The symptom pattern

George is doing a normal wet pickup — a spill, a flooded carpet, a wet workshop floor — and then, without warning, stops drawing anything up. The machine is still running and still loud, but nothing more comes through the hose no matter how much water is sitting there to collect. Because the motor’s still audibly working, it reads as a blockage rather than something the machine is doing on purpose.

What’s actually happening

Numatic’s own fault-finding table for this exact symptom — “vacuum will not pick up liquid” — gives the float valve as the named cause, identified by a change in the motor’s pitch as the giveaway. George’s recovery tank has a float-operated water level limiting device fitted specifically to stop water reaching the motor once the tank is full; when it closes off suction, the motor note audibly changes because it’s now pulling against a sealed path rather than through open airflow. It’s a safety feature doing its job, not a failure, and the manual is explicit elsewhere that a dirty or damaged float can trigger this before the tank is genuinely full — which is the case worth checking for if emptying the tank doesn’t clear it.

Working through it

Start by ruling out the simpler cause on the same troubleshooting line: inspect the floor tool, the wand, and the hose for a blockage first, since that’s listed ahead of the float valve in Numatic’s own table. If the motor note has genuinely changed pitch rather than just sounding muffled, that points at the float valve specifically. Check the recovery tank — if it’s full, that’s the whole explanation, and emptying it following Numatic’s own procedure resets the valve immediately. If the tank isn’t full and the valve is still tripping, the manual’s maintenance schedule lists cleaning and checking the float valve for damage as a daily task for exactly this reason — fouling on the float or housing can make it close early. One specific warning from Numatic’s manual is worth following to the letter: if foam or liquid is coming back out of the machine’s exhaust rather than being picked up, switch off immediately, let the liquid already in the power head drain back out through the exhaust, and check the float assembly seats and moves freely before using the machine again.

Verdict

Not a fault worth worrying about in the majority of cases — it’s the float valve doing exactly what Numatic designed it to do, and emptying the tank costs nothing. Worth a proper check of the float and its housing if it keeps tripping on a tank that genuinely isn’t full; a valve that’s stuck or visibly damaged after cleaning is the point where this stops being routine and is worth raising with a Numatic dealer rather than persisting with it.