Introduction
Tap water in Taiwan generally contains mineral ions such as calcium and magnesium, making it a "hard water" area. The tap water in Shuangbei (Taipei and New Taipei) has particularly high hardness. These calcium and magnesium ions dissolved in the water are prone to chemical reactions when heated or when the water flow is stagnant, forming insoluble precipitates - scale. Over time, scale will gradually clog household pipes, causing water pressure to drop, water heater efficiency to decrease, and even increasing the risk of pipe bursting. This article will completely analyze the formation mechanism, detection methods and prevention strategies of scale from a scientific perspective.
Scale formation mechanism
The main components of scale are calcium carbonate (CaCO₃) and magnesium carbonate (MgCO₃). When calcium ions (Ca²⁺), magnesium ions (Mg²⁺) and bicarbonate (HCO₃⁻) in tap water meet and are heated or the water flow is stagnant, the following reaction will occur:
Ca(HCO₃)₂ → CaCO₃ + CO₂ + H₂O
This type of precipitate will crystallize significantly faster when the water temperature exceeds 60°C, especially in hot water pipes. Studies have pointed out that pipes in hard water areas (calcium and magnesium content >120 mg/L) scale at a rate 3-5 times faster than in soft water areas. In hard water areas such as Banqiao and Zhonghe in Shuangbei, the scale in the pipes can thicken by up to 0.5 mm every year. If the pipes are not cleaned for ten years, the pipe diameter may shrink by more than half.
In addition to carbonate scale, microorganisms such as iron bacteria and algae may also breed in the still water environment. The polysaccharides produced by their metabolism will absorb mineral ions and form a sticky biofilm. Experiments show that the thickness of biofilm in water pipes that have not flowed for 3 months can reach 0.3 mm, and the bacterial content exceeds 10⁴ CFU/cm², of which pathogenic bacteria such as E. coli and Legionella account for 15%. These biofilms further accelerate scale accumulation.
Detection and popular science experiment
How do ordinary people know whether the water pipes in their homes have been scaled? The simplest "acetic acid dissolution method" can help you make a preliminary judgment.
Acetic acid dissolution method
Prepare a cup of white vinegar (acetic acid concentration is about 5%), and soak a section of the detachable faucet aerator or filter in it. If a large number of bubbles appear on the water surface and the solid gradually dissolves, it means that there is calcium carbonate scale on the part. By measuring the weight difference before and after dissolution, the thickness of the scale layer can be estimated.
Influencing factors
The rate of scale formation is affected by many factors:
- Water hardness: The higher the concentration of calcium and magnesium ions, the faster the scale will form.
- Temperature: After exceeding 60°C, the crystallization speed approximately doubles for every 10°C increase.
- pH value: A pH value higher than 7.5 (alkaline) will accelerate the precipitation of calcium carbonate.
- Flow status: Still or slow-moving water is more likely to allow sediment to adhere.
The common "water softener" on the market works by replacing calcium and magnesium ions in the water with sodium ions through ion exchange resin, thereby reducing hardness and scaling. However, the water softener needs to be regenerated regularly, and the treated water has a high sodium content, so it is not recommended to drink it directly.
Preventive science tips
To effectively extend the life of pipelines and avoid the risk of water pressure drop and pipe explosion caused by scaling, the following scientific methods can be adopted:
Regular cleaning
For scaled pipes, physical or chemical cleaning methods can be selected. Physical cleaning such as "pulse cleaning" uses 0.2-0.3 MPa compressed air and water flow to alternately impact, generating a shock wave with a frequency of 15-30 Hz, which can remove 90% of loose scale in 5 minutes. For hard scale with a thickness >3 mm, chemical cleaning with acidic dissolving agents such as citric acid is required.
Anti-scaling technology
- Magnetization treatment: Install a magnetizer in the water inlet pipe to change the crystallization form of calcium and magnesium ions through a magnetic field, making it less likely to adhere to the pipe wall. This is a physical anti-scaling method without adding chemicals.
- Resin water softener: Suitable for areas with persistently high hardness. It can reduce the hardness to below 50 mg/L and reduce scaling from the root.
- Regular circulation: Avoid water pipes standing still for a long time, especially hot water pipes. Turn on the hot water circulation at least once a week to take away the newly formed fine crystals.
Avoid Myths
Many people directly use strong acids (such as hydrochloric acid) when cleaning scale. Although this can quickly dissolve calcium carbonate, it can also corrode metal pipes (especially copper pipes), causing the pipe wall to become thinner or even perforated. It is recommended to use food-grade citric acid (concentration 6-8%), which can dissolve 85% of calcium carbonate scale after reacting at 40°C for 30 minutes, and will cause less damage to the pipe.
In summary, due to the high hardness of tap water in the Shuangbei area, the problem of household pipeline scaling cannot be ignored. Through scientific testing, regular cleaning and appropriate anti-scaling measures, the service life of pipelines can be extended by more than 20 years, while ensuring water safety and equipment efficiency.
Tap water pipeline maintenance and water supply and drainage sanitation and safety standards (2025-2026 Guidelines)
The residential water supply and drainage system is like the blood vessel and metabolic system of the building. According to Taiwan's tap water quality standards and building technical rules for water supply and drainage and sanitary equipment, home water quality and water pressure stability directly affect the water health of the whole family and the lifespan of water equipment. After decades of use, galvanized iron pipes that are common in old apartment buildings in Shuangbei often develop thick rust tumors and biological mud films inside the pipe walls, which not only significantly reduces the water output, but may also release heavy metal impurities, seriously affecting the safety of drinking water.
In terms of hot water systems, old apartments often suffer from insufficient water pressure between floors (dynamic water pressure is less than 0.3 kg/cm²), causing gas water heaters to ignite poorly or bathing to become hot and cold. When installing a pressurizing motor, it is recommended to use a "DC variable frequency constant pressure silent pressurizer" or "electronic flow control pressurizer" with microcomputer chip control to avoid the pipeline water hammer (Water Hammer) effect caused by frequent activation of traditional mechanical pressure switches from damaging old pipe joints. When renovating water supply pipelines, the mainstream industry currently uses SUS304 stainless steel double-crimped coated pipes, which are shock-resistant, temperature-resistant, rust-resistant and corrosion-resistant, and have a service life of more than 30 years.
Key points for daily protection and acceptance of water supply and drainage equipment
- Water meter static leak detection method: When no one in the house is using water and all faucets and toilet inlet valves are closed, observe whether the small red plum blossom pointer in the center of the water meter continues to rotate; if it rotates slightly, it means there is hidden slow seepage in the indoor pipeline or toilet tank.
- Water trap and water seal anti-odor maintenance: There are traps (water seals) inside the bathroom floor drain head and floor drain. If no one uses them for a long time, the isolation effect will be lost due to water evaporation, causing the building's public sewage pipes to cause methane and cockroach pests to enter the room along the pipes. It is recommended to pour 500c.c. of clean water every week to keep the water seal full.
- Regular disassembly and cleaning of the faucet aerator: The aerator filter at the front of the faucet outlet should be removed and cleaned every six months to remove fine sand and calcium carbonate scale deposits carried by the tap water to maintain smooth water flow.
