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  5. Air Injection Oxidizing Filter System = AIO
An AIO Filter ( AIR INJECTION OXIDIZING FILTER SYSTEM ), when properly applied, is an efficient and cost effective system for the removal of iron and sulphur. An AIO system maintains a compressed “air pocket” in the top of the tank while the system is in service. As the water passes thru the air pocket, iron and sulphur are oxidized. Additionally, dissolved oxygen is added to the water. An AIO filter media bed then removes the iron and sulphur that has been oxidized from the water ( traps in the media bed ).

A daily backwash will remove accumulated iron and replenish the filter media bed. 
The regeneration process also adds a fresh air pocket to the system.
Application Parameters pH (Minimum of 6.8 ) and Iron (Maximum typically 7 ppm ) and Sulphur (Maximum typically no more than 8 ppm ).
Note: Three different medias are used depending on whether the problem with the water is primarily IRON or Hydrogen Sulfide odor.

*** We do NOT sell this system -- We can get most parts, if you have part numbers or can provide descriptions with photos of what have and what you think you need.

** Here is a link to Service / Installation Manual for a popular Brand of AIO ( sold through Nelsen Corporation ),


The Media can be BIRM ( iron removal ), Catalytic Carbon ( odor removal ) or Katalox Light ( a combination of Iron and Odor removal possible ).
It all depends on the application ( what is needing to be REMOVED from the Water - Iron or Hydrogen Sulfide and the LEVELS of these in the source water ).

TESTING your AIR POCKET ( key to system working properly ).

Your AIO system WILL have some Air going out the Drain at the beginning of the Brine Rinse ( suction ) cycle.
The way to TEST if your system is creating and holding an Air Pocket is to manually start the Regeneration,
and observe if AIR comes out at the beginning of the first cycle ( Backwash 15 minutes ).
You should get some AIR at the beginning of every Backwash. 
If you don't, then the system is not working properly, 
and you need to clean or replace the Main Piston and the Seals & Spacers ( or Spacer Stack for Clack type valves ).

The two critical ( and unique ) parts used to this Valve are:
1 ) Check Valve on the Inlet to prevent the "air" from escaping.
Here is photo of this used with a Fleck valve, but can also external on the water piping coming into the valve.

2 ) A screen ( and check valve ) used on the Brine Connection to "draw" the AIR into the tank ( during the "suction" cycle ).
There are many different "Styles" used. The only "purpose" of this brine check valve is to prevent a little water from squirking out as the valve returns to IN SERVICE portion,
as the valve ends the Regeneration process. It is not "holding" the air in the tank. Your internal SEALS ( and piston ) are what holds the air in the tank.

*** NOTE: We stock / list a few common types of these parts, see Below.

And for "iron removal" issues, see more information -
"Do I need an Iron Filter?"

If you need a complete NEW AIO system, then we would recommend ( but do not sell ),

The NWTS Signature Series AIO™ features a unique patented process. Most systems purge the air pocket in the tank violently during the regeneration process potentially damaging plumbing and creating an excessive amount of noise. Our patented-process slowly releases the air pocket during regeneration before replenishing the tank with a fresh pocket of air. Additionally, our system will delay the regeneration process and air release if water is being used in the home or business. Once water flow stops, the regeneration process begins slowly releasing the air from the system. On some competitive systems, water use will prevent the release of air due to the internal design limitations of the control valve or violently release the air once water flow stops. Professional Water Treatment Dealers can now offer the important advantages of the Nelsen Water Treatment Solutions AIO with Control Flow Technology to their customers.
If the Valve being used is Clack WS1,
then this information might be helpful to troubleshooting your AIO problems.

The check valve on the "brine" port with screen is not "critical".
It's just there to keep water from squirting out of the valve.
Most of the time this line is only going to be used for Suction.
And unless it's clogged, it does not affect the air pocket in the tank.
You can remove the screen and check the opening with your finger for suction.
Inline Check Valve 3/8"

There are three things that normally fail.

1 ) Spacer Stack Assembly leaking to drain.
Remove the Drain elbow ( when unit is not "running" a cycle ),and observe if any water seems to be coming from the valve body.
Clack Drain Elbow Port
If you see the water "rising" from this port ( observe for 2 - 3 minutes ),then you have an internal leak, and you need to replace the Spacer Stack and just be safe, the Piston too,
see Spacer Stack Assembly for WS1 valves,
and Piston used with WS1 valves,

2 ) Check valve on the Inlet port ( Water Line ).
Which could "INSIDE" the valve body ( remove ByPass from the Valve Body and look in the port hole ),
WS1 Inlet Port Identified
could be "External", which is usually a Check Valve on the Water Line just before it connects to your valve.

3 ) Be sure to check / clean your INJECTORS as you want good suction to pull in the AIR needed for the oxidization process.

One other NOTE: 
The system should be set to RUN every night to ensure a good air pocket 
and frequent backwashing of the oxidized sediments created in the process.

And if you made it this far into the Article,
you might get some useful information from this poor audio presentation that Pentair Water posted April 2, 2021 on Youtube,

AIO Media Applications

If you have a lot of IRON in the water, 
The manufacture recommends that you replaced these KEY parts annually.
V3005 rust Clack injector ports iron - rust
Clack WS1 type valves,

Fleck 2510 AIO parts:

Fleck 5600 AIO parts:

Video about "cleaning",

Video about the 3 versions - using either BIRM ( FOB ), CARBON ( FOC ) or Katalox ( FOK ) as media,

Products [20]

Discontinued - use 60090 and 60121
0 Items
odor, hydrogen sulfide, rotten egg, smell,AIR INJECTION, OXIDIZING FILTER,AIO,iron