Bosch fridge water filters

Bosch's American style fridges use the UltraClarity filter system, the same platform shared with sister brand Siemens under parent company BSH. The reference is the same on both brands.

How to identify your Bosch fridge

Bosch prints the full appliance model number, starting with a letter such as B, on a rating plate inside the fridge compartment, usually on the side wall.

The UltraClarity cartridge sits in a dedicated internal housing; if your Bosch fridge has no such housing, it may use an external filter on the water line instead and this page does not apply to it.

Water filters for Bosch fridges

Each reference below has its own page on this site with the full list of fridges it fits, the fitting steps and the mistakes that send people back to buy a second cartridge.

Filter reference	Fitting position	Change interval
644845 (UltraClarity)	Internal cartridge, UltraClarity housing system	Every 6 months

Where Bosch owners go wrong

Confusing the UltraClarity cartridge with a generic inline filter bought for a different brand: the UltraClarity housing is a twist fit specific to the Bosch and Siemens platform.
Not checking that your specific Bosch range actually has an internal filter housing before ordering, since not every Bosch fridge sold in the UK is fitted with one.

When to change the filter

Bosch recommends a cartridge change roughly every six months, in line with the wider UltraClarity platform used across Bosch and Siemens fridges.

Bosch water filters: common questions

Does the Bosch UltraClarity cartridge fit a Siemens fridge too?

Yes. Bosch and Siemens fridges share the same parent company, BSH, and the same UltraClarity filter platform, so the reference on this site's model page applies to both brands.

See current Bosch water filter prices on Amazon UK

Tools, access space and quantities to prepare

You do not normally need a spanner for an internal Bosch UltraClarity cartridge. The useful items are a dry cloth, a shallow bowl, a torch, and a jug for flushing water after fitting. Allow about 10 minutes for a straightforward change, plus the time needed to run water through the dispenser.

Item or figure	Practical value	Why it matters
Working clearance in front of the fridge	About 60 cm	Enough room to open the door fully and stand square to the filter housing.
Clearance around the internal housing	About 10 to 15 cm	Enough space for your hand to grip and turn the cartridge without forcing the plastic parts.
Water to catch during removal	Usually a few teaspoons, prepare for 100 ml	A cloth and shallow bowl prevent water from running into shelves or the door seal channel.
Flush volume after fitting	About 3 to 5 litres	This clears trapped air and fine carbon dust before normal use.
Typical job time	10 to 20 minutes	Includes removal, fitting, leak check and flushing.

If the cartridge is above a shelf, remove bottles and tall items first. Do not try to work round glass containers or heavy food. A slipping cartridge can hit the shelf edge and crack plastic trim. If the fridge door has a water dispenser, place a jug that holds at least 1 litre under the outlet so you can flush in several controlled fills.

Step by step filter change procedure

Start with clean, dry hands. Open the fridge door fully and look directly at the filter head. Note the position of any mark, arrow or locked position before turning the old cartridge. This gives you a reference when fitting the new one.

Place a cloth under the housing and keep a shallow bowl close by.
Grip the old cartridge body, not the thin edge of the cap or label area.
Turn the cartridge steadily to the release position. Do not jerk it. A quarter turn is common on this type of internal cartridge, but follow the marks on the housing if they differ.
Pull the cartridge straight out along its own axis. If it resists, turn it back slightly and try again rather than levering it sideways.
Check the filter head for broken plastic, dirt, or an old sealing ring left behind. Do not insert the new cartridge if the port is obstructed.
Insert the new cartridge squarely and push it in until it seats. Turn it to the locked position using firm hand pressure only.
Close the door gently, dispense water, then stop and inspect the housing with a torch.
Flush about 3 to 5 litres of water through the dispenser in batches. Short pauses help trapped air move out of the system.

If your fridge has a filter reset function, reset it only after the cartridge is fitted and checked for leaks. The reset is a reminder counter, not a water quality test. If you need the cartridge page with fitting notes, use Bosch Siemens 644845.

Frequent faults during fitting and how to recover

A slow drip immediately after fitting is usually caused by incomplete locking, dirt on the sealing face, or the cartridge not sitting straight. Remove the cartridge, wipe the filter head with a clean damp cloth, inspect the cartridge end, and refit it squarely. Do not add tape, grease, glue, or sealant. The seal is made inside the housing, not on an external thread.

If no water comes from the dispenser after the change, wait 30 seconds and try again. Air in the line can make the first flow uneven. If there is still no flow, remove and refit the cartridge, then check that the fridge water supply has not been shut off during the job. Some fridges make a louder pump or valve noise while air is being expelled. This should reduce after several litres have passed through.

If the cartridge will not turn, do not use pliers on the cartridge body. Extra leverage can damage the internal housing, which is more expensive than the filter. Improve grip with a dry cloth, press the cartridge inward gently, then turn. If it still will not move, empty the nearby shelf area and work with both hands at the same height as the housing.

If water tastes of carbon after fitting, continue flushing in 1 litre batches. Fine black specks at first use are usually carbon fines from the filter media. They should clear during flushing. If the taste is metallic, chemical, or does not improve after several litres, check the appliance manual and the water supply, not only the cartridge.

Special cases before ordering or forcing the cartridge

Some Bosch fridge freezers in UK homes have had parts replaced, doors changed, or external plumbing altered by a previous owner. Treat the physical housing in the appliance as more important than the badge on the door. If you cannot see an internal cartridge head, do not assume a cartridge is hidden behind trim. Check the appliance cavity, the lower rear area, and the water pipe route for an external inline filter instead.

On fridges that have stood unused for more than 2 weeks, flush more water than usual after fitting. A practical amount is 5 litres before drinking, then another 1 or 2 litres if taste is still flat. If the appliance has been disconnected, check for leaks at the rear water connection as well as at the internal filter housing.

For rented homes, note the fitting date on paper or in a phone reminder. A 6 month interval is easy to miss when several people use the fridge. If the dispenser flow becomes much slower before that time, check the supply tap and pipe first, because low household water pressure can look like a blocked filter. For general troubleshooting questions, see the fridge water filter FAQ.