Stone Circuit
Installing the stone hose, isolation valve, inline check valve, and carbonation stone — and why the push fittings matter.
Stone circuit
The stone circuit is where CO₂ enters the beer. Gas leaves the FizzWizz through the stone hose, passes a series of one-way valves, and diffuses into the tank through the carbonation stone.
This is the circuit most exposed to product, so the valves that protect it — and the fittings that seal it — matter as much as the stone itself.
The circuit path
| Order | Component | Purpose |
|---|---|---|
| 1 | CO₂-in solenoid (inside the unit) | Opens gas flow to the stone |
| 2 | Flow controller (inside the unit) | Meters the flow rate. The ball indicates rate |
| 3 | Stone hose | 5/16 inch ID NSF tubing from the unit to the stone assembly |
| 4 | Inline check valve | One-way valve in the hose — blocks liquid travelling back toward the unit |
| 5 | Stone Isolation Valve | Manual valve that isolates the stone. Used in Check 7 |
| 6 | Sanitary Check Valve | Second one-way valve, immediately before the stone on the wetted side |
| 7 | Carbonation stone | Porous ceramic diffusion element inside the tank |
See the Pneumatics Schematic for the diagram and the full component glossary.
Connecting the stone hose
Power the FizzWizz OFF before connecting or disconnecting any hoses.
Power off
Switch the FizzWizz OFF.
Connect the hose to the unit
Fit the stone hose to the STONE connection on the FizzWizz.
Fit the inline check valve
Install the inline check valve in the stone hose, oriented to block flow back toward the unit. Check the flow direction arrow if one is marked.
Route the hose to the stone assembly
Route the hose to the tank, avoiding tight bends and anywhere it can be stood on or crushed.
Assemble the stone end
Fit the isolation valve, check valve, elbow, and carbonation stone in the correct order. The Check Valve page has the assembly order, including the vertical mounting requirement.
Fit the stone into the tank
Install the carbonation stone in the tank port. See WizzStone-Combo for assembly of the carrier and stone.
Push-to-connect fittings
The stone circuit uses push-to-connect fittings, including a ¼ in NPT pneumatic push fitting where the hose joins the stone assembly.
Push-to-connect fittings are a common source of small leaks. Check these first when the flow meter ball behaves oddly, when the stone circuit will not hold pressure, or when a tank will not build pressure. A small leak here is easy to miss and produces symptoms that look like a component failure.
To test a suspect fitting, spray it with soapy water and look for bubbles. This is the first step for Health Check Ident X and part of the diagnosis for Ident V.
The isolation valve
The stone isolation valve is a manual valve that isolates the carbonation stone from the rest of the circuit. It is used to prove the stone circuit holds pressure in Check 7.
| Valve position | What it does |
|---|---|
| Open | Normal operation — gas flows to the stone |
| Closed | Isolates the stone. Used to test whether the circuit holds |
During Check 7, the flow meter ball should be adjustable with the valve open, and should drop when the valve is closed. If it does not drop, there is a leak between the FizzWizz and the isolation valve — check the hose and push fittings.
Carbonation stones
The stone is a porous ceramic element. The WizzStone-Combo uses a 16 in stone with 0.5 micron pores, producing very fine bubbles and high CO₂ transfer.
Because the pores are small, the stone clogs easily and must be cleaned after every use. A dirty stone becomes hydrophobic — it repels water rather than diffusing gas — and is a leading cause of low carbonation.
See WizzStone-Combo cleaning for the torpedo and ultrasonic methods.
Setting the flow rate
The flow controller on the side of the unit sets how fast CO₂ enters the stone. The correct rate depends on stone length, porosity, product height over the stone, and finish gravity.
Use the BrewWizz app's CO₂ Stone flow rate calculator — see Setting the CO₂ flow rate. The WizzStone-Combo supports up to 16 CFH.
Checking the circuit
After connecting, run Check 7 — Stone/Isolation Valve to confirm the circuit holds. If carbonation is low and the Health Check passes, see Carbonation & Brite Pressure.
Next step
Arm Circuit & Separator
Connect the arm hose and the separator — the unit's main protection.