Holding Tank Vent Odor

[talgutbir]

Hi, all.

We have a bad smell sometimes when we drive on bumpy or windy roads. I have the OEM cheap covers on top on the vent pipes and heard that the Cyclone/Siphon vents do work. My questions are:

1. I have 3 vents on top. Sewer, Shower, and Sink. I can't understand how the toilet would be the source of smell since the valve is closed and covered with water so the vent on the roof will not create a "pull" since a vacuum will be created. Am I right?

2. I guess the smell could come from the shower or sink drains "pulling" odors from the holding tank?

Thanks for any replies.

[kaypsmith]

Pressure inside the coach being less than the outside pressure is usually the largest source of letting those bad smells into the coach, much like a vacuum cleaner, it is in a sucking mode.

Making sure that the inside pressure is higher will lessen the odors. While traveling the wind will tend to suck those odors out of the tanks. Your shower and sinks have p-traps that hold water for keeping the odor out as well as the water and valve in the toilet.

Those Cyclone/Siphon vent caps do help, as while driving they direct the scent towards the back of the coach.

Raising the inside pressure will have a positive effect for you, close all outside sources of air, and recirculate the AC should help.

[talgutbir]

The question is, which vent would be the one to install the cyclone on? my feeling is that the toilet is not the source since it creates vacuum.

[hermanmullins]

talgutbir,

I have had the 360 degree swivel on three coaches. Just to be sure I have them on all vents. They cured the odor problem on our first coach so I put them on the rest.

Good luck,

Herman

[kaypsmith]

Most of us don't have vacuum toilets, as they are in most cases used on high end coaches with two bathrooms. The vacuum toilets only create a vacuum while being flushed, then the wastes go to macerator style pump which pumps to the holding tank. The holding tank still works just like any conventional holding tank.

Hope this is helpful in understanding why the vent still works in the holding tank, it must be there so that the tank can fill and empty correctly.

[talgutbir]

Maybe I didn't explain myself right. I don't have a vacuuflush toilet. I have a regular gravity one. The vacuum I was talking about was the wind creating while driving and sucking air out of the black tank. Since the black tank has NO other vents inside the coach other than the toilet which is closed unless you flush, I can't see how the odor can come into to coach.

[tbutler]

The source of the odor you are experiencing most likely is the grey water tank. You are correct, the toilet seal should prevent any odor from the black tank entering the coach through the toilet. Grey water has a sewer smell when it has been stored for a while.

It is true you would expect the vents on the roof to have a slight vacuum on them when you are driving down the road. The problem is that there is an even stronger vacuum on the rear of the coach. Generally when you are driving down the road the pressure inside the coach is lower than outside. That said, the waste tanks will draw air inside through the roof vents and into the coach.

If this is something that you experience on rough roads it likely means that on a rough road a sink or shower drain is sloshing enough water out of the trap to allow air to move through the trap. Replacing the water in the trap should restore the seal but if this is a constant problem and the trap isn't holding the water, then using the weather-vane type vent covers on the roof should solve your problem. I would install one on each vent. If you want to save money, installing one on the grey water may be enough, either sink or shower assuming they share a common storage tank. If that isn't enough, install on the other grey water vent. The toilet vent should be the least likely to be the problem.

We have had this problem with a washer/dryer drain in the past. If the washer hadn't been run recently and the drain went dry, we would get strong odors inside the coach. I installed a long neck funnel (transmission fill funnel) in the closet above to feed water into that drain pipe. That way I can conveniently pour a glass or two of water into that drain to stop or prevent problems.

[talgutbir]

tbutler,

Thanks for the help. Its what I needed.

The smell is only on rough roads not a constant problem. I never thought about the washer/drier pipe. I guess it doesn't have its own vent. I will start with the gray vent and go from there.

[jones4110]

I would suggest small amount of Pinesol in grey tank.

[manholt]

Hi Jones and welcome to the Forum!

Because I'm not a Chemist, I don't use house hold items in my plumbing system! Our system is made off materials that you don't find in a home.

Galvanic reaction, I know. Chemical, not. Pinesol is a floor cleaner.

Carl

[jhaig99]

There is a seal on the bottom of the toilet at the floor. It can leak vapor and not liquid if a vacuum is pulled in the coach.I added pine power to my black tank and our on the road smell had the pine power odor.

[manholt]

How long have you used Pinesol in your tank?

[gerryh]

Hello, I can relate to all these smells and problems with these nasty smells, none of the "remedies" worked for me... I eventually replaced the vent valves on the vent pipes that are located under the kitchen sink and bathroom sink.. These valves are on top of a black pipe and screw off, I got good USA made replacements in the plumbing department at Home Hardware, The rubber flaps were distorted on the old ones.. I thought I'd won the battle, but the smell came back, tracked it down to a storage cupboard that had the rough plumbing for a washer/dryer in the back behind a panel. The vent valve at this location was missing it's rubber flap completely, after another visit to Home Depot for the third new valve, all smell problems were cured, Hope this helps, Gerry

[tbutler]

tbutler,

Thanks for the help. Its what I needed.

The smell is only on rough roads not a constant problem. I never thought about the washer/drier pipe. I guess it doesn't have its own vent. I will start with the gray vent and go from there.

Here are Tom's ABC's of plumbing in motor homes. I'm not a licensed plumber and not a motor home technician but I've done quite a bit of plumbing and work assisting plumbers and looking over their shoulders while the work. After living in a motor home for ten years I've seen almost all the plumbing in our coach.

The problem isn't that the dryer doesn't have its own vent. In fact our coach has only one vent for all the grey and black water. That vent is designed to let air flow out of the grey or black water tanks as the waste water feeds into the tank. It is simply a pressure relief system for the storage tanks. Several people are mentioning small vents that are located under sinks. When you pull the stopper on a sink full of water the water will fill the drain line and can siphon water out the trap under the sink if a vent doesn't allow some air to enter the pipe below the trap to break the siphon. The under sink vents are used simply to allow water from the sink to flow down the drain without siphoning the trap. If these leak, they can also allow odors from the tank to enter the coach. As mentioned above, they can be replaced. If you have a roof vent for each fixture then you likely don't have the vacuum breakers under each sink. Your manufacturer chose to use the roof vent as the vacuum breaker for that drain. In some cases, if the drain line from the fixture is short enough from the fixture to the tank a siphon may not occur and that drain may not have any vacuum breaker installed.

For sinks, showers and washing machines, the drain will have a S trap or a P trap in many cases. I understand that some have a flapper valve arrangement, our coach does not. The flapper style valve is designed to be a one way valve allowing water to go down but not come back. If that is a problem you have to replace the entire flapper valve.

For the S or P traps, as you travel down the road, the coach rocks and bounces. This moves the water in the S or P trap and will slosh the water out of the trap, a little at a time. Once there is not enough water to fill the bottom of the S or P trap, an opening exists between the grey water tank and the coach. Then you get tank odor. In the case of the unused washing machine trap, you have a third factor as well. The water in any S or P trap evaporates. The evaporation is slow and in most cases negligible. If a drain isn't used frequently, the trap can dry out creating the same problem as sloshing the water from the drain. When you have a trap with little water in it as a result of evaporation and then you slosh it there will be some escape of tank gases into the coach. The solution is to keep the traps filled with water. Pour a little water down the drain if that drain hasn't been used lately and your problem should be solved. This applies to shower and sink drains as well as the washer. If you don't use the shower in your coach, it's drain will go dry and allow tank odor to enter your coach.

I mentioned above that we've had this problem with the washer/dryer in our coach. The W/D is located in the bottom of the closet with a shelf that covers it. There is a removable panel in the rear so you can access hoses and the drain but it is a pain to remove everything from the shelf and get to the panel in the back. Then you are challenged to get the water poured into the drain without spilling it everywhere else. I drilled a small hole in the removable panel and installed a transmission fill funnel (a funnel with an 16 or 18 inch long tube attached) so that the extended tube is in the washer drain tube. The top of the funnel is in the back of the closet. I screwed it to the closet wall to hold it in place. Now if we're traveling and haven't used the W/D recently we simply pour a glass of water into the funnel. If I need to remove the panel in the rear for some reason, I unscrew one screw, remove the funnel and the access panel can be removed.

In the case of plumbing installed for a washer but the washer has been removed or was never installed, that plumbing should have a permanent seal installed. Purchase a cap at a hardware store and either friction fit it on the top of the pipe or glue it to the top of the pipe. The pipe can usually be trimmed to remove the cap if you glue it on. That can be difficult with the close tolerances in motor homes so I would probably just push the cap on tightly, maybe a tap with a hammer and that should be a good enough seal.

For the toilet the valve in the bottom of the toilet bowl seals that vent. There is also the seal at the bottom of the toilet fixture where it joins the plumbing at the floor level. If that seal has deteriorated or if it is not installed properly it can leak odor from the black tank into the coach. We had that problem a few years ago. I got a new seal and went to install it. I found the original seal had been improperly seated when some work was done on the toilet. I reseated the seal properly and the old seal is still holding. I have the new one in case I ever need to replace the old one.

If all your drains are working properly and seals where used are good, tank odor should not be a problem. If you have to add chemical to a tank to control the odor in the coach you have a plumbing problem. I do add chemical to the black tank in order to help break down tissue and to help keep the tank clean. Nothing is going to make the black water tank smell good. Never flush the toilet when the ceiling fan is running!

[hermanmullins]

Tom,

Good information about the "S"/"P" traps. I had never considered the road movement for sloshing the water from the traps. Great catch.

Herman

[manholt]

I just got off Google on a problem with removing stains from toilet. Mine is a Dometic Master Flush and it clearly states to use non abrasive, no alcohol and no petroleum based cleaners! It gives a list off the good and a list off the bad....on the bad list is Pinesol.

I then checked out our complete waste water system including black, found the same info on no petroleum based powders or liquids!

I used cleaning bubbles and it works on everything, not just sink, toilet or shower!

Just thought you would like to know.

[mewhichard]

I have been battling the sewer odor for 5+ years in my class A 2008 Winnebago Voyage. Sometimes it was there and sometimes it wasn't. Several RV mechanic's and several emails to Winnebago yielded ZERO results, Either couldn't duplicate the problem or locate the source. Put new "mission couplers" on the black and gray outlets with some OK results but did not solve the problem. Bought a video display unit with a 3' camera lead on it. Looked and looked inside and outside the tanks and could not see a problem.

I finally solved the problem with a little insistence from the wife. In the hallway between my bathroom and the galley and below my control panel was a wall mounted vent screen to provide air to the mail wiring chase, after removing the screen and moving all the wires inside to one side and low-and-behold way back in the corner was a sewer vent pipe. Grabbed the pipe and it seemed a little lose, put the camera down there and saw the top of the black tank was extremely dirty, twisted the pipe a little and there was the inlet for the vent pipe to rest in and I could see inside the tank. I guess I found the problem. I had to remove a small section of paneling which was very easy to do so I could get good access to the pipe, Put some sealer on it, shoved it back into the 1 1/2 rubber grommet on the top of the tank, secured it with 2 clamps that I attached to the framing of the wall, reinstalled the small piece of paneling and the corner molding (which came off way to easily) You would never know today that I used to drive the Sewer RV. It could get very smelly in there while on the road! Hope this helps someone down the road.

Mark Whichard

411714

[wigginsjsr]

I have been using lemon Pinesol to clean my toilet, and to deodorize my gray tanks for over 5 years with no known damage to the plumbing. It is not anymore caustic than the motorhome specific toilet cleaners. BTW, Pinesol is much more than a floor cleaner.

[jleamont]

Minor problem....odor from the vent under my sink in the back. I have a vent to the left of the P trap that sits higher than the P trap. I remember a post on these but I cannot locate it. I am unsure how the vent is supposed to work, but it is exhausting some grey tank odor, doesn't bother me but DW is complaining.

what is it called and can I get it at a home improvement center?

the orange guys are just down the street.

thanks

[kingfr]

It's called an Air Admittance Valve (AAV). Get a Studor Mini Vent at Home Depot, $22 - 24. If you have multiple sinks with P-traps, you might should replace them all as the RV manufacturers seem to use the cheapest ones that they can find!

[jleamont]

6 minutes ago, kingfr said:

It's called an Air Admittance Valve (AAV). Get a Studor Mini Vent at Home Depot, $22 - 24. If you have multiple sinks with P-traps, you might should replace them all as the RV manufacturers seem to use the cheapest ones that they can find!

Thank you.

And I will replace all three.

[rsbilledwards]

J,  Put some tsp or some strong cleaner in the grey water tank before you take off and slosh it around good to clean t it up and then drain. Likely the stench will go away. I put solar powered fan vents on mine and zero odors. When I pulled the grey tank out of the Panther, there was some really ugly slimy stuff growing in there, now, nothing.

 

Bill Edwards

[hermanmullins]

Bill,

Do we need to explain what that ugly slimy stuff is? 

As you are aware, this is an informational and instructional forum.  :-), and we will be more than happy to explain in a PM.

Sorry I don't have emotions on my phone or there would be a laughing face.

Herman 

[manholt]

I have been using HP 3% now for about 6 months, in January I loaded a bottle into my water line before hooking up to faucet, then I did the same into my fresh water tank, it was a quarter full at the time.  I then opened all my inside faucets for about 5 minutes.  Let sit for 10 minutes and switch off pump, open campground faucet for 5 minutes, drain gray tank, and no odor.  Before leaving campground, I ran fresh tank as above, then filled it up.  Did the faucet water line here and will do F tank again before leaving.  Talk about "Slime", unreal what came thru in January !   2 weeks ago, nothing!   HP 3% is cheap and everybody carries it !

 

Carl

[jleamont]

It has a musty smell. I removed and replaced the vents in both vanities. Home Depot only had 2. 

No water stains on the carpet under the sink and the valve was not seated. Time will tell. DW is happy so that's all that matters, I tried to tell her it was my cologne 

What is HP 3%?