Sodium Hypochlorite Vapor Lock in Metering Pumps
NaOCl off-gasses in suction lines — the real fix starts with the system design, not with swapping pump technology.
Sodium hypochlorite can release gas during storage and dosing. Gas accumulation in the suction piping or dosing head can reduce volumetric efficiency, interfere with check-valve operation, and in severe cases cause loss of prime or interruption of chemical feed. The real fix starts at the system level — minimizing where gas can generate and accumulate — before a specific pump technology gets selected.
Gas in the Suction Path, Not a Weak Pump
Sodium hypochlorite is an outgassing chemical — it's real, documented behavior that metering-pump manufacturers explicitly design around. When gas bubbles form in static or low-flow suction piping (especially at higher ambient temperatures, or with aging chemical), they can occupy volume in the pump head or dosing chamber that should be occupied by liquid, cutting the effective pumped volume. In severe cases, enough accumulated gas prevents the pump from re-establishing prime at all. The mistake isn't picking the "wrong" pump brand — it's designing a suction path that gives gas somewhere to accumulate in the first place.
Two Steps, in Order
Minimize gas generation/accumulation first
Short suction piping, minimum practical suction lift, flooded suction where appropriate, no unnecessary high points that trap gas, correctly sized suction tubing, minimal dead volume, correct pump-head orientation, fresh chemical where practical, storage away from heat/light, proper tank venting.
Then select a pump suited to the duty
A diaphragm metering pump specifically designed to deal with outgassing fluid, a pump head with automatic degassing, or a peristaltic pump when its operating characteristics fit the application — not one technology assumed superior for every case.
Frequently Asked Questions
Why does sodium hypochlorite cause metering pumps to lose prime?
Sodium hypochlorite can release gas during storage and dosing. If that gas accumulates in the suction piping or dosing head, it reduces volumetric efficiency, can interfere with check-valve operation, and in severe cases causes loss of prime or interruption of chemical feed.
Is a peristaltic pump always the right fix for sodium hypochlorite vapor lock?
No. The real fix starts at the system level — minimizing where gas can generate and accumulate in the suction path — before a pump technology gets selected. Depending on the application, a diaphragm metering pump designed for outgassing fluids, an auto-degassing pump head, or a peristaltic pump can all be the right answer. Peristaltic is a real option when its operating characteristics fit the duty, not a universal default.
What suction-line design reduces sodium hypochlorite off-gassing problems?
Short suction piping, minimum practical suction lift, flooded suction where the layout allows it, no unnecessary high points where gas can trap, correctly sized tubing, and minimal dead volume in the line. Chemical age, storage conditions (away from heat and light), and proper tank venting also affect how much gas is generated before it ever reaches the pump.
Losing prime on a sodium hypochlorite feed system?
Send LibertyCES your suction-line layout, chemical strength, temperature, and current pump — we'll help identify whether it's a system design issue or a pump-technology mismatch.
Ready to buy or need a fast answer? Call, text, or email James directly — (559) 395-5500 · james@libertyces.com.
Free download: the five-step suction-path check, the storage and feed decisions behind it, and a full source ledger. Get the Hypochlorite Suction-Path Blueprint →