If your Fleck 5600 ( or similar Hankscraft design) Valve is not drawing ( sucking in ) the salt water from your brine tank,
then here is a list of things to check and information about Brine Suction Failure.
Brine Tank Overflow
and watch videos about these parts,
Refilling when it should Sucking Water out
Water Flowing to Salt Tank ( o-ring 13302 issue )
Check Injector Set
Check Drain Line Flow Control ( DLFC )
Replacing Pistons and Seals
And if the problem is the Brine Pick Up Float Shut off see this replacement,
Brine Pick Up with Float Shut
Check all connections from the Valve to the Brine Pick Up Tube.
Do you have the required "ferrule" on the brine tubing, as that is what creates the "seal" and not the threads of the fittings.
Check to see if the Valve is creating the required Suction.
Remove the Brine fitting at the Valve ( brass nut ) and manually advance to the Brine Rinse cycle
- Be sure you are fully "IN" the Brine Rinse cycle - You need to turn the knob about a 1/4" PAST the words "Brine Rinse" to be sure the Brine Valve is being pressed open / down by the brine cam gear.
Check that your Brine Cam Gear ( video = https://youtu.be/kfFG3YllXaQ ) has not broken off inside the power head.
At this point -
You should have suction that you can hear and feel at the brass connection of the Valve.
If you do not,
there is a problem with the Valve ( injector, main seals, or a drain flow restriction ).
If you do have suction,
then the problem is Not with the Valve, but has something to do with either the Brine tubing, connections, or the Brine Pick Up tube in the salt tank.
As it's possible for the Brine Pick Up to be blocking flow out due to pre-mature "air check".. rare, but something to consider if Valve is working and connections are all good ).
And last but not least, on an older systems that has been using Pellet type salt for many many years, you can have a blockage at the bottom of your Brine tank created by old un-dissolved salt.
** In Summary, regarding the problems we see most often,
If the problem is FILLING when there should be SUCTION,
There are really only 3 common causes for the problem.
In order of most common to least common,
1 ) Drain obstruction ( partial clog or back pressure in drain pipe, especially common in drains that run "uphill" )
2 ) Injectors ( screen clogged, or injector nozzle / throat cracked, or not screwed in securely to the injector drain module )
3 ) Seals and Main Piston ( badly worn, damaged, or in the wrong order, or you put the mechanical Piston in an Electronically controlled Model ).
* In Summary:
There are only a few things in the valve that would effect the suction cycle.
The "condition" of the Seals and the Piston is one factor.
In order for the suction to work, the "pressure" that is on / in the TANK have been released ( out to drain ).
Otherwise the "weak" brine flow from the injectors can not enter the resin tank.
The "seals" must divert the flow / pressure away from the resin tank.
All the water must pass through the Injector, which creates the suction to draw in the brine water.
This then slowly enters the tank from the top, and works down through the resin beads, and then out the drain hose.
And problems any of the things listed above -
with the "SEALS", "Piston" ( coating or position ), Injector, Injector Screen, DLFC button,
or "restrictions" in the drain hose ( creating "back pressure" ) can cause the Suction Cycle to fail.
* One very RARE cause ( if all others have been ruled out ),
is the CONDITION of the MAIN GEAR where is "pulls" the Main Piston UP.
If there is a deep GROOVE worn into the Main Gear,
it's possible the Piston is not being moved to the correct position
( resulting in "leaking" internally past a "seal" that should blocking / re-directing internal flow through the valve ).