Bosch and Siemens UltraClarity water filter

If your fridge is one of the models below, the water filter you need is the 644845 (UltraClarity).

Bosch B22, B26, B30 and B36 American style ranges, and the equivalent Siemens KA62 series built on the same BSH platform.

Specification

Manufacturer part number	644845 (UltraClarity)
Equivalent codes	REPLFLTR10, BORPLFTR10, 9000077104, 9000194412
Fitting position	Internal cartridge, UltraClarity housing system
Capacity	Not published precisely by the manufacturer for this pack; check the litre or gallon rating printed on the box you buy
Recommended change interval	Every 6 months
NSF certification	Sold with NSF certification by most retailers; check the specific standard printed on the box, since it is not confirmed on an official Bosch or Siemens page

What does not fit

Not applicable: this is a single shared platform across Bosch and Siemens.

How to replace it

Locate the filter compartment described above and turn off the fridge's water supply if your model has a shut off valve.
Turn the old cartridge a quarter turn in the direction marked on the housing, or press the release catch, then pull it straight out.
Check the reference printed on the old cartridge against 644845 (UltraClarity) before fitting the replacement, since two cartridges from the same brand can look alike but not seal the same way.
Remove the protective cap from the new cartridge, then push it into the housing and turn it a quarter turn until it locks.
Run 2 to 3 litres of water through the dispenser before drinking it, since new cartridges release carbon dust on their first use.
Reset the fridge's filter indicator, usually a button held for a few seconds, so it counts down correctly to the next change.

Common mistakes

Buying by fridge brand alone instead of checking the exact part number, which on a brand with more than one system leads to a cartridge that does not fit.
Leaving the filter well past its change interval, which reduces flow rate and can let the carbon block become a place for bacteria to grow rather than filter them out.
Forcing a cartridge that does not turn or push in without resistance; if it does not seat cleanly, it is very likely the wrong reference.

How this reference sits in the Bosch range

644845 (UltraClarity) is the only reference published for Bosch on this site, because it is the only one confirmed against a manufacturer or distributor source. If your fridge does not match the fitment described above, see our guide for an unlisted model rather than guessing.

Where this information comes from

The specification above is taken from UK retailer uk-fridge-filters.co.uk product listing, cross checked against US fitment lists on discountfilterstore.com and redstagsupplies.com confirming the shared Bosch/Siemens reference. References are re-checked when a manufacturer renumbers a pack; if you find a discrepancy with your own fridge, tell us and the page is corrected.

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Preparation, tools and working space

Allow 10 to 15 minutes for the change, plus another 3 to 5 minutes for flushing at a normal dispenser flow. You do not need a filter wrench. If the cartridge does not move by hand, stop and check the lock position, because extra leverage can crack the plastic head.

Use one dry towel under the filter area and one cup or tray holding at least 500 ml, because a small amount of water normally drains from the housing.
Keep a torch or phone light ready, since the part number and arrow marks are often moulded or printed in low contrast plastic.
Leave at least 150 mm of clear space in front of the filter compartment so the cartridge can be pulled straight out without bending the head.
Wash your hands before handling the new cartridge seal. Grease or grit on the seal can cause a slow drip after fitting.
If the fridge has been moved recently, wait 30 minutes before testing the dispenser, so the appliance is stable and the water tube is not under strain.

Take a clear photo of the old cartridge before removal, including its label and its locked position. This gives you a reference if the new cartridge does not seat in the same orientation. For other Bosch fridge filter references and model notes, use the Bosch filter guide rather than matching by appearance only.

Detailed fitting sequence and checks

Open the filter cover fully and look at the direction marks before touching the cartridge. If there is a drip tray below the dispenser, empty it first, because the flushing stage can fill it quickly.

Release water pressure by pressing the dispenser lever for 5 to 10 seconds after the water supply is off, if your installation has a shut off valve. This reduces the sharp spray that can happen when the cartridge seal breaks contact. Hold the old cartridge level as it comes out, because 50 to 150 ml of water can remain inside it.

Before fitting the new cartridge, inspect the filter head inside the fridge. The two common problems are a loose rubber seal left behind by the old cartridge and a small chip of plastic near the locking slots. Remove loose debris with a clean finger or cloth only. Do not use a screwdriver inside the head, because the sealing face is easily marked.

Push the new cartridge in squarely, using steady pressure from the centre of the end cap. A correctly aligned cartridge should move the last few millimetres without a crunching feel. After locking it, dry the area completely, then dispense water for 20 seconds and inspect with a torch. A slow leak often shows as a shine around the joint rather than as a visible drip.

Check point	Typical figure to use	What it tells you
Time to remove and fit	10 to 15 minutes	Longer usually means the cartridge is not aligned or the compartment is obstructed.
Water caught during removal	50 to 150 ml	More than this suggests pressure was not released or the cartridge was tilted.
Initial flush volume	2 to 3 litres	This clears loose carbon fines and trapped air before drinking.
Leak inspection period	2 minutes after flushing, then again after 30 minutes	Some leaks appear only after the housing is under pressure for a while.

Frequent faults and how to recover

If the cartridge turns only a few degrees and stops, do not force it past the stop. Pull it back out, compare the key shapes with the old cartridge, and check that the old seal is not sitting in the filter head. A doubled seal can make the cartridge feel close to fitting while preventing it from locking.

If the dispenser spits air after the change, keep dispensing in 10 to 15 second bursts with short pauses between them. Air in the line is common after opening the filter circuit. If flow does not settle after 3 litres, check that the water supply valve is fully open and that the cartridge is locked in its final position.

If water tastes dusty after flushing, discard another 1 litre and clean the dispenser nozzle. Fine carbon can collect at the nozzle and re-enter the first glasses even after the cartridge has been cleared. If the taste is chemical, plastic, or sour after several litres, stop using the water and recheck the cartridge source and packaging.

If the filter warning light does not reset, press the reset control for a measured 5 to 10 seconds, then close and reopen the door. Some control panels ignore a quick press. If the panel is locked, unlock it first, then reset. For general reset and troubleshooting questions, see the fridge water filter FAQ.

Special cases before you order or refit

If the appliance has been unused for more than 2 weeks, fit the filter as normal but flush at the upper end of the range and discard the first full ice bin if the fridge has an ice maker. Standing water in the internal line can carry stale taste even when the cartridge is new.

If the fridge is installed in a tight cabinet, measure the swing of the filter cover before ordering spares for a rental or service visit. A door or side wall only 20 to 30 mm too close can stop the cartridge being removed straight, even though it looks accessible.

If the old cartridge has no readable label, do not rely on colour, cap shape, or the fridge badge alone. Remove it, photograph the head and cartridge end, then compare the printed reference on any paperwork or previous invoice. A cartridge that seals incorrectly can leak inside the fridge lining, where damage may not be visible until later.