Water hardness in Perth
49 mg/L soft
Tap water in Perth is soft: 49 mg/L (2.9 gpg · 2.7 °dH · 4.9 °fH).
Source: Scottish Water — Water Hardness Data 2024 (regulatory supply zones) (2024) · data checked 2026-10-19
Perth is supplied by Scottish Water from surface sources such as lochs and reservoirs fed by upland catchments. The figure is from 2024 data. The calculated hardness (not a direct measurement) is 49.0 mg/L CaCO₃. Rain falling on hard, slow-draining upland rock picks up little calcium, which keeps the water soft; scale is modest in kettles and showers, and most households manage without a softener.
UK suppliers report mg/L CaCO₃ and often Clark degrees (1 °Clark = 14.25 mg/L).
Water data
| Total hardness | 49 mg/L |
|---|---|
| Utility | Scottish Water |
How Perth compares
- Tap water in Perth is 73 % softer than the median of the 471 cities we track in the United Kingdom (185 mg/L).
- By hardness it ranks 394 of 471 in the United Kingdom (1 = hardest); 16 % of these cities have softer water.
- In Scotland it is number 8 of 24 cities; the regional median is 31 mg/L.
- Nearest city with clearly softer water: Carron, 47 km away (32 mg/L).
- Nearest city with clearly harder water: Innerleithen, 89 km away (108 mg/L).
Ranking of the hardest and softest water in the United Kingdom →
What it means at home
- Little or no limescale in kettles, water heaters or washing machines.
- Soap lathers easily; water does not dry skin or hair.
- Dishwasher: salt setting at minimum or off.
- No softener needed; a jug filter only changes taste.
How much salt will you use for softening?
No. Water this soft does not need softening.
Descale a coffee machine or kettle about every 6 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Perth
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 3 °dH |
| AEG / Electrolux | 1 |
| Beko | 1st |
| Hoover | S0 |
| LG | H0 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Perth water hard or soft?
It is soft: 49 mg/L as CaCO₃ (2.9 gpg, 2.7 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Perth safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. UK suppliers report mg/L CaCO₃ and often Clark degrees (1 °Clark = 14.25 mg/L).
How many grains per gallon is Perth water?
2.9 gpg, equal to 2.7 °dH, 4.9 °fH or 49 mg/L calcium carbonate.
What dishwasher salt setting should I use in Perth?
For 49 mg/L (2.7 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Perth?
No. With soft water a softener adds nothing.
Source
Source: Scottish Water — Water Hardness Data 2024 (regulatory supply zones) (2024). Method: computed from supplier's calcium and magnesium. Scottish Water — Water Hardness Data 2024 (regulatory supply zones) · Outdated figure? Tell us