If you rent, start with what needs no permission: measure your hardness, descale the kettle and showerhead, wipe fixtures dry and follow your appliance manuals. Anything that touches the plumbing, such as a whole-home softener, needs your landlord’s written consent first. Hard water is a nuisance, not a health problem. The USGS describes it as a nuisance and not a health concern.
Step 1: find out how hard it is
Your options depend on the number. Enter your ZIP or postcode on the lookup page, or check your water supplier’s website. The calculator converts units. The USGS classes are soft (0 to 60 mg/L as CaCO₃), moderately hard (61 to 120), hard (121 to 180) and very hard (over 180). One grain per gallon (gpg) is 17.1 mg/L.
In the UK, the Drinking Water Inspectorate (DWI) notes there are no regulatory standards for hardness, and that water at 200 mg/L or more is likely to produce scale. In the US, EPA’s secondary guidance does not list hardness as its own entry either.
| City | Median (mg/L) | Median (gpg) | Class |
|---|---|---|---|
| Houston | 110.0 | 6.4 | Moderately hard |
| Los Angeles | 128.0 | 7.5 | Hard |
| Leeds | 135.6 | 7.9 | Hard |
| Calgary | 199.0 | 11.6 | Very hard |
| Phoenix | 237.0 | 13.9 | Very hard |
| Las Vegas | 280.0 | 16.4 | Very hard |
| Bath | 283.0 | 16.5 | Very hard |
| Southampton | 297.1 | 17.4 | Very hard |
| San Antonio | 299.6 | 17.5 | Very hard |
| Indianapolis | 317.0 | 18.5 | Very hard |
The Phoenix and San Antonio figures are computed from published data. Several cities have a wide range across supply zones, for example Los Angeles at 78.0 to 280.0 mg/L and Indianapolis at 148.0 to 460.0 mg/L. Ask your landlord or the supplier which zone your building is in.
Step 2: options that need no permission
These do not alter the property.
- Descale small appliances. Kettles, coffee machines and irons collect scale first because they heat water. Follow the manual. Our kettle descaling guide shows one manufacturer method.
- Clean fixtures. The USGS notes hard water reacts with soap to form soap scum and needs more soap or detergent. Wiping taps and shower screens dry after use is the cheapest control.
- Adjust appliance settings. If your dishwasher or coffee machine has a hardness setting, set it to your figure. See the dishwasher salt guide.
- Use less cleaner and detergent where your manual allows. Hard water needs more soap to lather, and that applies to laundry too. Follow the detergent label.
Step 3: options that may need permission
Check your tenancy agreement first. Government guidance for tenants in England says to get your landlord’s permission before attempting repairs or decorating, and the same cautious approach applies to any plumbing change. We found no general rule that covers appliances, so the agreement and your landlord decide.
| Option | What it involves | Permission usually needed |
|---|---|---|
| Showerhead or tap attachment | Screws on, removable | Check the agreement |
| Point-of-use cartridge on one tap | Small fitting under a sink | Yes, if it alters plumbing |
| Whole-home softener or conditioner | Cut into the main supply, drain, power, space | Yes, in writing |
| Appliance with its own softening unit | A dishwasher or washing machine with a built-in unit | Only if it replaces a landlord’s appliance |
About filters and cartridges. Many shower filters are sold to reduce chlorine or sediment. Removing hardness needs a different process, such as ion exchange. We have no independent test data that rates tenant-fit devices, so we give no performance figures. Read what the product says it removes.
If you ask for a softener
A softener is a landlord decision because it becomes part of the building. If you raise it, bring facts:
- Your hardness figure and its source.
- Which appliances or fixtures are affected.
- Who would own it, who pays for salt and servicing, and what happens when you move out. Put this in writing.
Two cautions come from the DWI. First, softening by base exchange adds sodium, so keep an unsoftened tap for drinking and cooking. The DWI mentions this matters for premature babies and people on low-sodium diets. Second, softened water can increase copper and lead leaching from plumbing. If the building has older pipes, ask for advice before installing. If you have a medical question, speak to a clinician. This is general information, not medical advice.
The DWI also suggests a minimum hardness of 150 mg/L where water companies soften. That is a supplier guideline, not a rule for homes.
Moving: use hardness as a checklist item
If you are choosing a new rental, look up the hardness for the address before you sign. A very hard area (over 180 mg/L) means more cleaning and more appliance maintenance, but it is not a reason to avoid a place on health grounds. Ask whether the building has a water heater that is easy to flush, and whether the landlord is open to a softener.
FAQ
Can my landlord refuse a softener? Yes, in most cases. It alters the plumbing and the property, so it is the landlord’s decision unless your agreement says otherwise. Ask in writing and offer to cover running costs.
Is hard water harmful to drink? The DWI says there is only limited evidence of a relationship between hardness and cardiovascular health, and it is possibly beneficial through calcium and magnesium. The main problems are scale and soap use. If you have a health question, ask a clinician.
Will a descaled kettle fix my water? No. It removes scale from one appliance. It does not change the water. It is still the first step, because kettles show the problem soonest.
Sources
- USGS, Water Science School, Hardness of water: https://www.usgs.gov/special-topics/water-science-school/science/hardness-water
- Drinking Water Inspectorate, Water hardness / hard water: https://www.dwi.gov.uk/consumers/learn-more-about-your-water/water-hardness-hard-water/
- GOV.UK, How to rent: the checklist for renting in England: https://www.gov.uk/government/publications/how-to-rent/how-to-rent-the-checklist-for-renting-in-england
- City figures: source pages linked from each city page above.