How Does a Backflow Preventer Work

25 September 2014

Backflow preventers are a handy little piece of gadgetry that can prove to be indispensible for residential, industrial and commercial water supply lines. Backflow preventers are used in all types of places like gardens, farms, and even for residential areas that store or otherwise employ free-flowing water. In other places such as farms and communes, where the source of water is often taken from a natural area such as a river or a stream and employed for irrigation and sundry other purposes, the risk of backflow is ever-present. This makes backflow preventers very important, as they are a line of defense to protect the sanitation of an area’s water-supply.

To prevent the water supply from being contaminated, backflow preventers are often installed in plumbing systems. The science behind backflow preventers is actually quite simple, and the technology has been around for as long as civilizations started to practice large-scale agricultural feats. But how does a backflow preventer work?

How does a Backflow Preventer Work – The Science behind Backflow Filters

In a nutshell, backflow preventers are installed in order to prevent supplied water from being contaminated by water that is backed up from wherever the flow is directed too. How does that happen? This situation can occur, when the backflow flow is strong enough and the water backlashes into the primary water source, often muddying it or otherwise placing it at risk for possible contamination. In order to prevent this from happening, a backflow filter is installed.

These are typically ball check valves, which comprise of a ball, usually made of non-corrosive metal, plastic, or some other non-reactive substance that is employed as a means to block the backlash of water from entering into the main water valve. It typically performs two functions:

Letting water out – Because the ball check valve is often of just the right size to effectively spin when water is pushed outward, it efficiently lets water out in an easy ad controlled stream. It is kept in place through the use of a spring which keeps it shut, unless water is ejected into the supply line. When the water pressure is strong enough, the ball is then pushed back from the opening, thereby allowing water to pass through unimpeded.

Some ball valve models even purposely make balls that are only about several diameters larger in order for the mechanism to stay in place, and at the same time prevent even the minutest of particles from passing through.

Keeping Water Out – In the absence of projected water pressure, the ball immediately closes, shutting off any possibility of water entering into the main supply line. In the event of water being projected outward with backflow trying to rush inward, the projected water will flush out any inward influx, while the outward push of water from the outside of the valve will immediately force the ball into a closed position, shutting off the mechanism entirely, allowing no water to go either in nor out.

For more information on how does a backflow preventer work and the other types of backflow preventers available for residential, industrial or commercial use, please visit:

The Best Brand in Plumbing – G. Brand & Sons

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