Glass water filter jug for hard water
Updated: 23 October 2026
The kettle fur is back a week after you descaled it, and a glass jug is being sold as if it softened the house. In a hard part of England or Wales, a glass water filter jug can mean less scum on tea and a thinner film in the kettle. It does not turn a hard supply soft. Ion-exchange resin can lower temporary hardness only while it is still working. Permanent hardness stays. Figures are from the Drinking Water Inspectorate and amazon.co.uk listings captured on 19 October 2026. A qualifying purchase can earn us a commission at no extra cost to you. The rows are on the [filter glass comparison](/hub/diy-supplies/filter-glass).
The kettle fur is back a week after you descaled it, and a glass jug is being sold as if it softened the house.
The kettle fur is back a week after you descaled it, and a glass jug is being sold as if it softened the house. In a hard part of England or Wales, a glass water filter jug can mean less scum on tea and a thinner film in the kettle. It does not turn a hard supply soft. Ion-exchange resin can lower temporary hardness only while it is still working. Permanent hardness stays. Figures are from the Drinking Water Inspectorate and amazon.co.uk listings captured on 19 October 2026. A qualifying purchase can earn us a commission at no extra cost to you. The rows are on the filter glass comparison.
Our top picks
| Badge | Product | Filtration | Cartridge life | TDS note | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Waterdrop Waterdrop PT-72 white jug | Carbon and ion exchange | 2 months or up to 100 gallons | Does not lower TDS | 9.2 | about £39.99 | View offer |
 BRITA BRITA glass filter jug | Carbon and ion exchange; limescale named | 4 weeks or 150 L | n/a; max 300 ppm | 8.6 | about £47.49 | View offer | |
| Best value |  AQUAPHOR AQUAPHOR white glass jug | Activated carbon; limescale named | 60 days or up to 200 L | n/a | 8.4 | about £34.99 | View offer |
On this page
Hard, in numbers
Hardness on a UK report is milligrams per litre as calcium carbonate. The Drinking Water Inspectorate’s scale runs from soft, up to 100 mg/l, to very hard, above 300 mg/l. Your water company’s postcode report is the figure that matters. There is no regulatory limit for hardness. It is a nuisance, not a pass or fail. London and the South East are often spoken of as hard. That is not a measurement of your street. Dŵr Cymru explains the split: temporary hardness drops out when you boil, which is the scale on the element, and permanent hardness stays dissolved. German degrees on a cartridge FAQ are not this scale. Do not convert them at the kitchen table.
What a jug changes
What changes is temporary hardness in the water you pour through a fresh ion-exchange cartridge. The Inspectorate’s description is practical: less tea scum, and some reduction in kettle scale, for as long as the resin has capacity. BRITA’s bullets name limescale and ion-exchange pearls, and the cartridge is listed for 150 litres or four weeks, whichever comes first. In harder water that volume is used up sooner. Scale returning before the calendar date means the resin is spent. Carbon on its own is a taste filter. If the listing does not mention ion exchange or limescale, do not expect the fur to slow down. Changing on time is on how to use a glass water filter jug.
What it does not change
A jug does not remove permanent hardness, and it does not soften the rest of the house. The shower, the boiler and the washing machine never see the cartridge. A base-exchange softener swaps calcium and magnesium for sodium, and the Drinking Water Inspectorate says you should keep an unsoftened kitchen tap. Artificially softened water from that softener is not for baby formula, because of the sodium. That warning belongs to the softener. This capture does not print a sodium figure for MAXTRA PRO, so it is not pinned on the BRITA glass jug. A cleaner kettle, for a few weeks at a time, is the result the sources support. A whole-house change is a softener and a separate drinking tap, not a 2.5 litre jug.
Listings in this capture that name scale or ion exchange
The BRITA glass jug names limescale and ion-exchange pearls, with no statement that TDS falls. Both PT-72 colours name ion-exchange resin and also say the jug does not lower TDS. You can still get less kettle film while a dissolved-solids pen barely moves. Aquaphor’s bullets name limescale without an NSF number. The M6HG is reverse osmosis and leaves this page. The review-count rule is on the best glass water filter jug page.
When the jug is the wrong tool
The jug is the wrong tool when the goal is the whole supply, when permanent hardness is what you measured, or when you want the TDS number itself to fall. For the kettle and the tea, a cartridge that names ion exchange is the proportionate buy, and you replace it when the scale returns or the time limit arrives, whichever is sooner. Dissolved solids are a different job, with a waste stream. A softener is the whole-house option only with an unsoftened drinking tap. Neither a jug nor a countertop filter replaces a water-company investigation if you suspect lead pipework or a microbiological fault.
Common questions
What is temporary hardness?
Temporary hardness is the carbonate part of the calcium and magnesium in the water. Dŵr Cymru’s explanation is the kitchen one: it drops out when you boil, which is the white film on the element. Permanent hardness does not drop out on boiling and stays dissolved. A jug with fresh ion-exchange resin is aimed at the temporary part only.
What number counts as hard?
The Drinking Water Inspectorate treats water as soft up to 100 mg/l as calcium carbonate and very hard above 300 mg/l. Your water company’s postcode report gives the number for your supply, in those units. There is no legal limit. A regional reputation, including the South East, does not replace that report.
Does the jug remove permanent hardness?
No. The Inspectorate says jug filters with ion-exchange resin do not remove permanent hardness. Boiling does not remove it either. If a test or your company’s report is mostly permanent hardness, a jug will not produce the change you are picturing in the kettle, because that fraction was never going to fall out as scale in the same way.
Is a jug a water softener?
No. A base-exchange softener treats water for the appliances downstream and adds sodium. You keep a kitchen tap on the unsoftened supply. The Inspectorate’s warning that artificially softened water is not for baby formula belongs to that softener, not to a filter jug. A jug only treats the water you pour through it.
Why can TDS stay high after a jug in a hard area?
A TDS meter adds up dissolved material. The PT-72 bullets say that jug does not lower TDS, even though they also name ion-exchange resin. Temporary hardness can ease in the kettle while the meter barely moves, because the meter was never a kettle-scale gauge. Judging a carbon jug by a TDS pen is the wrong test.
Related pages
Sources
Public UK sources and the amazon.co.uk listings compared on this page. Updated 22.10.2026.
- DWI: domestic water filters and softeners (retrieved 22.10.2026)
- DWI: water hardness (retrieved 22.10.2026)
- DWI: chlorine (retrieved 22.10.2026)
- DWI: PFAS and forever chemicals (retrieved 22.10.2026)
- Water UK: Looking after water in your home (retrieved 22.10.2026)
- Water fittings regulation 4 (retrieved 22.10.2026)
- NSF: NSF/ANSI 42, 53 and 401 (retrieved 22.10.2026)
- BRITA jug instructions (2026 PDF) (retrieved 22.10.2026)
- Which?: water filter jugs (retrieved 22.10.2026)