How to Change an Under-Sink Water Filter
To change an under-sink water filter, shut off your cold water supply valve under the sink. Relieve the water line pressure, take out the used cartridge, seat the new cartridge firmly, and turn the water back on slowly to check for leaks.
Run water through the line to flush the new cartridge before drinking from it. Having a small bucket or a towel ready helps catch any small drips during the swap.
Understanding your under-sink system
Under-sink filter systems mount neatly inside your base cabinet to supply cleaner water straight to your tap. An under-sink filter that is not RO connects to the cold water line only, with no drain line. A reverse osmosis system has a membrane and a small drain line.
A direct-connect under-sink system usually attaches directly to your existing cold water supply line or feeds a dedicated drinking faucet. These systems use replaceable cartridges that twist or snap into a mounted filter head. The Waterdrop 10UA Direct-Connect Under-Sink Filter, part number WD-10UA, is an example of a direct-connect system. Another style is the Waterdrop TSB-ALK 3-Stage Under-Sink System with Dedicated Faucet, part number WD-TSB-ALK, which uses multiple stages.
Cartridges contain filter media designed to treat water as it flows through the unit. Knowing whether your setup is a direct-connect unit or a multi-stage system helps you handle the hardware properly.
When to change your under-sink cartridge
Typical change intervals are rough guidance. Under-sink cartridges are typically changed every 6 to 12 months. The interval on the product page and in the manual always wins.
A filter is built to handle a set amount of water, its rated capacity. Change it sooner if water flow slows or the filter light comes on.
For the Waterdrop 10UA direct-connect model, the stated filter life varies by the cartridge rating, such as 12 months/8,000 gallons, 24 months/16,000 gallons, or 36 months/24,000 gallons, with an option listed as 11000 Gallons. If water pressure drops noticeably at your faucet before that time arrives, the cartridge has likely reached its working limit and needs an early replacement.
Step 1: Turn off the water supply
Always begin any filter maintenance by shutting off the incoming water line. Working with an active water line can cause sudden spills inside your cabinet.
Locate the cold water angle stop valve on the wall or pipe beneath the sink. Turn the handle clockwise until it stops moving to fully shut off the water flow.
Once the valve is closed, open the faucet connected to the filter. Let any trapped water drain out completely. This relieves pressure inside the line and makes it much easier to detach the cartridge without fighting internal water pressure.
- Find the cold water shutoff valve under your sink.
- Turn the valve completely clockwise to close the water supply.
- Open the sink faucet to release pressure and drain standing water.
Step 2: Remove the old cartridge
Place a small towel or pan directly under the filter body. Even after you relieve line pressure, a small amount of residual water will remain inside the cartridge and bracket.
Grasp the cartridge body firmly with your hand. For a typical direct-connect unit, rotate the cartridge a quarter turn counterclockwise to unlock it from the manifold head.
Pull the cartridge straight down to separate it from the bracket. Keep the cartridge upright as you pull it away so that leftover water inside does not spill across your cabinet floor. Set the used cartridge aside.
- Place a towel or shallow bowl directly below the filter head.
- Turn the used cartridge a quarter turn counterclockwise to release the lock.
- Lower the cartridge straight down and keep it upright to avoid spills.
Step 3: Install the new cartridge
Unpack your replacement filter and remove any protective plastic covers or shipping caps from the top connection ports. Inspect the top fitting to verify the seals are clean and seated properly.
Align the top of the new cartridge with the receiver ports in the mounting head beneath your sink. Push the cartridge upward into the head until it seats fully into position.
Turn the cartridge a quarter turn clockwise until it stops and locks in place. The cartridge should feel secure and properly aligned with the bracket markings before you introduce water.
- Remove protective packaging and transport caps from the top of the new cartridge.
- Line up the cartridge top with the mounting head ports.
- Push upward and turn the cartridge a quarter turn clockwise until firmly locked.
Step 4: Check for leaks and flush the cartridge
Slowly turn the cold water supply valve counterclockwise to restore water flow to the system. Opening the valve slowly prevents sudden pressure spikes across the fittings.
Inspect the connection point where the cartridge locks into the head. Check all visible tubing connections for any drops of water. If you notice any weeping, turn the water supply off, reseat the cartridge, and turn the valve back on.
Run some water through a new filter before you drink it. Follow the flush steps on the box or the product page. Let the water run continuously to purge trapped air pockets and settle the new filter media before daily drinking use.
- Turn the cold water shutoff valve counterclockwise slowly to restore water.
- Watch the connection head closely for any drips or moisture.
- Open the faucet and run water according to the flush directions on the box.
Find the right replacement filter by model
To ensure a proper connection, you must match the replacement cartridge directly to your system. Fit is matched by model: search the model of your system, the number on your old filter, or your fridge model.
Many models list their model number on a label: on the side or front of a water system, on the old filter, or inside a fridge on a side wall. For example, the Waterdrop 10UA system lists its replacement filter as WD-RF10/15/17. Checking that label prevents mistakes and ensures the cartridge fits the head securely.
Every filter and system H2O Buddy sells is made by Waterdrop. Fridge filters are compatible replacements, not parts made by the fridge brand. If you ever need assistance remembering maintenance schedules, H2O Buddy can email a free reminder when a filter is due, and subscribe and save never charges automatically.
- Locate the model label on the front or side of your filter system housing.
- Read the part number printed on your existing cartridge.
- Search your specific system model number to find compatible replacement cartridges.
When to call a pro
If you are not sure about plumbing work, hire a licensed plumber. Stop and call a licensed professional if your shutoff valve will not close completely, if fittings leak after reseating, or if your pipes show corrosion.
Filters for this
Check your model before you order. Search it above, or send us a photo of the label.
Questions
How often should an under-sink water filter cartridge be changed?
Typical change intervals are rough guidance, and under-sink cartridges are usually changed every 6 to 12 months. The interval on the product page and in the manual always wins. A filter is built to handle a set amount of water, its rated capacity, so change it sooner if water flow slows or the filter light comes on.
Do I need to turn off the main water valve to change an under-sink filter?
No, you usually only need to turn off the cold water supply valve located directly under the sink. Turn off the water supply before changing an under-sink, inline or whole house filter. Relieve pressure by opening the faucet before removing the cartridge.
Why do I need to flush a new filter before using the water?
Run some water through a new filter before you drink it. Follow the flush steps on the box or the product page. Flushing clears out trapped air pockets and prepares the filter material for regular daily use.
How can I tell if my system is reverse osmosis or direct connect?
An under-sink filter that is not RO connects to the cold water line only, with no drain line. A reverse osmosis system has a membrane and a small drain line. Direct-connect units hook into your cold supply line to feed either your main cold tap or a dedicated drinking faucet.
Keep reading
General information, not a substitute for your system or fridge manual. Our filters and systems are made by Waterdrop. Brand names are used only to show fit.