If you see a cloudy white film on your dishes after washing, cloudy glass, or a bad odor from the machine, the number one "suspect" is hard water. Most areas in Vietnam have moderate to high levels of hard water. This article explains what hard water is, its harmful effects on dishwashers, and how to effectively treat it.
1. What is hard water?
Hard water is water that contains a high concentration of Calcium (Ca²⁺) and Magnesium (Mg²⁺) ions, typically measured in mg/l or °dH (degrees of German hardness).
| Classification | °dH | mg/l CaCO₃ |
|---|---|---|
| Soft water | 0-7 | 0-125 |
| Medium | 7-14 | 125-250 |
| Moderately hard | 14-21 | 250-375 |
| Very hard | >21 | >375 |
2. Hard water situation in Vietnam
- Hanoi: many areas have moderately hard water (12-18 °dH), especially areas using groundwater.
- Ho Chi Minh City: tap water is generally medium (8-12 °dH), but many areas using boreholes have high hardness.
- Limestone areas (Ninh Binh, Hoa Binh, Quang Binh, Da Nang...): water is often very hard (>20 °dH).
In summary: almost all dishwashers in Vietnam need water softening.
3. Harmful effects of hard water on dishwashers
3.1. Damages the heating element
When hard water is heated, Ca/Mg precipitates into limescale that adheres to the heating element. After a few months, the thick layer of scale prevents the heating element from dissipating heat → reduced efficiency, increased power consumption, and potential heating element burnout.
3.2. Reduces washing effectiveness
Ca/Mg ions "lock" enzymes and detergents in dishwasher tablets → tablets cannot perform at their full potential. This is why many people complain, "I bought expensive tablets, but they still don't clean well."
3.3. Makes glass cloudy
The white stains that cling to glass after drying are limescale. Wash them off, and they reappear after a few days. Over time, the glass will be permanently etched (cloudy in quality).
3.4. Clogs spray arms
The spray holes are small, and limescale easily builds up → water does not spray evenly, dishes are not cleaned thoroughly.
3.5. Machine smells musty
Limescale buildup inside the machine creates an environment for anaerobic bacteria to grow, causing a distinctive musty odor.
4. Some signs that your machine is "crying for help"
- Dishes have a cloudy white film after drying.
- Glassware loses its shine.
- Washing with tablets is not as effective as before.
- Washing time is longer, and the machine is louder.
- Unpleasant odor when opening the machine.
- "Salt" or "Refill salt" warning light is on.
5. Solution: Integrated water softening system
All modern dishwashers have an internal ion-exchange resin tank. This resin absorbs Ca/Mg and replaces it with Na (sodium) → soft water. When the resin is "saturated," specialized salt is needed to regenerate it.
Regular salt (table salt, sea salt) cannot be used because it contains impurities that will damage the system.
Largo specialized dishwasher salt is particularly suitable:
- >99.9% pure NaCl.
- Large granules, slow-dissolving, non-caking.
- Directly imported from Germany.
- 2kg pack → sufficient for ~2-3 months for a family of 4.
→ Order now: Largo German Dishwasher Salt 2kg – 175,000đ
6. How to correctly add salt
- Open the dishwasher door, pull out the bottom rack.
- Unscrew the cap at the bottom of the machine (marked with a salt star symbol, usually near the filter).
- First time: pour 1L of filtered water into the reservoir. Then add Largo salt until full.
- Subsequent times: only add salt when the warning light comes on.
- Tighten the cap securely to prevent water from spilling.
7. Refill frequency
On average, add salt once every 2-3 months (for a family of 4-5 people). If the water in your area is very hard, it might be 1.5 months / time.
8. Comprehensive treatment strategy
Salt only addresses the hard water problem. To prevent limescale spots on dishes after washing, you also need rinse aid. Combined with dishwasher tablets, you will have a complete trio.
Most economical solution: Largo Trio Combo – 555,000đ (save 38,000đ).
9. Conclusion
Hard water is an invisible problem with very clear consequences: unclean dishes, cloudy glassware, and premature machine damage. Adding enough specialized Largo salt is not optional – it is a mandatory condition for your dishwasher to remain durable and operate at peak performance.