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KerriO · 08-24-2011, 12:47 PM

So I'm thinking we have an obstructed vent pipe for our grey water tank. The monitor went from nearly empty to flashing red overnight last night, and when I looked down the shower drain, I could see standing water pretty high up. No way we used that much! We didn't even use the shower.

We drained some into a five-gallon tub. It filled the tub, but then turned to a trickle after that (with the tank still mostly full).

I can't find any info on where to look for the vents, or what they even look like. The manual doesn't even mention them.

I have a 2008 International 27FB.

Sphere Guy · 08-24-2011, 12:54 PM

There should be water down the shower drain held in the "P" trap. The shower / sink vent in my 2008 safari is under the rear sink, and does not vent thru the roof like the black tank vent.

Is the grey tank monitor working? after draining into the tub, u didn't say hiw big of a tub, it should register on the monitor. Question the monitor if it showed full overnight.

KerriO · 08-24-2011, 01:07 PM

Based on what I've read elsewhere on the forum, you can look down the shower drain directly into the tank. This isn't true?

I said the tub was five-gallon. We definitely didn't drain enough to empty the tank before it started trickling.

I would assume that the vent locations might be really different on a 23' vs a 27' FB…

Our monitors are far from accurate, but they generally are *somewhat* in range. EG, if it's red, it might be slightly less than half full; if it's flashing red, it may be nearing full, but not *that* full. I am relatively certain, regardless of what the monitor says, that we've still got water in the tank that didn't drain. For what it's worth, the monitor went from flashing red to solid red after the five-gallon emptying.

Silver Goose · 08-24-2011, 01:21 PM

I really think you are looking down at the standing water in the trap. Without a trap, you would be smelling the grey tank, not nearly as potent as the black, but you wouldn't like it. The black and grey tanks should each have a vent pipe to the roof. Do you not see 2 up there? The sinks often have a device that I believe is called a vacuum breaker. It's a 1-way rubber flap that allows the sink to flow freely into the tank.

You can normally look straight into the black tank when you hold the flush valve open on the pot.

KerriO · 08-24-2011, 01:26 PM

I was probably misinformed (or I mis-read) about being able to look into the shower drain. Regardless, I still think there's more water to be drained. (And I'm bummed that there's not a simple non-monitor way to check that gray water level!).

I guess we'll need to get the ladder out, because I can't see any vent pipes from here. (I assume their location on the roof would be somewhere directly over the tank's location?). There is something with a conical black plastic cover, that is maybe 8" in diameter, and not very tall. Is that the vent pipe? I just have no idea what I'm supposed to be looking for.

Sphere Guy · 08-24-2011, 01:35 PM

That might be it KerriO, or the black tank vent. But they may be tied in line together somewhere.

Yankee's right, may be a vacuum breaker somewhere but not likely in the wall but rather in a cabinet.

Alumaholic · 08-24-2011, 01:40 PM

I've read your thread twice, and I can't understand why you are so concerned about your vent pipes. The capacity of your gray water tank is not effected by your vent pipes.

By the way, you cannot see into your gray water holding tank from your shower. As others have mentioned, there is a P-trap that should have water in it even when the gray water holding tank is empty.

Please describe the malfunction you think you are having so we can help.

Alumaholic · 08-24-2011, 01:45 PM

Are you level? If your Airstream is sloped away from the dump valve, you will never attain the nirvana associated with a thorough dump.

vswingfield · 08-24-2011, 01:50 PM

Quote:

Originally Posted by KerriO

I was probably misinformed (or I mis-read) about being able to look into the shower drain. Regardless, I still think there's more water to be drained. (And I'm bummed that there's not a simple non-monitor way to check that gray water level!).

I guess we'll need to get the ladder out, because I can't see any vent pipes from here. (I assume their location on the roof would be somewhere directly over the tank's location?). There is something with a conical black plastic cover, that is maybe 8" in diameter, and not very tall. Is that the vent pipe? I just have no idea what I'm supposed to be looking for.

Check here for photos of the vent pipe aluminum covers that are on the roof Vent pipe cover-aluminum 101158 [101158] - $42.95 : Out-of-Doors Mart!, More Airstream Parts on-line than anyone!

KerriO · 08-24-2011, 01:51 PM

Yes we are level. My concern is not the capacity; my concern is that it is not draining well, and I believe it didn't drain completely during the dump we did prior to this "five-gallon" drain (which is why we were surprised by how quickly it filled). When I search the forum, everyone who has draining issues gets the response to check for obstructions in the vents.

ETA (x-posted): Thanks vswinfield — that helps. Don't know why I didn't think of looking up the part!

Alumaholic · 08-24-2011, 02:05 PM

... the large diameter of the dump valve itself should allow the holding tanks to "self vent" when you open the dump valves. The vent pipes themselves allow sinks and shower to drain by eliminating vacuum in the drain lines to the holding tank. There may be exceptions, but this is generally how drains and vent pipes and holding tanks work. Any slope away from the dump valve will keep your holding tanks from draining completely. Do you have a torpedo level? Check your level side-to-side.

aftermath · 08-24-2011, 02:18 PM

Are you sure the gray water monitor is working? One way to check is to run water in the sink until you see the water actually backing up in the shower. At this point you will know that your tank is full.

Would it be possible that you are getting a full reading when the gray tank is far from full. You said that it was full but "not that full."

I also have a vent under the sink in my 2006 25 FB that does not exit the trailer. A clogged vent might slow the draining of the tank but I would check to see if the tank was indeed full before I did anything else. There is a way to recalibrate the monitors if this is a problem.

Silver Otter · 08-24-2011, 02:53 PM

It only took us three days of (injudicious) water use to fill the gray tank two weeks ago to the point at which it backed up into the shower. We don't often "camp" without FHU, so didn't control our sink and shower water use properly for a three-day stay. Interestingly, the monitor never showed red even when at high water. It also shows 3/4 full after about a day in camp, but that's not right either. Hmm . . .

Jammer · 08-24-2011, 03:59 PM

The holding tank monitors are rarely accurate and should not be counted upon to provide reliable results for anything as important as troubleshooting. The best you can hope for with them is that they'll show empty when the tank is empty and full when it's overflowing. Anything in between is a guess.

As an experiment you may wish to run the shower until your greywater tank is full as indicated by a slight backup of water into the shower area. Then you can determine whether there is really a problem based on the amount of water in or out.

KerriO · 08-24-2011, 04:18 PM

Thanks all. After a full 1 1/2 months in the trailer we are very aware at this point in regard to how much water use it takes to fill the tank, and we definitely were nowhere near that. We were three days into a nine-night stay, and were aiming to get it through that time: no showers, doing most dishwashing at the washroom station, etc. To my best experience, the monitor is accurate enough that when it's at the flashing red stage, it means the tank is "pretty full" (which it should not have been unless it wasn't fully drained at the last dump). We are level. I know this because we leveled. With a level. We may not have been level at the dump station the first time around, though. And maybe after this five-gallon dump, the monitor sensors are still wet. I don't know. At any rate, I still think it's valuable that we know and understand where the vents are located, and I will be checking them for good measure! Experimenting with filling the tank isn't an option right now, as we're not hooked up to dump, and we're pretty new to hitching/unhitching/backing-in—not worth it until we're hooked up to sewer! But—this campground has a powered "honey wagon" (hate that word), so we hired it to come by tomorrow and suck us dry—so we should be able to start clean from there and see if we run into this issue again. (And it'll also help, hopefully, clean out the last vestiges of our, "We're hooked up to sewer! That means we can keep the black water tank open!" n00b mistake from a couple of weeks ago!)

Alumaholic · 08-24-2011, 04:59 PM

Honey Bucket sounds nicer that Sh@# Sucker, which is what Marines call it.

I'm guessing you didn't drain your gray water tank completely at the dump station.
Few dump stations offer a perfectly level parking ramp.
Most are sloped, and you must approach from the direction that will slope your Airstream toward the dump valve, not away from it.
Don't fret. This happens to all of us.
And there are few things after parking at a spot with no sewer than to find your holding tanks are still almost full.

overlander63 · 08-24-2011, 06:11 PM

I'm on my way somewhere, so I didn't read this whole thread, but I'll try to help the original poster.
You can't see the grey water in the shower, you CAN see the black water by looking into it from the toilet.
The tank monitors are basically useless. I worked on a 2008 that had a grey tank sensor that showed empty, then full after I put 5 gallons of water in it, then back to empty as I continued filling it.
The vents are on the roof, under white covers, usually 2 of them. Unless they are broken, or you can see cracks in the sealant around them, leave them alone. There's nothing to see there, move along.

ROBERT CROSS · 08-24-2011, 06:42 PM

KerriO

The two roof vents on our Classic are for the black tank and fridge, the white plastic is the BT, you can just see the aluminum fridge vent behind it in this pic.

BTW...if it looks like this re-seal it, as you can see they are prone to leak.

Bob

Silver Goose · 08-24-2011, 10:22 PM

Quote:

Originally Posted by KerriO

... There is something with a conical black plastic cover, that is maybe 8" in diameter, and not very tall. Is that the vent pipe? I just have no idea what I'm supposed to be looking for.

The previous post shows the white PVC covers commonly used these days. The 8" black cover you describe is most likely the bath vent van cover.

ROBERT CROSS · 08-25-2011, 06:04 AM

Quote:

Originally Posted by overlander63

The vents are on the roof, under white covers, usually 2 of them. Unless they are broken, or you can see cracks in the sealant around them, leave them alone. There's nothing to see there, move along.

Terry,

I know there must be a grey tank vent and this thread got me curious.

On our Classic there is no separate fixture on the roof. The manual shows the vent pipe but not where it terminates. Could it be that the black & grey are joined at some point and both vent thru the one vent I have on the roof?
Or is the grey vent hidden behind an interior wall?

The manual also shows an anti-syphon vacuum vent, but no location. Be handy to know where it's located in case of failure.

Bob