Setting Up Dishwasher’s Water Hardness Settings
Dishwashers need to be calibrated for local water hardness. Most work adequately on factory defaults, but in hard water areas incorrect settings cause limescale and poor wash results, while in soft water areas the machine may use excess salt. Check the instruction manual for the specific adjustment procedure for your model.
Unlike washing machines, dishwashers need to be set up for the local water hardness level. Factory default settings aim to suit average UK conditions, but water hardness varies significantly from area to area. A dishwasher set for hard water in a soft water area – or vice versa – will not perform as well as it should.
Why Water Hardness Settings Matter
Most dishwashers operate adequately without being calibrated for local water hardness, and owners may not notice any issue. However, problems can become apparent at the extremes:
- In a very hard water area, incorrect settings can cause poor wash results and limescale build-up inside the machine.
- In a very soft water area, the machine may use more salt than necessary, or excessive foaming can occur.
- When using all-in-one multi-tab detergent in a soft water area, it may be possible to stop using rinse aid altogether and save money.
How to Set Up a Dishwasher for Water Hardness
The exact procedure varies between models and manufacturers, so the instruction manual must be consulted. If the original manual is not available, it may be possible to download one via the manufacturer’s website – links to manufacturer manual pages can be found at: instruction books and user manuals.
The Two Typical Adjustments
Many dishwashers have two separate water hardness adjustments that work together:
1. A physical dial or switch – typically located on the lower inner panel of the door, usually just above the salt compartment. This commonly offers two positions (for example, 1 and 2), with the default factory setting at the higher (hard water) position. In a soft water area this can be turned down to the lower setting.
2. An electronic setting – accessed through a button combination that puts the dishwasher into a programming mode, allowing selection from a range of levels (often 1 to 10) corresponding to water hardness ranges listed in a chart in the instruction manual. At the lowest setting, many manuals specify that no salt is needed at all. The exact method varies by model – check the instruction manual for the specific procedure.
There is no universal procedure to describe here as every dishwasher model is different. The instruction manual is the definitive source.
Using Multi-Tab or All-in-One Detergent
If using multi-tab or all-in-one detergent tablets, these are designed to replace separate salt and rinse aid, so the water hardness adjustments described above may not be necessary. However, the dishwasher must still be set up to recognise that this type of detergent is being used – otherwise it may continue attempting to dispense salt and rinse aid in addition to the tablet. See: have you calibrated your dishwasher for multi-tab detergent?
In real-world use, multi-tab detergent does not always fully replace the need for rinse aid – results vary by brand, tablet quality, and local water hardness. In moderately hard water areas in particular, some residual water may collect in the tops of mugs or small indentations on dishes even when using all-in-one tablets. Reintroducing a small amount of rinse aid – with the dispenser set to the minimum dose – can resolve this while still reducing overall rinse aid consumption significantly compared to using standard detergent. In genuinely soft water areas, multi-tab detergent alone is more likely to be fully sufficient. Experimenting with settings based on local water hardness and the specific brand of tablet used is the best approach.
How to Find Out Local Water Hardness
Water hardness information is available from local water suppliers. Most publish this on their websites. A list of water company contact details is available from Ofwat (the water services regulator).
Dishwasher Detergent Tests and Reviews
Which? has tested dishwasher detergents across a range of brands and types. Results vary considerably between products.
Related dishwasher guides
Frequently Asked Questions
Do I need to adjust my dishwasher for water hardness?
Most dishwashers will work adequately without adjustment, but performance may not be optimal. In hard water areas, incorrect settings can cause limescale build-up and poor wash results. In soft water areas, the machine may use more salt than needed or produce excess foaming. Checking and setting the water hardness level according to the instruction manual is good practice, particularly if wash results are disappointing.
Do I still need to use salt and rinse aid if I use multi-tab detergent?
Multi-tab tablets are designed to replace separate salt and rinse aid. In soft water areas, they often work well alone. In moderately hard or hard water areas, some residual water spots or pooling may still occur even with quality multi-tab tablets – in which case adding a small amount of rinse aid at the minimum dispenser setting can help. The dishwasher also needs to be calibrated to know it is using multi-tab detergent. See: calibrating for multi-tab detergent.
How do I find out how hard the water is in my area?
Check with your local water supplier – most publish water hardness data on their websites. A list of water company contact details can be found via Ofwat.
Where can I find the instruction manual for my dishwasher?
If the original manual is not available, most manufacturers make manuals available for download on their websites. Links to manufacturer manual download pages can be found at: instruction books and user manuals.