Noisy vacuum breaker valve

[born2camp]

Makes a siphoning/whine type of noise only when I use the hot water. Once the water pump has the system pressurized again it stops the noise. Is it about to go out? There are no leaks just the noise and it is just in the last 2-3 trips that it began doing this.

[Gary RVRoamer]

Where is this vacuum breaker? Most RVs do not have one in their internal plumbing - a vacuum breaker (anti-siphon valve) is usually on the city water connection on the site.

The noise occurs when the valve is admitting air to break a siphoning action. After the water line pressurizes, the poppet valve inside is forced closed by the water pressure and the noise stops. In other words, it is a normal sound. Not sure why you just started hearing it, though. Did you change something in your city water connection equipment? Or maybe you've been going to a different campground?

[born2camp]

We mostly boondock so it is not hooked up to city water. On my coach it is in the rear vanity sink under the counter. Pretty much right above the hot water heater. Never hear it when running cold water, but turn the hot water on (any faucet) and I can hear it until I shut the hot water faucet off and system pressurizes/pump shuts off.

[JerryForwood]

Quote from RV Roamer:
"Where is this vacuum breaker? Most RVs do not have one in their internal plumbing - a vacuum breaker (anti-siphon valve) is usually on the city water connection on the site."[/quote]

Sorry but almost all RV's have what he is talking about. You will find them attached to the drain lines, usually tucked up behind the kitchen or bathroom sink. Look behind yours. I'll bet you will find at least one in your coach as well. They are used to allow the intake of air while draining the sinks but not allowing the sewer gases to enter your home/MH. It makes it so that you don't have to run as many vent pipes through the roof. I can't remember the proper name for them right now, its not a vacuum breaker. But I guess I'm just in the middle of a senior moment.

[RV Wizard]

Are you sure it is not the check valve on the water heater? The symptoms of what you are discribing does not sound like it is the vacuum breaker in the drain line but the check valve on the water heater hot and/or cold water connections.

[Hyall]

Stutor vent for the waste line so you don't have to penetrate the roof for venting, Some water heaters have backflow preventer or vacuum breakers to prevent siphoning of the tank to prevent element burnt out if drain dry

[bldrbob]

I also think it is the check valve.Try running hot water in other sinks.
BOB

[Dick Osterhof]

There is a check valve in the system, near the water heater, to prevent back flow of hot water into the cold water. The check valve is a safety item. It is spring loaded and under low flow conditions will chatter, thus the buzzing sound. Not a problem!