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  4. WaterShield ( Water Shield ) - Which filters and membrane ( Reverse Osmosis )

3 Stage RO Unit
Classic WaterSheild 3 Stage RO Unit.

Recommendation is to change the 2 filters that are vertical every 6 - 12 months.
And we would recommend using ( 2 ) of the CTO 2 Carbon Block for both.
CTO carbon block.

And the recommended TFC membrane most people would use is the 50 GPD

But note it is not always necessary to change the horizonally mounted membrane,
as the "membrane", can last 2 - 5 years in most applications.

Various membrane sizes ( GPD ) rates are available.
The physical dimensions are standard and the same for all models.
Older models used the 36 GPD meter, but as that is no longer made,
you will need to use the new 50 GPD membrane.
36 gpd
50 gpd


And "newest" "WaterShield 50" ( Water Shield 50 ) uses S1764RS membrane
Similar to the Microline brand made by Clack Corporation,
or you can also use the 50 GPD membrane S1229RS ( NSF approved version ).
It uses special filters,
S7028 as pre-filter
S7025 as post filter.

The S1764RS, S7028, and S7025 can be purchased as a SET = WS50RO-Set

Service Manuals for the the newer Style 
the Classic and the Big Pump reverse osmosis can be viewed / downloaded,

Membrane Rinsing Directions

It says: Element must be rinsed under pressure before being soaked or stored in water.
The reason being they are shipped with a "preservative" ( = Sodium Metasulfite ), which if not fully rinsed,
may have a "laxative" effect if consumed.
Discard product water 2 hours minimum
( some directions that come with new units have increased this to 8 hours,
or multiple draining the holding tank before using the water )

before using for drinking water or food-related products.

What does this mean in layman’s terms?

Either DRAIN your storage tank, and then let it FILL UP and then DRAIN again...
and then it is okay to use the RO water after the 2nd time it fills up,
just leave the RO Faucet OPEN for 2 hours.... the flow will be very slow, but that is normal.
After 2 hours, shut off Faucet and let the storage tank fill up ( over night or several hours at least ).
Then it will be okay to use.

Sediment Pre-filter ( first filter your water enters ) can be Sediment Only = Sediment 5 micron

Second Pre-filter is also the Post Filter when only 3 "stages" are used ( diagram is showing 4 "stages" )
and it can be GAC orCTO carbon block.
And the CTO Carbon Block is recommended for this "stage", as the 2nd filter under most units.
This should always be a Carbon Filter and in most cases the Pre-filter ( 1st filter ) should also be a Carbon Filter
( REQUIRED to be a Carbon filter, if your water source is chlorinated ).
see: CTO 5 Micron Carbon Block

The INLINE Filter ( final stage or Post Carbon Filter in diagram below ) used on some, not all units
and is typically the 10" and has 1/4" threaded openings. see: Sealed Carbon 5 micron In Line

If yours does NOT have this "stage", then do not order one.
NOTE: Some new models use special In Line filters with built in "quick connect" for use with 1/4" or 3/8" tubing,
and cost more because the fittings are build in.
Also, the average RO system only has 3 stages ( pre-filter, membrane, and post filter ),
and the "Inline" post filter is not used ( nor required ).

How do we know when it's time to change the filters?>

* You don't know unless you waited too long.....
Prefilter clogs, and water production drops.
And if in chlorinated water source, the membrane can be damaged, if prefilter not changed soon enough.

Typical RO and Filters Housings,
4 Stage,


To SEE How To Install a typical Reverse Osmosis System

YouTube video = https://youtu.be/wGQzOR4Mso8

For basic filter change explained

We recommend this these videos on YouTube, https://youtu.be/y7a9QPSDqdI


Or this longer more detailed video, https://www.youtube.com/watch?v=c3Ly2Zh3j2Q

For basic membrane change explained

We recommend this fine video on YouTube, https://youtu.be/EvtMM9s2Fuk?t=93

Comprehensive Changing and Sanitizing of the RO System explained

We recommend this fine video on YouTube, https://www.youtube.com/watch?v=-kF_80OsU-I

*** Cleaner used in the above Video =Sani-System Liquid Sanitizer for RO

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