What is limescale?
Limescale, also known as hard water buildup, refers to the chalky white mineral deposits that can accumulate inside pipes, on bathroom and kitchen surfaces and on appliances that use water. It’s composed mainly of calcium carbonate and magnesium carbonate.
Limescale is formed when hard water evaporates and leaves behind the minerals that were dissolved in it. Hard water contains high concentrations of calcium and magnesium ions, which come from rocks and sediments that the water has passed through.
When hard water is heated or exposed to air, the dissolved calcium and magnesium precipitate out of the water, leaving behind limescale on any surfaces the water is touching. The warmer the water is, the more minerals come out of solution and the more limescale forms.
Where does limescale come from?
The main sources of limescale are:
– Hard groundwater – Water that has percolated down through limestone, chalk or gypsum deposits will be rich in dissolved calcium and magnesium and become hard water. This is the most common cause of limescale.
– Water pipes – Old metal water pipes can corrode over time and release iron, zinc, manganese and other minerals into the water, contributing to limescale formation.
– Water heaters – As water is heated inside a water heater tank, limescale rapidly precipitates out. Water heaters are often major sites of limescale accumulation.
– Appliances – Any appliance that evaporates, heats or airs hard water can be prone to limescale, including kettles, coffee makers, steam irons, ice makers and more. Evaporation leaves deposits behind.
So in summary, limescale comes from dissolved mineral ions in hard water. Heating and evaporation cause them to precipitate out as solid deposits.
Is limescale permanent?
Limescale deposits are not permanent features. Although they can be extremely hard and difficult to remove once formed, they can be dissolved, descaled and removed with the right techniques and products. However, if left untreated in pipes and appliances, limescale accumulation will continue worsening over time.
Some factors that determine whether limescale is easily removable or more permanent include:
Age of the limescale
The longer limescale has been accumulating, the thicker and more cemented on it will become. Older limescale is harder to descale.
Temperature
Limescale from hot water heaters and boilers that form in very hot, pressurized systems can be denser and more tightly bonded.
Water flow
Areas with turbulent water flow, like pipe elbows and junctions, develop thicker limescale deposits. Stagnant water allows limescale to solidify.
Water chemistry
The makeup of dissolved solids can impact limescale strength. High magnesium tends to make sturdier deposits.
Surfaces
Non-stick and smooth surfaces like plastic and glass accumulate less stubborn limescale than rough surfaces like stainless steel or concrete.
So while limescale is not technically a permanent fixture, the longer it builds up the more difficult it is to remove. A light coating that is promptly descaled will not be very stubborn, but thick accumulations especially in hot water systems or on rough surfaces can be cement-like.
How can limescale be prevented and removed?
There are several approaches to preventing and removing limescale:
Preventing limescale
– Use water softening to remove calcium and magnesium ions from hard water through ion exchange. This prevents limescale from forming.
– Install magnetic/electronic water conditioners. These can transform dissolved minerals to prevent limescale precipitation.
– Use a reverse osmosis system to filter out minerals from water.
– Acidify water with citric acid or vinegar to prevent mineral precipitation.
Removing existing limescale
– Chemical cleaners – Products containing acids such as phosphoric, hydrochloric, sulfamic and citric acid dissolve limescale.
– Descalers – These electric devices use ions, magnets or catalysts to dissolve existing limescale.
– Mechanical removal – Scrubbing, pressure washing, sanding or scraping to physically remove deposits.
– Electrochemical devices – Apply a low voltage electric signal to electrodes in water to dissolve minerals.
– Water softeners – Soften hard water to stop further buildup and then clean pipes and appliances to remove old scale.
What are the effects of limescale?
Some common effects of limescale buildup include:
Reduced flow
Limescale deposits narrow pipes and reduce water flow through plumbing. Showers, taps and appliances get lower water pressure.
Loss of efficiency
Appliances like electric kettles and hot water heaters become less energy efficient with limescale coating the heating elements. More energy is required to heat the water.
Overheating
The limescale coating acts as an insulator that retains more heat. As a result, water heaters and other appliances can overheat, fail faster and become fire hazards.
Corrosion damage
Limescale deposits roughen surfaces and promote corrosion of pipes, fittings and appliances. Pitting and leaks can develop.
Pipe clogs
Loose limescale chunks and overgrowths can completely clog water pipes, causing low pressure and flow interruptions.
Staining
Hard water staining appears on everything it contacts – faucets, shower doors, counters, dishes, clothing and more. Limescale etches into the surfaces.
Is limescale harmful to human health?
Limescale itself is generally not considered harmful to human health. The minerals calcium and magnesium that make up limescale are actually essential nutrients, and calcium is needed for healthy bones and teeth.
However, limescale can indirectly cause some health issues:
– Scale buildup inside water pipes can provide places for bacteria like legionella to grow and multiply. This bacteria causes Legionnaires’ disease which can be fatal.
– Loss of water pressure and flow can make hand washing and bathing more difficult. Poor hygiene increases risk of infections.
– Overheating appliances pose a burn or fire hazard. Fires produce toxic fumes that are hazardous if inhaled.
– Corroded pipes and fittings can leach lead, copper and other metals into drinking water in small amounts. Ingesting these heavy metals is unhealthy.
So while limescale itself is not toxic, problems associated with severe limescale buildup can potentially impact human health and safety. Maintaining clear plumbing and descaling appliances is important.
Can limescale return after removal?
If the underlying cause of limescale is not addressed, then yes, limescale will return again after removal. Hard water will continue to produce limescale deposits unless it is softened or conditioned.
Some steps to prevent limescale returning after descaling include:
– Install a water softener or conditioner to remove calcium and magnesium minerals from the water supply. This stops the limescale at the source.
– Use a chemical descaler regularly. Cleaners containing acids dissolve any new limescale before it sticks and builds up a hard deposit.
– Replace metal pipes and fittings with plastic. Plastic plumbing resists limescale sticking to it.
– Upgrade to more efficient water heater and appliances. Modern tankless heaters allow less limescale to form.
– Insulate hot water pipes. This reduces heat loss so water stays hot but does not overheat. Lower temperature means less limescale.
– Flush out pipes thoroughly after descaling. This removes any loose scale so it cannot re-solidify and cement on pipes.
With diligent water conditioning and regular descaling, limescale can be kept under control even in very hard water areas. Though not permanent, limescale has a tendency to quickly return and spread if hard water conditions are not resolved.
Conclusion
While limescale deposits are not technically permanent fixtures, they can become extremely stubborn and difficult to remove if allowed to build up over time, especially in hot water systems. Hard water provides an endless supply of dissolved calcium and magnesium minerals which then solidify as limescale on surfaces and inside pipes and appliances.
Prevention is key to avoiding limescale becoming near-permanent. Water softeners, ion exchangers, reverse osmosis, acid dosing and upgrading appliances all help limit limescale formation. For existing scale, chemical descalers, mechanical scrubbing and electrochemical devices can all help remove deposits, though thorough removal becomes more challenging the longer limescale has accumulated.
Limescale causes a variety of problems, from reduced water flow and staining to appliance damage and increased bacterial growth. Though not directly harmful to health, severe limescale can lead to unsafe conditions. After descaling, steps must be taken to prevent limescale returning again if hard water conditions persist. With proper prevention and removal techniques, limescale does not have to be a permanent problem.