What Needs Backflow Protection
A property has more connections to the water supply than most people realize, and they are not equally dangerous. A hose lying in a flower bed is one kind of problem. A cooling tower or a chemical injector is another kind entirely.
Find the connection you are asking about below. Each one explains what the hazard actually is, what level of protection it usually calls for, and what we do about it.
If you are trying to identify a device you already have rather than a connection, start with the device types instead.
The most common backflow connection on any residential property, and the reason most homeowners have an assembly at all. The risk is not the water you put in — it is the fertilized, sprayed, animal-walked soil the heads are sitting in when pressure drops.
The outdoor tap is the most-used cross-connection on most properties and the one nobody thinks about. A hose in a flower bed, a sprayer with chemical in it, an end sitting in a stock tank. Protection costs almost nothing. Most properties built before the code required it do not have any.
One assembly on the service line, protecting the public main from everything inside the building. That is containment — and it protects the street, not the drinking fountain down the hall. What is inside the building decides whether containment alone is enough.
Stock tanks, waterers and ag supply lines are health hazard connections and are treated that way. A float valve sitting in a tank animals drink from is a direct path. On the Western Slope there is a second wrinkle: a lot of ag property has both domestic and ditch water, and where those two can meet is the whole point.
A fill line from the building supply into standing surface water — algae, fish, landscape runoff and whatever the wildlife adds. A recirculating pump means it can push, not just siphon. The usual failure is a fill line somebody added later and never protected, because nobody thought of it as plumbing.
A large volume of chemically treated water with a permanent connection to the house. An automatic fill is not a hose somebody remembers to disconnect. The cleanest answer is often an air gap, which is not an assembly at all and has nothing to test or fail.
An injector changes what the system is. It stops being a line full of yard water and becomes a line full of concentrate — a health hazard, with the injection equipment itself able to push. If you are thinking about adding one, price the assembly before the injector. It is frequently the larger number.
Water that has stood in steel pipe for years, sometimes with antifreeze or foam in it. Fire systems are one of the few connections where backpressure is a given rather than a possibility — a standpipe has elevation behind it and a fire pump has far more. The fire marshal and the water provider both have a say.
More cross-connections than any other room in a building — dish machines, pre-rinse sprayers, carbonators, ice machines, mop sinks, steam equipment. They are not equally risky, and one of them can put dissolved copper in the drinking water. Kitchens are protected at several points, not one.
A connection between the building supply and a closed loop of hot, usually treated water. Whether it is a health hazard depends entirely on what is in the loop — and a system that gets treated later without the assembly being reconsidered is a real and common problem. Boilers generate backpressure by design.
An open basin of warm water, exposed to air, dosed with biocide to stop it growing things. Every part of that is a reason to keep it out of the drinking water. Add circulation pumps and you have health hazard plus active backpressure — the clearest case in this whole list.
The highest-consequence category in cross-connection control. Chairs, aspirators, autoclaves, sterilizers, analyzers and lab sinks all connect to the building supply, and much of it is pumped. These facilities are protected at the service line and again at each piece of equipment, and the inventory runs long.
A car wash, a machine shop coolant loop, a plating line — the hazard depends entirely on the process. What they share is water that has been used for something, is often dosed, and is nearly always moved by a pump. Process lines also change, and a new chemical step changes the classification whether or not anyone tells the provider.
The connections most likely to be missed, because nobody thinks of a hydrant meter or a construction hookup as plumbing. A water truck, a temporary service, a food truck, an event connection — something unknown attached to the public main, usually with a hose. Worth asking about before the connection, not after.