What Causes Backflow in Plumbing?

Backflow happens when the water comes out of one drainage pipe and goes back into the other. The hot water that usually goes out through a kitchen sink or bathtub drains back down and enters the cold water in a cold-water supply pipe. If you have an indoor sprinkler system, backflow can happen if someone turns on a faucet or starts using an air conditioner connected to your main line for cooling.

Backflow is a problem if it is not spotted in time. The pressure of the water entering the hot-water line can burst, causing water to spill all over your basement or washing machine. It can also cause the temperature of the water to rise, which can be dangerous if anyone flushes a toilet or takes a bath. Here’s what you need to know about backflow, its causes, and how you can prevent it.

Contact for Service

Types of Backflow in Plumbing

There are two main types of backflow — backpressure and back-siphonage:

  • Backpressure: Backpressure occurs when excessive pressure from the main line or a poorly placed pump causes internal backflow, where water reverses into the household system. This often happens if a hose bib or faucet is turned on without being opened first. External backflow can also occur, such as when cleaning products or dirty water are improperly disposed of down the drain, allowing water to reenter through sinks or bathtubs. This issue is more prevalent in rural areas lacking separate storm-drainage systems.
  • Back-siphonage: Back-siphonage is a backflow problem when water from a separate drainage system enters the household plumbing. It commonly happens in rainwater systems. It results from secondary backflow, which occurs when water comes back through the wastewater treatment process and into your drain. It can occur if your home’s plumbing is connected to a water recycling system that goes directly to the toilet or if you use a laundry machine that recycles for its greywater source. Minor blockages can also cause sewerage pipe damage. These blockages can occur in the underground pipe or the utility hole.

Signs You May Have a Backflow Problem

Recognizing the signs of backflow issues early is key to maintaining a safe and healthy water system. Here are some common signs that you may have a backflow problem:

Discolored or Foul-Smelling Water

One of the most noticeable signs of backflow is water that appears discolored, often yellow, brown or cloudy. This discoloration usually indicates the presence of contaminants like dirt, rust or even sewage that may be entering your clean water supply. In addition to discoloration, foul odors, such as a sulfur-like or sewage smell, can indicate a backflow issue.

Changes in Water Pressure

A sudden or unexplained drop in water pressure can signify backflow. Backflow disrupts the normal water pressure, which may lead to lower pressure in your faucets, showers and other water fixtures. If you notice a significant decrease in water pressure, especially when multiple fixtures are being used, it could indicate a backflow problem that needs to be addressed.

Unusual Noises in the Plumbing

When you turn on a faucet or flush a toilet, backflow can cause air pockets in the plumbing system, producing gurgling, banging or bubbling sounds. While plumbing noises can result from various issues, persistent or loud noises may indicate backflow.

Health Symptoms

Contaminated water can lead to health issues such as stomach cramps, nausea, diarrhea and other gastrointestinal symptoms. If multiple household members experience these symptoms without a clear cause, it may be worth investigating a backflow issue as a potential source.

If you suspect a backflow problem, promptly contact a licensed plumber or water system specialist. They can perform tests to confirm backflow and address the problem with solutions like backflow prevention devices. Preventive measures and regular inspections can also help ensure your water supply remains clean and safe.

Causes of Backflow in Plumbing

The following are the main events that can cause backflow to happen:

1. A Broken Water Main

If you have a broken main, the system may not be able to deliver enough water to keep up with demand. The system may also leak, which can cause leaks in your house or even sewage to pour into your basement. You may also hear loud squeaking or popping sounds when you rinse dishes in the kitchen sink, and there are no drains clogged with food and other debris.

2. Prolonged Power Breakdown

An extended power breakdown is another major backflow event to watch out for because it can lead to the growth of bacteria in your system. Water in a storage tank can stagnate, which allows bacteria to grow. If this happens in the hot water tank, it can cause an eruption of scalding hot water when you try to take a shower or bath. It is also important to note that hot water systems have small electric pumps that circulate water through the pipes.

3. Plumbing Overhauling

A plumbing overhauling can lead to backflow because the water is not draining out of the system. It is especially true if you have an older home that has been fitted with new pipes and fittings that are different than the previous pipes.

4. In-house Pressure Difference

If there is water from the main line in your home and you cannot turn on a sink or bathtub faucet without causing a backflow, then there is an in-house pressure difference. Note that this is different from the pressure caused by a broken main, which is the amount of pressure from both the main line and the tank.

Potential Sites of Backflow

Below are some of the common sites that can lead to backflow:

1. Bathroom Faucet

If a bathroom faucet is leaking, it may cause water to flow back into the cold water line. The bathtub and sink water in your toilet may become contaminated. To fix the problem, you should either replace or repair the faucet. You should also inspect the pipes for signs of corrosion and fix any leaks found.

2. Clogged Drain or Sewer

The blocked water can go back into the plumbing if you have a clogged drain. It is more common in older homes that use pipe traps. If you want to fix this, you can use a drain snake or a chemical drain cleaner. Note that a clog in your sewer line can also cause backflow problems. If you suspect this is the case, call for professional assistance to fix it.

3. Outdated and Damaged Fittings

If an outdated fitting or damaged pipe is in your home, it may not be able to remove all the water from the plumbing system. If this happens, you might end up with backflow in your toilet or shower, so it’s essential to schedule an inspection when you notice this happening.

How to Prevent Backflow in Pipes

Preventing backflow in pipes is needed for maintaining a safe and clean water supply. Here are several effective methods to prevent backflow and protect water quality:

1. Install a Plumbing Backflow Device

One of the most reliable ways to prevent backflow is to install a backflow prevention device. Common types include reduced pressure zone (RPZ) valves, double-check valves and vacuum breakers. These devices stop water from reversing direction, keeping contaminants out of your clean water supply. Consult a licensed plumber to determine the best device for your system and ensure it is installed properly.

2. Schedule Regular Testing and Maintenance

Backflow prevention devices require regular testing and maintenance to function effectively. Routine maintenance and testing can detect problems early, allowing for timely repairs that help avoid potential contamination. 

3. Maintain Proper Air Gaps

An air gap is a vertical space between a water outlet, such as a faucet, and the highest point of the water source. These gaps help stop backflow. Ensuring adequate air gaps in fixtures such as sinks, dishwashers and washing machines is a simple yet highly effective way to prevent backflow. Check for proper air gaps in all key areas, especially where hoses or pipes might cross with contaminated water sources.

4. Be Mindful of Water Pressure

Avoid situations that cause sudden drops in water pressure, as these can increase the risk of backflow. For instance, high water usage across multiple fixtures can sometimes cause pressure fluctuations. Managing water usage and addressing low-pressure issues promptly can help reduce this risk.

How to Fix Backflow in Plumbing?

There are two main ways that you can deal with a backflow problem: air gaps and backflow prevention devices. You can install air gaps on sinks, tubs, and toilets. They are easy to install and require no additional equipment other than the pipe. In a plumbing system, potable water and wastewater are intended to flow in opposite directions to prevent contamination. The air gap is a one-way valve, meaning water can only flow from the potable side to the waste side of the fixture. It also prevents gases from flowing from the waste to the potable water side of a plumbing fixture. Air gaps are easy to maintain and do not require annual inspections, making them very cost-efficient.

You can also utilize a backflow prevention device, which is used to prevent the contamination of potable water sources in your plumbing system. Check valves and vacuum breakers are the most common types of these devices. Backflow prevention devices control the direction of water and are usually installed where plumbing fixtures connect to the main drain line. They should not be confused with back-siphonage preventers used for wastewater applications. There are different types of backflow prevention devices, including:

  • Pressure Vacuum Breaker Assembly
  • Reduced Pressure Backflow Prevention Assembly
  • Spill-Resistance Pressure Vacuum Breaker Assembly
  • Double Check Valve Assembly

Our professionals at IT Landes Home Service Team in Harleysville, PA, can help you choose the right one for your needs.

Contact the Professionals

An important thing to note is that backflow does not only apply to plumbing systems. It applies to many other industries, such as water and air flow systems. At IT Landes Home Service Team, we provide home, commercial, and industrial plumbing and HVAC services, including design, special projects, maintenance work, installations, and repairs for clients in Montgomery and Bucks Counties. Contact us today to schedule an appointment with our friendly and experienced technicians.

Contact Us

Previous ArticleShould You Choose Multizone AC for Your Office Building? Next ArticleWhat Is An AC Capacitor and Can I Replace Mine