Perhaps it is the fact that I like eggs that I came up with this analogy for "learning."
Sooner or later we all have to come face to face with discovering that something we thought was true, either is not true, or is not true anymore.
This particular bit of egg on my face is about outside faucets. There are lots of things to think about regarding outside faucets for an inspector, but this post is only about “Anti-siphon” devices, and whether they are present on the valve or not. If it is newer construction the inspector will note if they are missing or present--and any conditions associated with them that might be observed.
Typically in older homes it might be appropriate to recommend that the devices be added or that newer style valves be installed in the context of overall repairs to the plumbing.
What these devices do is protect the swimming pool water that the kid has just peed in (or worse), from being sucked back into the house water supply if the flow of water were to reverse. There are several conditions that can allow this to happen, such as flushing water mains/hydrants at the street, or even running faucets on the opposite side of the house. Regardless of the science of how this happens, they are required by current plumbing codes.
Back to the egg on my face.
Historically I have only looked for, or known about, two types of anti-siphon devices for outside faucets. One is connected on the place you connect the hose to like in the following picture.
The other is mounted on the top of the valve like the one in the following picture with its protective cap missing.
Recently I found the following valve that did not have an anti-siphon device at either of the usual locations but it did have this interesting, albeit embarrassing, tag.
This tag told me that there is a third way to accomplish the requirement for a vacuum breaker--and it is built into the valve itself. It also made me aware that I likely mistakenly called for installation of anti-siphon devices on some valves where I mistakenly thought they was "missing."
My first reaction was, “Well what if someone cuts the nice informative tag off?” The clue is in the valve stem that the handle attaches to. There is a small hole present in the stem (like in the next picture) and that is where the faucet will draw in air if the valve goes under negative pressure.
While I had to deal with the egg on my face, I am just grateful there is at least a way to identify a valve that has this type of anti-siphon device. Also with a proper outside faucet I can sucessfully wash the egg off my face.
Charles Buell, Real Estate Inspections in Seattle
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WA State, Home Inspector Advisory Licensing Board