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friedablue · 09-08-2015, 06:43 PM

We're on an extended trip in southern Utah, and it is the first time we've used our Fantastic fans for cooling. (usually it's cool enough where we are or we need the a/c). Now, when we have them running we are getting a mild odor towards the middle of the trailer( 25' Flying Cloud) that is reminiscent of methane gas. No odor when using the A/C, or when fans are off. It doesn't appear to be coming from the bathroom or any drains or the dump area( we usually only hook that up when we need to dump). Anyone have any advice? I've heard about having back pressure in the vent/tank. Could it be this and the odor stays low until the fans pull it up?

CRH · 09-08-2015, 06:48 PM

It may be coming from the black tank via the toilet flange gasket. A strong exhaust fan can pull up offending odor . Try shutting the bathroom door and see if it goes away.

daveswenson · 09-08-2015, 07:13 PM

It doesn't work well to run FF's without a source of air coming into the trailer. I usually keep both my vents open but only run one fan. If I want more air I'll run both fans but open windows. If you run the fans without a source of fresh air it's going to get it somewhere. If you flush a toilet you get stink.

richinny · 09-08-2015, 07:18 PM

an overcharged battery can give off a similar odor. see if the batteries feel warm. you can also turn off the propane at the tanks and see if you still get the smell.

Belegedhel · 09-08-2015, 08:21 PM

This might be a stupid question, but are you sucking air out of the cabin and blowing it out the roof, or pulling air in from outside and pushing it into the cabin?

If pulling from outside, you might be getting fumes from the plumbing vents.

If sucking from the cabin, as mentioned above, you have to get the air from somewhere. You may have a dry trap in one of the sinks/shower, which is allowing air to come into the cabin via the plumbing vent stacks, through the grey/black tank systems, and up through the dry trap and the sink or shower drain. So try running a quart of water down each of the drains and then try the fans and see if that makes any difference.

good luck!

friedablue · 09-08-2015, 08:42 PM

We always have at least one window open when running any fans, so thei air is being sucked in from outside. This has now happened at two different locations. We always flush the sewer between trips and have done this between locations. We've filled sinks and unplugged them to send a rush of water through the traps, we have the bathroom and shower doors closed( although there's a considerable gap under the bathroom door) the smell doesn't seem to be coming from either place. We've turned off the gas and it doesn't smell at all like propane anyhow. Batteries look fine. We've had a few other issues with this trailer-mostly because of installation issues(factory), maybe it was a Monday or Friday build and someone forgot to seal the stack? I don't know how that attaches to the tank...but could that allow the fans to suck odor up and out the wall it runs up? BTW plumbing is my nemesis.

CBWELL · 09-08-2015, 08:58 PM

Try opening different windows. We run the fantastic in the centre of the trailer, and have a window open on both ends. Haveing more window open to supply air,than fan can eject prevents a negative pressure in the trailer. If you have a negative pressureit, it can potentially have sewer gas enter. Also check to see if someone put a "cheater" vent under the kitchen sink. Chris

fwjumper · 09-09-2015, 11:30 AM

Hi Friedablue,

Is there water standing in your toilet after you flush or does it all drain out after a few minutes? If it is dry, that is likely your problem. If not, check to make sure that the fan that is open, but not running isn't near the vent stack on the roof. I do hope you find the issue soon. Much luck to you.

Wayward · 09-09-2015, 11:53 AM

We've had this happen twice.

One situation, before we knew better, we were pulling black tank gas that exits from the roof vent. Once it was coming in via the bathroom ceiling vent we'd forgotten to shut. The other time through the front skylight which was open. Kinda random. Seems to depend on the weather or which way the wind was blowing.

Second time was very hard to find. Turned out that the foam toilet flange gasket had flattened out like a pancake and the Fantastic fan was pulling sewer gas in from there.

Gene · 09-09-2015, 01:14 PM

If you have a Fantastic Fan close to the black tank soil stack (vent), make sure it is exhausting air from the trailer. The FF's have many versions and some have a reverse button. A fan close to a vent should be on exhaust. Or one may have been wired backwards and sucking air from near a vent. To fix that, just reverse the wires to the motor.

Of course, you may be picking up odors from another RV, or from a vent in the CG. I've seen PVC about 8 or 9 feet up between sites in a few CG's that vented the CG sewer system. Some times the wind would blow it toward us.

Gene

Shiloh4570 · 09-09-2015, 01:15 PM

My money would be on the Anti-Siphon Trap Vent Device (ASTVD) that is under your kitchen sink, your bathroom sink, and somewhere connected to your shower vent. I experienced a similar problem a few months ago. Pulled the ASTVD off, took it apart, lubed the little rubber diaphram with some Aerospace Protectant 303, re-installed and the problem went away.

tomterrific · 09-09-2015, 01:34 PM

We recently experienced a similar odor and it turned out to be overcharged batteries. As noted above, check to see if the batteries are warm/hot to the touch. If so, you are overcharging them. We only had this problem when we were plugged in to shore power in a location that did not require use of the AC.

Farmer Dan · 09-09-2015, 01:37 PM

We have had the same experiences that Wayward describes. It happens several times a season with our '02 Classic.

Dan

HowieE · 09-09-2015, 01:46 PM

Quote:

Originally Posted by Shiloh4570

My money would be on the Anti-Siphon Trap Vent Device (ASTVD) that is under your kitchen sink, your bathroom sink, and somewhere connected to your shower vent. I experienced a similar problem a few months ago. Pulled the ASTVD off, took it apart, lubed the little rubber diaphram with some Aerospace Protectant 303, re-installed and the problem went away.

A very interesting and sensible idea. If the fans are short of air they will pull it from somewhere and a dry vent line to the gray tank would serve that need.

Open more windows.

Iys.Da.Bye · 09-09-2015, 02:11 PM

Roof vent is my guess as well as right next to bathroom fan. Our 1990 29' Excella had a bad smell in the bathroom. Thought vent pipe was apart so removed metal cover and cabinet. All O.K. They had a massive hole cut in floor for the pipe. I filled it with foam and smell disappeared. Never noticed any leaks so may be where vent enters tank. Harvey

The Ice Man · 09-09-2015, 02:35 PM

Some of the solutions seem dramatic. Have you checked the AAV (air admittance valve) under the sink? It's a $5.00 part. If it's stuck you will suck grey water tank air into your trailer when you run the fan. AS part number 60538,Vent, V200 Automatic. Available at any plumbing supply store and many Ace or big box hardware stores.