In drilling, even the smallest tool can play the biggest safety role. The float valve (non-return valve) is one of them. Its mission: stop backflow of mud, cuttings, gas, or formation fluids into the drill string, protecting people, pumps, and the well itself.

Types of Float Valves
-Plunger Type (F): spring-loaded, durable, widely used in vertical and deviated wells.
-Flapper Type (G): hinged design, full-bore opening with less pressure loss, preferred in horizontal and high-angle wells.

Where Do We Put It?
The float valve is installed inside a float sub—a short drill collar or pipe sub designed to house it. The float sub is positioned:
-One or two joints above the bit in the BHA, ensuring immediate protection at the well’s lowest point.
-Sometimes higher up in the string (near jars or MWD/LWD tools) to provide an additional barrier, depending on well design and operational risks.

This strategic placement ensures:

• Backflow is stopped before it travels up the drill string.
• Bit nozzles stay clear during trips and connections.
• An extra well control barrier is always in place.

Takeaway: Though hidden inside a short sub, the float valve acts as a silent guardian – the first barrier of defense against unexpected flow from the formation.