Sewer gas smell in bathroom

[The Force]

We have 2021 Dynamax Force and our bathroom smells like sewer gas from time to time. It smells like that with the fan on or off. Thoughts?

[RickV]

Look under your sink there is probably a Air Admittance Valve there that has malfunctioned. Easy to replace. I have found over the years it is better to spend the extra $$$ and get a better replacement valve they are available at Lowes, HD

[FFred]

Look at your toilet bowl. Some have a hole 3/4 of theway up in the back of the bowl.

It is there so if the flush valve fails to stop all the water , the bowl will fill and the excess water drains into the black tank.

These system depends on some water entering the overflow hole to form an air block to the tank gas , similar to an under sink U .

Might be worth the experiment to fill the bowl to see if it still smells after some water goes down the overflow drain.,if your toilet bowl is built like this.

[NJKris]

I discovered that in temps 85 or hotter, if tank is not dumped every few days, and I don't double the amount of tank treatment (I use TST orange syrup), horrible things can happen with fumes, causing you to run outside while trying not to wretch. You being in NOLA, this would not surprise me. Black tank down there can turn into a horrid crock pot right quick!

[bclemens]

Originally Posted by The Force

We have 2021 Dynamax Force and our bathroom smells like sewer gas from time to time. It smells like that with the fan on or off. Thoughts?

What are you using for tank treatment? (google "geo method")

I also make sure I let go of the toilet flush pretty quickly...it almost needs to "snap shut". Cover those two things and if it continues we can look at other items.

[TitanMike]

Originally Posted by NJKris

I discovered that in temps 85 or hotter, if tank is not dumped every few days, and I don't double the amount of tank treatment (I use TST orange syrup), horrible things can happen with fumes, causing you to run outside while trying not to wretch. You being in NOLA, this would not surprise me. Black tank down there can turn into a horrid crock pot right quick!

Over the years I've read on almost all toilet chemical instructions words to the effect "in hot weather more frequent addition of chemucal may be required to control odor".

Vents carry odor up and out but when flushing the longer the flush valve is open "at the close of busuness" there will always be some odor escape. It's the strength of that small amount that does the damage and more deodorizer in the tank is needed in hot weather.

[KRedburn]

When using your fan in the bathroom only have it on at 10 - 20% speed if you can adjust.
Any higher and a small vacuum will be created. When you press the toilet ball valve you will get some odor.

Use the geo method (google it) minimal if any odor.
Dump black tank only above 3/4 full or if you must put water in to get it to 3/4 min and then dump.

don't know on a force unit but on my 2018 DX3 the lav sink is connected to the black tank. (easy to fill black tank up before dumping)

[SacRV]

Originally Posted by RickV

Look under your sink there is probably a Air Admittance Valve there that has malfunctioned. Easy to replace. I have found over the years it is better to spend the extra $$$ and get a better replacement valve they are available at Lowes, HD

I've seen this mentioned many times before. My question is how does that affect the black tank? My trailer has two grey tanks with the bathroom sink going to one of them. So it would appear any gases coming from this valve would be from the grey tank and not the black tank.

Just trying to figure that out.

[jeff64]

Whether you have 1 o 2 gray tanks there will be an air admittance valve incorporated. The tank residue can start to reek ,poop or not. Have heard that on some the gray may feed into the black, but haven't had that experience personally. I have had a leaking AAV on my galley tank. It smelled pretty badly

[jmezz911]

I second the use of the Geo Bio Method.

https://www.trbowlin.com/bio-geo-method/

[Jim in Halifax]

Some bath room sinks do not have a proper "p" trap system....Just that new in line round piece of crap

[Barry Allen]

I just had this exact scenario. After a long frustrating time trying to diagnose, in the end it was the plastic toilet. Must have gotten "stuff" leached into the cavities somewhere. On faith, I decided to upgrade from the 301 (factory-installed plastic) to a 310 (ceramic). Totally that was the source. In fact, I put the old toilet in the garage waiting for trash day and my wife said "get that thing out of here, it stinks!". It did. Quite unbelievable actually. I could find no defects.


The unplanned benefit is the new toilet is heaven. No more squeeks, feels just like it should not like a cheap RV nasty piece that you worry is going to blow apart when you sit on it. In retrospect, I should have done this upgrade long ago anyways.

[Johnny Boy]

2021 rig and you have to replace parts already. Why don’t the manufacturers get it correct the first time. It’s so sad how these Rv’s are cranked out for big money only to have the owner “make right” what should have been right in the first place. It’s upsetting.

[bclemens]

Originally Posted by Johnny Boy

2021 rig and you have to replace parts already. Why don’t the manufacturers get it correct the first time. It’s so sad how these Rv’s are cranked out for big money only to have the owner “make right” what should have been right in the first place. It’s upsetting.

??? Oh boy, love these posts . You don't even know what is wrong?!?!? Someone "else" said "Oh it's probably the air admittance valve". We still haven't verified that.

Smells like sewer from "time to time". Most RV bathrooms smell like sewer every time you open the valve, if you leave it open for too long.

The OP still hasn't even confirmed what they are using for treatment, if anything.

[MoJoe1003]

Originally Posted by Johnny Boy

2021 rig and you have to replace parts already. Why don’t the manufacturers get it correct the first time. It’s so sad how these Rv’s are cranked out for big money only to have the owner “make right” what should have been right in the first place. It’s upsetting.

Apparently you didn’t do any research before posting. Dynamax installs Porcelain toilets in the Force, DX3, DYNAQUEST and Isata 5 models.

There is nothing in OP’s posts, at this point, that would indicate replacement is the answer.

[CedarCreekWoody]

I also recommend checking the air admittance valve. This is a common problem with the exact symptoms you describe.

[Larry-NC]

Originally Posted by Barry Allen

I just had this exact scenario. After a long frustrating time trying to diagnose, in the end it was the plastic toilet. Must have gotten "stuff" leached into the cavities somewhere. On faith, I decided to upgrade from the 301 (factory-installed plastic) to a 310 (ceramic). Totally that was the source. In fact, I put the old toilet in the garage waiting for trash day and my wife said "get that thing out of here, it stinks!". It did. Quite unbelievable actually. I could find no defects.

The unplanned benefit is the new toilet is heaven. No more squeeks, feels just like it should not like a cheap RV nasty piece that you worry is going to blow apart when you sit on it. In retrospect, I should have done this upgrade long ago anyways.

The Dometic 300 (not 301) plastic toilet is not used in Dynamax motorhomes which is the topic here.

The 300's two-part design allowed urine to seep into a cavity between the two layers at the bottom. For a while Dometic was providing free replacements. Now they will give a $75 credit towards an exact-fit, ceramic replacement 310 unit.

[mnoland30]

It is always a good idea to check your vent pipe. Just use a hose to run a little water. If it is clogged, you'll have odors. Our houseboat had a failed (by design) vent, and the only way we could control odors was with Oxyclean. Of course that ate the aluminum tank, so it had to be replaced. We use Walmart TST now (with a working vent) and have no odors.

In our trailer, we use the Geo method, again with no odor. Our old trailer has a P trap, so we don't get gray tank odors either.

[milkman55]

I use the Geo Method and Happy Vamper as the digestive additive along with Calgon and Dawn liquid. Our issues have dramatically decreased since we started this combo. Regardless, every time the toilet valve is opened, it’s a direct line to the black tank. Always leave water in the bowl and close your toilet lid. Also don’t run the vent fan when the flush valve is open as it pulls odors from the tank.

[The Force]

Thanks for the information and comments. I am calling the Manufacturer Rep, was just seeing if anyone had a simple fix.

1) So there is no Admit Valve under the bath sink? Should there be one?

2) I use Porta Pak tank deodorizer. Is there a better treatment?

3) Has a ceramic toilet, not plastic