Understanding Back Siphonage In Plumbing Systems

As an engineering student or engineer, you know how important it is to design and keep plumbing systems that are safe and work well.

But there is one very important thing that is often forgotten: back siphonage.

This happens when water that has been contaminated or polluted is put back into the main water supply.

This could be very bad for people's health.

Back siphonage is a problem that can happen in any plumbing system, and it is your job as an engineer to make sure it doesn't.

In this blog post, I will talk about what causes back siphonage, what its risks might be, and, most importantly, how to stop it from happening.

By the end of this article, you will know everything you need to know about back siphonage and how to keep your plumbing safe and secure.

So, let us dive in!

Understanding Back Siphonage

Formal definition:

The flow of used, contaminated, or polluted water from a plumbing fixture or vessel into the pipe that feeds it is caused by reduced pressure in the pipe.


The siphoning of part of a plumbing system caused by the failure of mains water pressure.


Backsiphonage and backflow are two different things that can happen in plumbing systems that can cause drinking water to become contaminated.

How does backsiphonage work?

Backsiphonage is when water flows backwards in a plumbing system because of a vacuum or low pressure in the supply pipes.

It is like drinking water through a straw, and it can happen when the water supply is cut off because of nearby firefighting, repairs or breaks in the main, more people using water in one place, or pipes that are too small.

Backsiphonage can bring harmful substances into the drinking water, making it unsafe to drink.

A backflow prevention assembly must be put in place by a plumber to stop backsiphonage.

This assembly, which is also called a "backflow preventer," keeps dirty water from flowing back into the potable water supply.

It does this by acting as a barrier between the potable water supply and the dirty water.

Domestic and fire assemblies are both types of backflow preventer assemblies.

What does backpressure mean?

Backpressure is another type of backflow that can happen in any pressurized system, like chemical feed pumps, boilers, elevated tanks, or recirculating systems.

When the pressure of the water downstream is higher than the pressure of the water coming in, this is called backpressure.

If the supply pressure drops below the required level, this difference in pressure can cause dirty things to flow into clean pipes.

Preventing Backsiphonage and Backflow

To keep the potable water supply safe, it is important to stop both backflow and backsiphonage.

This can be done by putting in backflow preventer assemblies, which act as a barrier to stop contaminated water from flowing back into the supply system.

It is also important to test and maintain backflow preventer assemblies on a regular basis to make sure they are working properly.

A plumber can do these jobs and make any repairs or replacements that are needed.

Back Siphonage: The Shocking Truth About Contaminated Water in Your Pipes

Still hard to understand? Let me change the point of view a bit:

Are you sick of clean water coming out of your faucets? Are you sick of knowing that when you turn on your faucet, you are not getting a healthy dose of bacteria? Do not worry, though, because back siphonage is here! That is right, forget about having clean and safe water.

With back siphonage, you can get all the dirty and contaminated water you want, all because the pressure in your pipes is lower.

Who needs clean water to drink when you can enjoy a nice cup of back siphonage?

Okay, jokes aside, back siphonage is a real problem that can be very bad for your health.

We continue talking about what back siphonage is, how it happens, and, most importantly, how to stop it.

Health Risks and Common Causes

Back siphonage can be very dangerous to public health because it can lead to drinking water in plumbing systems getting dirty.

Common Causes of Back Siphonage

Some of the most common reasons for back siphonage are:

  • A break or repair in a water main that stops the flow of water.
  • More people needed in one place, like fire fighting.
  • Pipes that are too small.
  • Positive pressure from a partial vacuum or vacuum in the supply pipes.

Backpressure is when the pressure of the water coming out of the pipe is higher than the pressure of the water coming in.

Backflow and Cross-Connections

Backflow events happen when the flow of water is turned around and water flows into a system that should be closed.

Most of the time, this happens when the system loses pressure and the resulting vacuum draws water from the outside.

There is a risk with every connection, and cross-connections can let contaminants into the drinking water system.

To stop this, the public needs to be taught about how cross-connections and back-siphonage can cause contamination.

Health Risks Associated with Back Siphonage

Cross-connections and backflow events that are contaminated can pose a number of health risks.

These risks could come from anything in the environment that could be introduced, either by accident or on purpose.

Some of the most common health risks of back siphonage are the following:

  • Gastrointestinal illnesses.
  • Rashes and infections on the skin.
  • Infections of the lungs.
  • Infections in the eyes and ears.
  • Effects on the brain.

Causes of Back Siphonage and Backflow

Back siphonage happens when low or negative pressure in the supply pipes creates a vacuum that lets water flow in the opposite direction.

Most of the time, back siphonage is caused by:

  • The water main is broken.
  • An increase in demand in one place, like firefighting.
  • Pipes that are too small.
  • There is a vacuum or a partial vacuum in the supply pipes.

Prevention Methods

Prevention Methods for Back Siphonage in Plumbing Systems

Back siphonage can be stopped in plumbing systems in a number of ways, such as with air gaps and atmospheric vacuum breakers (AVBs).

But it is important to remember that different methods need to be used together for the best results.

Some other ways to stop something from happening are:

  1. Backflow prevention assemblies (BFPA): These special valves keep dirty water from flowing back into the potable water system.
  2. Check valves are one-way valves that only let water flow in one direction. This keeps water from being sucked backwards.
  3. Maintaining the right pressure in the water supply: If the pressure in the water supply system stays the same, there will not be any negative pressure to cause back siphonage.
  4. Plumbing systems should be inspected and maintained regularly.

This helps find any cross-connections or other problems that could cause back siphonage.

It is important to have licensed plumbers install and check all backflow prevention devices to make sure they are in line with local laws and rules.

Homeowners should also be responsible for protecting their drinking water system by preventing or fixing any cross connections on their property that connect to the plumbing water supply system.

Prevention Methods for Back Siphonage in Laboratory Settings

Backflow preventers are the best way to stop back siphonage from happening in a lab.

These devices are put in the pipes that bring water to homes so that contaminants do not get into the water supply.

Backflow preventers work by breaking the vacuum that is made when water flows backwards and letting air flow into the system upstream of the check valve.

To stop back siphonage, you can also physically separate the potable water source from any other sources of contamination.

Cross-connection control should be in place at all times in laboratories to make sure that potable water supplies do not get contaminated or polluted.

This includes testing all double-check valves and devices in low-pressure zones once a year and having the manager check them out right after they are put in.

Prevention Methods for Back Siphonage Using Air Gaps

The easiest way to stop backflow and backsiphonage is with an air gap, which is also thought to be the most effective.

A vertical space between a water outlet and the highest level of a possible source of fluid contamination is called an air gap.

An air gap is a way to keep water from flowing backwards that has nothing to do with mechanical parts.

An approved air gap should be at least double the diameter of the supply pipe, measured vertically above the overflow rim of the vessel, and should never be less than 1 inch.

When it is properly installed and taken care of, an air gap works as described above.

It stops drain water from being sucked into the potable water system.

But it is important to keep in mind that air gaps stop the flow of water and cause the pressure to drop.

So, putting an air gap in every plumbing fixture might not be a good idea.

In some cases, you may need mechanical backflow preventers like pressure vacuum breaker assemblies, reduced pressure assemblies, hose bib backflow preventers, double-check valves, or barometric loops.

It is important to be proactive about plumbing safety by putting an air gap or a backflow preventer valve in places where clean water is most likely to get contaminated.

The consumer is responsible for keeping the water system on their own property from getting dirty.

In conclusion, stopping back siphonage is important to keep potable water safe and of good quality.

Back siphonage can be stopped and the water supply kept safe by using a mix of different ways to stop it, as well as regular inspections and maintenance of plumbing systems.

Water Animation – Backsiphonage

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Places that should be more careful

BusinessesBack siphonage is more likely to happen in commercial buildings like hospitals, schools, and restaurants because their plumbing systems are more complicated and they use chemicals and other pollutants a lot. Back siphonage can be stopped in these situations by putting in backflow preventer valves or air gaps.
Industrial FacilitiesManufacturing plants and chemical processing plants use a lot of water and chemicals, which can lead to back siphonage if the right safety measures are not taken. Backsiphonage can happen in these situations, so backflow prevention devices must be put in place and checked and fixed regularly.
FarmsBack siphonage can also happen in agricultural settings, especially when pesticides or fertilizers are added to irrigation systems. Farmers can stop back siphonage by using backflow prevention devices or by using other types of irrigation, like drip irrigation, which is less likely to happen.
LaboratoriesBack siphonage can happen in laboratories that use chemicals and other dangerous materials. This can make the water supply dirty and pose a serious health risk. In a lab setting, backflow prevention devices must be put in place and strict protocols must be followed to make sure that dangerous materials are handled safely.


In conclusion, back siphonage is a serious problem that engineers and plumbers need to pay close attention to.

By knowing what causes back siphonage and taking steps to stop it, we can make sure that our plumbing systems are safe, work well, and do not expose us or anyone else to harmful contaminants.

But back siphonage is also a good reminder that the systems we build have a big effect on the health and happiness of the people who use them.

As engineers, it is important to think about what our work means in the real world, not just how it looks and how it works.

By doing this, we can come up with solutions that not only meet our technical needs but also help people and the environment.

So, the next time you work on a plumbing system, remember that it is not just a technical project; it is also a chance to make a difference in the world.

Let us think this way about our work and come up with solutions that help us all.

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