Definition
A logarithmic scale showing whether an aqueous solution is acidic (pH < 7), neutral (pH 7) or basic (pH > 7); the regulatory indicator range for drinking water is 6.5–9.5. In a steam humidifier, low pH increases the corrosion tendency and high pH the scaling tendency.
Detailed Explanation
pH is the negative logarithm of the hydrogen-ion (H⁺) concentration on a 0–14 scale; at 25 °C, pH 7 is neutral. Because the scale is logarithmic, one unit corresponds to a tenfold change in concentration. Measurement uses a temperature-compensated glass-electrode pH meter or colorimetric kits. The Turkish drinking-water regulation and EU Directive 2020/2184 give pH 6.5–9.5 as the indicator range for drinking water.
Why It Matters
Low pH increases the corrosion tendency of the stainless-steel tank and heating elements; if chloride is also high, the risk of pitting corrosion grows. High pH increases calcium-carbonate precipitation and scale build-up. Because carbon dioxide is driven off in boiling water, the pH of the tank water rises above that of the feedwater, so the scaling tendency in the tank is higher than the cold feedwater analysis suggests. RO water readily absorbs carbon dioxide from the air, so its pH is usually slightly below neutral.
Engineering Note
pH is not evaluated alone. The Langelier Saturation Index (LSI) is calculated from pH, calcium hardness, alkalinity, TDS and temperature: a positive LSI indicates a scaling tendency, a negative LSI a tendency to dissolve scale and corrode. Because LSI depends on temperature, a hard water that looks balanced when cold becomes scale-forming at boiling temperature. The acceptable pH range for a humidifier is checked in the manufacturer's feedwater requirements.
How Nem Kontrol Teknolojileri Applies It
As Neptronic's authorised distributor in Türkiye, Nem Kontrol Teknolojileri asks the customer for a recent water analysis from an accredited laboratory when selecting a steam humidifier and compares the values with Neptronic's feedwater requirements. The resistive Neptronic SKE4 runs on any water, RO and DI included; water quality only affects maintenance frequency. Pre-treatment systems are designed and installed by specialist water-treatment companies.
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