World Plumbing Day

What the day is

World Plumbing Day is observed on March 11, established by the World Plumbing Council. The drainage side of the trade is covered on the Thomas Crapper entry; this one is about the supply side, which is where the risk sits.

Origin and background

Clean water arrives under pressure, and that pressure is the only thing keeping it moving in the intended direction. If mains pressure drops, through a burst main or heavy demand from a hydrant, the flow can reverse and draw water backward out of whatever it is connected to. A hose left in a filled bucket, a sink whose tap outlet sits below the waterline, or an unprotected connection to an irrigation system all become routes by which contaminated water is siphoned into the drinking supply. Documented incidents exist.

The defenses are simple and mostly invisible. An air gap, a physical vertical space between a tap outlet and the highest possible water level, cannot be defeated by pressure at all, which is why taps are set above the rim of a basin. Where an air gap is impossible, check valves and backflow preventers do the job mechanically. A great deal of plumbing regulation exists specifically to enforce this, and it is the main reason the trade is licensed: bad work here contaminates a shared supply rather than only the building it is in.

Stored hot water carries its own hazard. Legionella bacteria multiply in the temperature range roughly between twenty and forty-five degrees Celsius, which is why guidance keeps stored water above sixty and distributes it above fifty, and why a system left stagnant in an empty building needs flushing before use.

Lead service pipes also remain in use in many older areas, and replacement programs are ongoing in several countries.

How to take part

• Never leave a hose submerged in a bucket, pool or trough.
• Run the taps for a while in any property that has stood empty.
• Find out whether your incoming service pipe is lead, which utilities will often check.
• Know where your main stopcock is and check that it turns.
• Use a licensed plumber for anything touching the supply side.