No Grey Water Vent Brave

2001 Winnebago Brave 32ft

Hello Friends. Curious  to see if any other members have found that the grey water tank is not vented? My Brave has acted suspicious since purchasing earlier this year. I noticed when I dumped the grey water that halfway through there would be this sudden loud vacuum surge originating from inside the coach. It would continue until the drain pipe became less than full as the tank emptied. I didn't put much thought into it initially but later and after a replacement of one of the grey water inlet rubber grommets, additional symptoms surfaced. All three of the  drains began to slow and eventually stop completely. This would hiappen with the grey tank full, empty or anywhere in between. Suspecting a blocked grey tank vent, I took a shower one evening, let the water build up in the tub then removed the trap under the bathroom vanity and watched the water in the tub drain without any restrictions. I began to dig into it and guess what? No vent was ever installed at the factory 18 years ago. I  didn't
believe it at first but it has been confirmed. No vent ever installed and only one vent pipe up on the roof which services the black water.  Has anyone experienced this?

Henry

There aren't even air admittance valves under the cabinets near the sinks? That's usually how gray is vented. Maybe they are there and have failed.
Picture is of one inside the cabinet near the bathroom sink in our trailer.

While it's conceivable that somebody screwed up and left the vent out, it isn't by design.  Both the plumbing code and RVIA standards require it.  However, the gray and black vents may be combined (Y'ed together) and I've seen a overly full black tank block the vent path.  I suspect yours was supposed to be one of the Y-types, but maybe an assembly line worker got behind and simply skipped that step rather than signalling to stop the assembly line. That's a really serious thing and few workers have the intestinal fortitude to risk the bosses ire.
What often happens with no vent is that the draining tank sucks the water from the sink & shower P-traps and sucks air in that way.  Then you get sewer odors in the sinks until you ruin some water down the drain again.  Air-admittance valves are supposed to prevent that, but may not have been required in 2001 (they are now).

A "second whoosh" while dumping phenomena seems fairly common, even with a vent in place.  Grat dump flow slows to a trickle, followed by a sudden whoosh and the flow rate goes back up again.  I've noticed it most in Fleetwood brands so maybe something in their plumbing practices?  Not sure just why it occurs except in rigs that have two gray tanks daisy chained together.

Air admittance valves are a cute, legal way  to vent sinks and tubs without vent pipes. As said and pictured, they are usually located under the sink.  They certainly can go bad, but they are easy to change, often without tools.  It is hand tightened on a pipe thread.  Replacements are inexpensive and available at most big box, hardware or plumbing stores.

This does NOT apply to venting the gray tank.

grashley said:

Air admittance valves are a cute, legal way  to vent sinks and tubs without vent pipes. As said and pictured, they are usually located under the sink.  They certainly can go bad, but they are easy to change, often without tools.  It is hand tightened on a pipe thread.  Replacements are inexpensive and available at most big box, hardware or plumbing stores.

This does NOT apply to venting the gray tank.

Click to expand...

I only mentioned it since OP mentioned the sinks started draining slowly.

Understood.  By his description, I suspect he has them.  I wanted to add a bit more description and assure him they are easy to find, buy and swap out.

Great pic!

Busy last couple of days. Sorry for the late  reply and thanks to everyone.

I will look for those air admittance valves in the morning. I have not noticed any plumbing components that were out of the ordinary but I will look closely in the morning and report back. I currently have full hook ups and with the grey dump valve left open, the problem is squelched.

Thanks again

If the factory forgot the tank vent (or it has clogged or broken somehow), an air-admittance valve isn't difficult to add under a sink.  It's basically just a riser pipe Teed into the drain line (after the p-trap) with a the flapper-type valve on top.

Got under the sinks and tub this morning. The bath and kitchen sinks both have Deltatech add a vents. The tub appears to be serviced by the bath sink add  a vent being on the same drain line. Both these vents are mounted as high as possible inside the cabinets.

These vents dont indicate a flow direction. I assume that these vents allow an intake of air? I assume this because I wouldn't be friendly to a vent or vents releasing air from a waste water tank into the cabin. If this is true, I wouldnt expect these to solve the problem I am experiencing.

Another plumbing issue I found this morning is that the tube drain has no trap. There appears to be no room for one unless the drain is routed through the floor into the storage cabinet below. It looks like they ran the drain line in a up hill pitch so as to hold water and act as a trap. The line runs the length of the tub and Ts into the line that services the bath sink.

One other condition I noticed was that the add a vent under the bath vanity was very loose and a few turns from falling out. The kitchen vent was tight leading me to wonder if the previous owner found themselves standing in a tub of shower water and tried to figure it out.

I will spend some more time on this today. I want to make sure I have given correct  information to the forum. I  will open up the bath access from the dinette side to get a better look at the tube and vanity plumbing. That tub drain looks like a hack job from the access panel in the bathroom but I will confirm with a better look later today. My current feeling is that this is alot of work to skip venting the grey tank to the roof and I suspect all that was done, doesn't solve the problem I am having and If these add a vents vent waste water fumes into the cabin, they will be gone very soon.

Could it be that the add a vents were installed to prevent the traps from losing all their water during a dump? That just might be what they did and would be neccessary if they connected a grey tank vent to the black water vent. Maybe that hacked tub drain gave them some pause about tying those two vents together as it seems that the pitched tube drain would only hold water under certain circumstances.

Thanks to all

Henry

The air admittance valves ("add a vents") allow air to flow into the drain to prevent a suction from pulling the water out of the trap and also block tank odors from escaping into the cabin. If you have a slow draining bathroom sink and the trap is clean, try just removing the vent temporarily to see if the sink then drains properly. If it does, that's a sure indicator the valve is faulty and should be replaced.

The tub may have a mechanical HEPVO trap installed that looks more like a long pipe fitting than a 'P' trap.

https://www.amazon.com/HEPVO-BV1BUB112-1-1-2-TRAP/dp/B00NLMPLDU

Henry,
Look under your tub for a HEPVO  trap. Google it to see what it looks like. HEPVO traps can be installed horizontally,  therefore requiring less space between the bottom of the tub and the floor.
Concerning the vents.  I've had 2 Winnebago motorhomes . Both had only a single vent on the roof which served both tanks via a sanitary Wye in the wall. Both of those coaches also exhibited the secondary whoosh when dumping.

It's true that the air admittance valves aren't the same a s a vent - they only let air in. not out. They function while dumping the gray tank by letting the tank "suck air" as the water level drops. Doesn't help displace air as water flows into the tank, though. That's one of the two functions of a tank vent (the other is air intake, just like the admittance valves).

Have you looked at the plumbing diagrams for your coach to see where the tank vent is supposed to be? They are available on the Winnebago site.  May be possible to verify whether it is missing altogether or simply not functioning well.

Thanks for all of the help. I was not able to tear into things today and will be heading north tonight. I wont be back to the coach until Monday. I will continue the process then. I do have the plans from winnebago Gary. I have both a hard copy and an electronic file which will be with me on my trip north.

Have a good week and weekend all. I will follow this through next week and again, thanks to all the replies. There is something to learn from all of them.

Henry

Digging into this and have some new info and revised info

First, my original assessment of tbere being no vent on the grey tank and no trap on the tub are incorrect. My apologies.

Second, the grey tank vent is connected to the black tank vent via a standard Y fitting. Again my apologies.

The plumbing layout looks to be as detailed in the plans I have for this winnebago.

The plumbing system is clear of any solid material that would cause an obstruction.

The problem appears to be a poor choice of design for venting the grey tank. Instead of direct venting the grey water tank, it was instead vented from the drain line of the tub. This chosen drain line isnt pitched properly and even when the coach is level, water will not drain to the tank but instead, the water sits in the drain line blocking the path to the vent. The coach currently is off level slightly to the side that would assist the water to drain out of the pipe. Even with this slight angle, the vent is still blocked causing water to cease flowing into the tank as the pressure  builds because the air cannot escape. This condition only occurs when the grey tank dump valve is closed.

I dont think I can easily change the pitch in the line however I am still considering this. Ultimately and surely the best way would be to direct vent the tank witch disassociates the vent from piping that directs the flow of waste water. This is done on the black water tank.

And the Add a Vents? I am pretty sure that since the grey and black tanks are sharing the same vent without any back flow prevention, these add a vents are installed to prevent the water in associated traps from being sucked out during a grey tank dump and reducing the possibility of black tank gasses backing up into the cabin. I believe these add a vents are of a safety design and wouldn't be activated if the grey tank vent was performing its function properly.

Not sure yet how to resolve the problem.

Thats all for now

Thanks to all and I will update as I figure things out.

Henry

Thanks for the update.  That explains a LOT!

All drains from sink, toilet, tub, washing machine, etc in a house have vent lines to allow air into the pipes and allow water to flow smoothly.  It also prevents traps being sucked dry.  The Add a Vent does the same thing without need of the vent pipe.  Since all drains are working, they must also be working.

The drainage system in the coach is a little different than the drainage system in a house primarily because waste water is draining into a sealed tank that needs to be given the full time ability of taking in air or sending air out. This is the function of the tank vent. In this case, the vent was adapted into the service line of the tub drain which is approximately 6 feet of service line from the entrance of the tank. Because the tub drain originates very close to the floor, there isnt enough hieght to maintain a proper pitch to the tank entrance. Prooer pitch is required to prevent waste water from sitting in the tub service line.  I must find a way to either re route the tub service line for a better pitch or install another vent pipe line that avoids being blocked by the poorly pitched tub line. The tub service line would work fine if the tank was vented properly, even with the bad pitch. Water would still sit in the pipe but would still flow to the tank without stopping and without puddling up in the tub.

The add a vents shouldnt be a part of the main function of the drainage system. Air isn't required to enter or exit any drain line through the add a vent. In fact, if the tank was vented properly,  the add a vents could be removed without compromising the functionality of the drainage system. The only time these add a vents would open would be during a very high volume of water flow from the tank. This flow would need to be so large that it exceeds the air intake ability of the tank vent. Its because of this that I believe they may never be needed but I won't know for sure until I vent the tank properly and dump a full tank. I could then better evaluate the use of those add a vents which I believe to be only there as a vacuum safety valve in case the tank vent is either blocked or its value is exceeded. The jury is still out on this but I am quite certain that the add a vents were not designed to operate under normal water drainage use.

I am considering installing a secondary vent line which will run Parallel but above the tub drain line from the vent to a point very close to the tank inlet. This won't be as good as a dedicated direct vent but should be good enough to allow a constant flow of air in and out of the tank.

If there had been a dedicated direct vent installed at the factory, I believe none of the problems I have experienced would have taken place. In order to do this, there must be an additional hole in the top of the tank that is used solely for venting. This was done on the black water tank. For some reason it wasn't done on the grey water tank and I believe this to have been a very poor decision but may have been too difficult given the tank design and the ability to get the pipe to the roof. There isn't a good enough excuse though. This is because the design chosen dosent work.

Updates coming

Thanks to all

Henry

Have you asked Winnebago about this?  They may have a suggestion, especially if this problem was corrected in later production.

No Lou, I have not but may have time to spend on that this Friday. It would be intetesting to see what info I get and if there has been any previous complaints on record.

My current plan is to cut the vent from the tube service line, cap the pipe on the tub side and route the vent pipe just above the tube drain line to the tank inlet. Cut the pipe there, add a tee and connect the new piping from the vent there. That will solve the problem for sure. The tub drain will be fine. I always blast out my drains with the niblet blaster when emptying the crap tank. As long as the water line remains below the interior of the tub, all is good. I think there might be a slight adjustment available on the tub line too. It wouldnt be much but better than nothing. I will take photos and post so that members can better see the problem and my remedy.

I will pick up the parts this weekend and if all goes as planned, do the mod on Monday and post pictures.

Thanks to all

Henry

Would like some thoughts.....

I decided a few days ago to re-route the vent line from the grey tank to vent. The current vent piping is shared by the tub line which has inadequate pitch resulting in standing water in the pipe which blocks the path of air to and from the vent. My modification will eliminate the blockage and create a full time unibstructed path from the tank to the vent. The grey tank vent pipe and the black tank vent pipe are adjoined 3 ft below the roof and use the single vent pipe that is on the roof. There is no known back flow device to prevent tank gases from one tank flowing to another. I personally dont like that design but after thinking it over, maybe bad results from this design might not be of great concern. I plan to get the parts to modify the grey tank this weekend and make the repair on Monday. One other option I have is to get the parts for a second roof vent which would allow  me to dedicate each vent to a tank. It would require some additional work but doesn't require any change in piping. I would only need to extend the grey tank vent line up to the roof from its current location.

Is it over kill to do this or is it something that should be done or maybe something that should have been done in the factory?

Thanks for your input in advance

Henry

The only issue I can think of is if you lose the water in a P-trap.  With separate tank vents you'll only get greywater odors inside the rig.  Combining the tanks into a single vent can let black water fumes get sucked inside.