expensive: soften the water that enters your toilet, using resin exchangers or electric water softeners. Both of these options would waste an unjustifiable amount of energy.
A few companies claim to manufacture limescale-proof toilets. These are typically standard, ceramic toilets produced with specialist finishings.
The precise science that goes into building toilets that can’t accumulate limescale is usually kept secret. It’s hard to confirm whether these toilets really are immune to limescale buildup or whether these coatings are just clever marketing tactics.
The best way to prevent limescale from returning is to regularly clean your toilet above and below the waterline.