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How to use a glass water filter jug

Updated: 23 October 2026

The first week is where a glass filter jug goes wrong. You drink the priming water, you leave the cartridge in for months, or you leave filtered water on a warm worktop until a film appears. A carbon cartridge takes much of the chlorine taste away, and a warm jug is then an easier place for slime. This page is the routine for a gravity glass jug: flush, keep it cold, change on the earlier limit, and know what the black specks are. The steps follow the BRITA 2026 jug instructions, the Water UK home leaflet and the listings in our 19 October 2026 capture. This is not a hygiene test. Ranking stays on the [filter glass comparison](/hub/diy-supplies/filter-glass).

The first week is where a glass filter jug goes wrong. You drink the priming water, you leave the cartridge in for months, or you leave filtered water on a warm worktop until a film appears.

Our top picks

BRITA BRITA glass filter jug

Best overall

BRITA BRITA glass filter jug
8.6/10about £47.49
View offer
AQUAPHOR AQUAPHOR white glass jug

Best value

AQUAPHOR AQUAPHOR white glass jug
8.4/10about £34.99
View offer
Aarke Aarke Purifier Large

Alternative

Aarke Aarke Purifier Large
8.2/10about £119.98
View offer
On this page
  1. 1.Before the first glass
  2. 2.Cold water, fridge, 24 hours
  3. 3.When to change the cartridge
  4. 4.Mould, slime, and black specks
  5. 5.Boil notices and when this page stops

Before the first glass

Wash the jug with washing-up liquid and rinse it before the cartridge goes in. BRITA’s 2026 instructions say cold mains water only, then two full funnels through a new MAXTRA PRO cartridge before you drink. That first water is the flush. Do not start with hot water from the kettle. If you have an Aarke, reviews describe a metallic taste until about 2 litres have been run through. That figure is from reviews of the Purifier Large, not from the BRITA leaflet, so do not paste one flush onto the other jug. Follow the leaflet in the Aquaphor box, and treat its counter as a reminder, not as proof the water is ready. A split or crushed cartridge should not go into service. Water UK’s advice on a damaged cartridge is to change it.

Cold water, fridge, 24 hours

Fill from the cold tap. BRITA and Water UK both say filtered jug water should stay cool and be drunk within 24 hours. The fridge is the simple place, if the jug fits. The 24-hour limit is about water you have already filtered. Pouring it back through the top does not reset the cartridge. If the jug misses the door shelf, a warm worktop shortens the time you should trust the water. Which body is worth buying is on the buying guide.
BRITA BRITA glass filter jug

Testsieger

BRITA BRITA glass filter jug
8.6/10about £47.49
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When to change the cartridge

The week limit wins even when litres remain. BRITA sets MAXTRA PRO at 150 litres or four weeks, whichever comes first, and sooner in harder water. This page does not convert German degrees. Use your water company’s figure, and the hard water page. Aquaphor says up to 200 litres or 60 days. The PT-72 says two months. The Aarke granules are four weeks. A light user hits the weeks before the litres. If the indicator disagrees with the date you wrote down, believe the earlier date.

Mould, slime, and black specks

A warm jug grows a film because the cartridge has reduced the chlorine that was holding microbes back. Wash the jug, throw the water away, fit a new cartridge, and dry the lid before it goes back in the fridge. Black specks are often carbon fines, which Water UK describes as particles from the cartridge, not a failed tap. Flush again. A chipped spout does not rinse out. BRITA’s bullets allow the dishwasher up to 60°C except the Smart Light and the silicone ring. Aquaphor excludes the lid and the funnel. Follow the listing you bought.

Boil notices and when this page stops

If your water company issues a boil notice, BRITA’s instruction is to filter first and then boil. The jug is not a substitute for the boil. If the notice says do not drink the water, use the supply the company tells you to use. A slimy jug is a washing job. A leak onto the electrics of an ED12W or an M6HG is not: unplug it. Pipework, a private supply, and a plumbed reverse-osmosis unit are outside this routine. Tell the water company before a plumbed install. If you do not own a jug yet, the short list is on the best glass water filter jug page.

Common questions

Do you drink the first fill?
No. BRITA’s 2026 instructions say two full funnels of cold mains water through a new MAXTRA PRO cartridge before you drink. That water is the flush. Aarke reviews describe a metallic taste until about 2 litres have been run through. That 2 litre figure is a review report, not the BRITA step, so match the flush to the jug you own.
Can you use hot water?
Use cold mains water. BRITA’s instruction file says cold water only. Filling from the kettle to hurry the cartridge along is outside that leaflet, and it is a poor way to start a carbon filter. If a boil notice is in force, you still filter cold and then boil the filtered water, rather than pouring boiling water into the funnel.
Is it four weeks or 150 litres?
For a MAXTRA PRO cartridge it is whichever comes first. BRITA states 150 litres or four weeks. A household that drinks little water will hit the weeks while litres remain, and the week limit still applies. Aquaphor’s glass listing says up to 200 litres or 60 days. The PT-72 says two months. The Aarke granules are four weeks. Write the date on the day you fit it.
What are the black bits?
Water UK describes small black particles from a carbon cartridge as carbon fines. Flush the jug again. They are not, by themselves, evidence that the mains supply has failed. If the cartridge is split, or the specks keep coming, change the cartridge. A chip in the glass spout is a separate fault and is not carbon.
Which parts are dishwasher safe?
It depends on the listing. BRITA’s bullets allow the dishwasher up to 60°C except the Smart Light and the silicone ring. Aquaphor’s bullets exclude the lid and the funnel. Aarke’s bullets say the steel cartridge is dishwasher safe. The BRITA specification also prints an upper temperature of 100°C, which does not match the 60°C bullet, so follow the more cautious line until the leaflet in your box says otherwise.

Related pages

Jug or reverse osmosis

Filter glass

Best glass water filter jug UK: a review-count rule

Glass water filter jug buying guide: check the job

Glass water filter jug for hard water kettle scale

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Updated 22.10.2026.

  1. DWI: domestic water filters and softeners (retrieved 22.10.2026)
  2. DWI: water hardness (retrieved 22.10.2026)
  3. DWI: chlorine (retrieved 22.10.2026)
  4. DWI: PFAS and forever chemicals (retrieved 22.10.2026)
  5. Water UK: Looking after water in your home (retrieved 22.10.2026)
  6. Water fittings regulation 4 (retrieved 22.10.2026)
  7. NSF: NSF/ANSI 42, 53 and 401 (retrieved 22.10.2026)
  8. BRITA jug instructions (2026 PDF) (retrieved 22.10.2026)
  9. Which?: water filter jugs (retrieved 22.10.2026)