The Homeowners Guide To Backflow Prevention

It’s a nightmare image: brown, smelly water flowing up through your drains and into your sink. Backflow is unpleasant, unsanitary and, honestly pretty disgusting. Luckily, it’s also fairly rare, thanks to some ingenious plumbing solutions.

If you do find yourself in the situation of having to deal with water rising up from where it shouldn’t, understanding what’s going on is vital.

Understanding Backflow

Backflow is, as the name suggests, the unwanted flow of water in the opposite direction. This could happen within your homes plumbing system or come from the municipal sewers. Either way, it’s a bad thing, says Dennis Property Management company.

There are two mechanical causes; back pressure and back siphonage.

Back Pressure : Back pressure occurs when the pressure within the system is higher than is found in its supply.  This means that the water will be forced into system. This is most common in unvented heating systems where thermal expansion of the water increases the pressure.

Back Siphonage: Back siphonage is the reverse. If the pressure within a system is lower than its supply, the water will seek to fill that gap. This is most common when supply is interrupted or the system is drained.

Consequences of Backflow

Backflow has some pretty serious potential consequences.

Chief amongst these is the risk to health. Much of our home’s plumbing system is devoted to getting dirty, soiled water away from us safely and cleanly. When this process reverses, the health risks are obvious.

On a grander scale, there are significant risks to the environment too. In effect, a city’s sewers or a home’s septic tank are just large-scale plumbing systems. If waste water, including human waste, isn’t directed safely to where it should be, contamination will occur.

Backflow Prevention Methods

Whether in the home or the municipal sewage system, there are systems in place to avoid backflow. A number of ingenious devices and techniques are employed to keep water flowing in the right direction.

Check Valves

Check valves, also called non-return valves or reflux valves, are generally small, simple and inexpensive. They work automatically to allow the flow of water in one direction and block it in the other.

They come in a few varieties but the most common are:

• Ball check valves: These contain a small ball which is pushed out of the way when water is flowing in the right direction. If the flow reverses for whatever reason, the ball is pushed into a thinner section of the valve, blocking it.
• Swing check valve: These are normally held closed by the pressure of the water within the system. An example common in most homes is the flapper found in your toilet cistern.

You may also come across lift-check valves, in-line valves in the home. They both work in a similar manner, allowing water through one way but blocking the other. There also might be a stop-check valve in your home. This works like the others but with the added advantage of an additional manual control.

Air Gaps

Within your plumbing system, there are areas which are purposefully not filled with water. The most obvious example is that your faucets are above the drain of your sink. Slightly less obvious are things like:

• Float valve outlets being above the overflow level.
• Shower hoses being fixed to avoid the head dropping below the water level in a bath or basin.
• Tundishes consist of a spout and a funnel. This allows an airgap and can be found in some overflows.

These gaps are generally regulated by local building codes.

Reduced Pressure Zones

A reduced pressure zone device (RPZD RPZ or RPZ valve) prevent both back pressure and back siphonage. They consist of two check valves with a pressure monitored chamber (the ‘zone) between them. The Zone is kept at a lower pressure than the supply but still strong enough to be useful within your home. This reduced pressure is maintained by differential pressure relief valve.

Their main advantage over single valve systems is that you can easily inspect them to ensure that at least one valve is functioning properly. By checking which is failing, you can gain insight into what is happening.

They’re most commonly used on larger scale systems but they can be employed wherever there’s a risk of serious contamination.

Regulations and Compliance

With the potential risks to public health, it’s no wonder that backflow is strictly regulated. Wherever you happen to be, local building codes will require certain devices and considerations when designing your plumbing.

In Massachusetts, for example, the local Department of Environmental Protection enforces a strict set of checks and regulations. Chapter 111, Section 160 A of the Massachusetts General Law, enacted as far back as 1960, and other regulations set out strict guides to which devices must be installed in a variety of settings.

In Rhode island, similar regulations spell out in great detail what your legal requirements are.

Both require installation by licensed plumbers who will know exactly how the rules apply in any given situation.

Maintaining your Backflow Prevention System

Naturally, back flow prevention systems require a certain amount of looking after. With the potential health hazards associated with a failed system, it’s best to keep on top of it.

It’s a good idea to schedule in a yearly inspection to ensure that everything is working as it should. The inspector should be certified and experienced and should give you a detailed report. They’ll inform you of worn parts and damage that might not be an issue at the moment but may be in the future too.

It’s also a good time to keep up with the general upkeep. They can replace worn and broken parts and flush the system to remove sediment build up.

Outside this yearly schedule, it’s a good idea to keep an eye on your plumbing. At any sign of a leak, strange noises or any other unexpected change, get a pro in to take a look.

Through clever use of a few simple devices and plumbing techniques, your drinking and waste water should never meet.