A. O. Smith Drinking Water Filter
Max 4 Water Filter*
0.0001 micron Reverse Osmosis water purifier, with refill cartridges designed to be easily replaced on your own.
*may be paired with an AOS hot water tap


Fully integrated system
The Max 4 water purifier is located under the sink with no additional pumps, tanks or exposed parts.
Its innovative side loading design is convenient and does not require users to remove an entire system to replace filters.
Get fresh water in seconds
With the latest RO water filter technology, Max 4 produces a jet of instant, clean water at 1800ml/min. Conventional RO filters operate at 200ml/min.
Tankless and space saving
Producing clean water 9 times faster eliminates the need for a tank. While conventional RO filters are bulky, the Max 4 is a tankless, sleek design that takes up less space in your kitchen.
Patented DIY Technology
Patent ZL 200910201739.8
Change your filters in two easy steps:
Step 1:
Lift handle and pull filter out
Step 2:
Push new filter in.
Each filter is fitted with a mircochip that records your volume consumption and life of the individual filter. Change only the filters which are depleted.
Tankless and space saving
Producing clean water 9 times faster eliminates the need for a tank. While conventional RO filters are bulky, the Max 4 is a tankless, sleek design that takes up less space in your kitchen.

Stage 1: Heavy duty sediment pre filter
In the first stage, a heavy duty pre filter clears out impurities and sediments from the water. This prolongs the life of the stage 2 and 3 filters. Sediment filters operate efficiently for up to a year.
Stage 2: Patented carbon chlorine filter
Patent ZL201520326026.5
Patented carbon filter intercepts and removes an extremely high rate of 99.9% of bacteria and chlorides. Odours are eliminated and water taste improves significantly.
Stage 3: Patented high precision RO filter
Patent ZL 200910201739.8
Traditional RO filters have water entering at one end and leaving at the other. These high pressure RO systems usually last no more than a year.
The Max 4 high precision filters can last up to 4 years. They are designed to allow water to stream in from both ends of the filter and be purified through the length of the membrane. This design not only preserves the integrity of the filter for longer, it also improves the entire filtration process.
AOS RO Technology: Highest water retention rate
To obtain the cleanest water, all RO water purifiers can retain only a percentage of the water. The more advanced the RO filter, the higher the retention rate.
While other RO water purifiers have a water retention rate of 25%, the AOS RO filter holds the patent for the highest water retention rate of 75%.
Dual filter replacement indicator
Light indicator at both hot water faucet and water purifier changes colour to reflect life of the filter, giving you ample time to arrange for filter replacements.
White – Normal
Orange – 5% life
Red – 0% life
Automated self-cleaning
Max 4 auto-cleanser performs a flush through the entire system. It is activated:
- upon powering up or after a reset
- for every 30 min of continuous usage
- for every 72 hours of inactivity
AR75
AOS Water Filters
High Precision RO drinking water purifier. Tank size suitable for families of 4.
Reverse Osmosis water filters
AOS water purifiers use Reverse Osmosis (RO), the top international standard for clean drinking water
RO filters use high precision filtering up to 0.0001 microns.
Most water purifiers in Singapore filter up to 0.001 microns.
PUB uses Reverse Osmosis (RO)
PUB uses RO and ultraviolet (UV) to purify our water.
These are proven, top in range methods for purification.
RO Water – #1 in USA and China
In places where water purification is essential, RO is always used as 0.0001µ filtration ensures that all trace heavy metals are removed.
RO is the top water purification system used in USA and China.
Filter replacement indicator
Light indicator at drinking water tap changes colour to reflect life of the individual filters, giving you ample time to arrange for filter replacements.
White/Green– Normal
Orange– 5% life
Red– 0% life
Quick notes on filter change
Filter Change
- After changing filter 1, 2 or 3, let water run from the filter tap for 15 min.
Caution
- Do not let filter tap run over 20 min or this will cause ‘leak protection’ to be activated and system will shut down.
How to use the MAX4?
Product Specifications
under-sink installation
