FAQ: Backflow Preventers

Backflow preventers play a vital role in protecting the public from harmful contaminants in the water supply. It is essential to inspect backflow preventers regularly to make sure they are doing their job. But how do they work, and what happens during an inspection? We answer these and other common customer questions in this addition to our Services FAQ series.

First, the basics:

Q: What is a backflow preventer?

A: A backflow preventer, also referred to as a backflow or a cross connection device, is a device that only allows water to flow in one direction. Each building with running water draws its supply from a shared source, a system of pipes that are interconnected. In a neighborhood, these pipes may run water through houses, plumbing, yard irrigation, even home sprinkler systems. In a business or commercial area, it will be the source for the fire sprinkler systems, public bathrooms, water fountains, etc. As the water is being drawn to these individual sources, whether home or business, it goes through a backflow.

When a water main breaks or a pipe bursts, the system starts sucking water from wherever it can. If at the same moment a sprinkler system is watering a freshly treated lawn while the neighbor is filling a pot with water, that pot could become filled with chemical-laden water from the neighboring lawn. This is what the backflow prevents. It ensures that the water filling the broken pipes is not flowing back into the supply being used for the homes or businesses attached.

Q: Why did I receive a notice from the City saying my backflow needs tested?

A: The inspection of backflows is required annually, every 12 months. This requirement is enforced by the water companies working in tandem with the state. Water companies are required to show that every tap has a backflow that is being tested regularly. Contaminated water is a serious threat to the health and well being of those coming into contact with it. If a broken pipe or other issue in the water system causes there to be an issue, it is important that the state and the water companies be able to prove that if any water contamination reached customers, it was not their fault. By requiring the regular inspection of backflows and keeping these inspections recorded, the water companies and government protect themselves. If they remind their customers that their homes or businesses are due and they choose to ignore the reminder, then they are the ones responsible for their own damages.


Now, on to the specifics:

Q: My backflow was just repaired last year, so why isn’t it working now?

A: A backflow preventer is very sensitive to any type of foreign material in the water supply. A tiny piece of rust, galvanized coating, or any other debris can either become stuck or cut the rubber seal and cause the device to fail. This is why it is so important to have them inspected regularly.

Q: How come the City is only asking for proof of the backflow attached to my irrigation system?

A: The water that is issued to a house is separated: there is metered water that is used for sinks, toilets, etc. and unmetered water that is used for the home fire sprinkler system. The irrigation system for a house has a separate pipe that splits from the metered “house” water. The house has a backflow built into the water system and this backflow is not testable. However, the backflow connected to the irrigation system is different and can be tested. The water purveyor for the area in question can provide more specifics regarding testing/backflow requirements.

Q: When you come to test my fire line backflow will my water be cut off?

A: Typically, fire lines and domestic lines are separated before they reach the backflow preventers. Testing or repairing a fire line backflow will not affect your domestic water.

Q: My backflow is leaking externally from the bottom, so why are you replacing a different part of it?

A: The first valve in a backflow, the one that is closest to the water supply and that filters the water first, is called the #1 check valve. Due to its proximity to the supply it is extremely important. In a reduced pressure backflow assembly, there is a relief valve that discharges water to the atmosphere when the #1 check valve fails inspection, or “fouls”, meaning it is not functioning due to a clog or broken part. This is a fail-safe to stop water that is possibly contaminated from returning to the city water supply. It is highly possible that the relief valve is simply operating properly and what looks like a leak is actually this fail-safe in action.

Backflow preventors play a vital role in keeping the public safe by ensure the water supply is free of contaminants. If you have further questions regarding this important safety device or need to schedule an inspection, call your local Pye-Barker office today. We are always ready to assist with your fire and life safety needs!