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Old 01-12-2009, 12:40 PM   #1
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City water inlet shut-off valve?

looking behind the lavatory access panel, in 2008 classic 30' S/O

I'm told the valve (shown in 'open' position, just below water heater black control box) is the city water shut-off valve

Can somebody tell me what the brass fitting is that is bypassing it?
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Old 01-12-2009, 12:53 PM   #2
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I'm not an plumber nor do I play one on TV, but I'm thinking it is a backflow prevention valve.
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Old 01-12-2009, 01:11 PM   #3
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Shut off valve

That looks like PURE Airstream Rocket Science at work.

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Old 01-12-2009, 01:31 PM   #4
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Here's my guess at the theory. The backflow prevention valve does not allow "backflow" (surprisingly enough). I guess the rocket scientists were thinking that the owner should open to valve (plumbed parallel to the backflow prevention valve) to allow the system to be drained. So... why is this a bad idea (if indeed I'm right). If someone leaves the valve open, you have effectively defeated the purpose of having a backflow prevention valve.

Backflow prevention is a pretty big deal for municipal water systems. Trust me on this. My feeling is that there should be a system drain at the low point on the "user" side of the system. Of course, I will ready concede the point to any licensed plumbers in the crowd.
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Old 01-12-2009, 01:41 PM   #5
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if that's the case... you're saying the valve should be 'closed' at all times?.. except when winterizing (draining that portion of the water system)

IIRC, the manual says to only close the city water valve when winter camping...

btw- the manual states that the service faucet next to the city water inlet can be used to drain that portion of the water system when valve is closed...
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Old 01-12-2009, 05:41 PM   #6
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I'm in agreement that it's a check valve (back flow valve). I don't understand why it's installed in parallel & not series. Get rid of that loop & put the valve in line with the shut off. Mine is located in front of the shut off, but it will work behind it as well. It's purpose is to keep the water pump from emptying your fresh water into the public system should it's pressure become less than what's in your AS. It's not needed immediately, But put it in your " I'm bored & need something to do" list.
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Old 01-12-2009, 07:21 PM   #7
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The valved should be kept closed until you are going to winterize the trailer with antifreeze. With the valve closed, the "loop" with the check valve prevents water in the trailer from being sent back into the city lines.
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Old 01-12-2009, 07:33 PM   #8
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I discovered that valve the 2nd time I winterized. Didn't even see it the 1st time. So I looked at all the valves for the water heater bypass and this valve and it made no sense to me, but not being a plumber (though I've done a lot of it on houses I've owned), I figured "what the hell", so I opened it and water came out under the trailer below the valve—so I figured it drained something and that was what I was doing, so good!

Then, I did the bypass thing and wasn't sure when to return the mystery valve to it's original position, but waited until I had finished draining everything and closed it (I hope, so many valves….)

Glad to know others have this valve I didn't know existed and it was not something installed only in our Safari to confuse me.

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Old 01-12-2009, 09:36 PM   #9
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Most inlets have the check valve built into them. When I first saw the object in question, I thought it was a pressure regulator. I have one that looks very similar to that. I attach mine to the city water tap and attach the city water hose to that.

Just throwing out another possibility.
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Old 01-13-2009, 11:04 AM   #10
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Now that I looked at the photo blown up I get what you are talking about. I can now see the fitting which must be a check or one-way valve. My Safari is set up differently and I was talking about a valve next to the water heater below the 3 valves for the water heater bypass. I do not recall that valve having a bypass around it, but I don't understand what the bottom, 4th valve, is for, except to drain something. I don't think it's mentioned in the literature, at least in the part about winterizing.

All these valves are accessed from an exterior door at the front curbside of the trailer. That door is next to the water heater metal door. The water heater has the usual drain plug on it. When I winterized I just reversed the 3 bypass valves. Then I noticed this 4th valve below all of them. I hadn't noticed it the year before because all I was looking for was the 3 bypass valves and I thought all the other drain valves were on the other side of the trailer.

I opened it and water came out below the trailer. I didn't really think a lot about it at the time. Maybe there is some similarity between this valve and the one shown in the photo.

I'm unsure how pressure regulators got involved in this thread. I think I read somewhere Airstreams come with an internal pressure regulator, but we still use our own because I can't remember where I read there actually was one. Now we put it on the faucet (before the hose) in case water pressure is so high it blows the hose apart. A campground owner in NE Oregon warned us of 120 psi water from the water system in that town and many blown hoses.

There's got to be a check valve somewhere to prevent the city water and internal fresh water systems from getting "confused", but I don't know where it is in my trailer. I would imagine it's near the water pump. I seem to remember the water pump can be used to boost poor city water pressure, but I don't know how it wouldn't then pull water from the fresh water tank. If the apparent check valve in the photo is to prevent mixing the city water and fresh water systems, then the hand operated valve in front would have to be closed during normal operation and thus it must be for draining something.

I keep thinking about figuring out my plumbing system, but haven't been bored enough to do so. It seems the systems can be really different in different trailers.

I have the distinct feeling that by now I'm babbling and my computer should be taken away from me.

Gene
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Old 01-13-2009, 12:01 PM   #11
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here's all I can find about it in manual:
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Old 01-13-2009, 12:08 PM   #12
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I think it's a backflow prevention valve, not a pressure reduction valve. Most pressure reduction valves have a different appearance (bell shaped lump).

In general, there should not be any valve or pipe configuration that would prevent the backflow prevention valve from doing its job. Haved it plumbed in parallel rather than in series just seems like a bad idea. Now, I agree that a pressure reduction valve is a good idea, and "Code" in some areas. I think a backflow prevention valve is an absolute necessity. It depends where you are, I suppose, but normally I see pressure reduction valves first (after the first valve) followed by backflow prevention. If you want whole trailer filtration, I'd install that next. Just my thoughts.
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