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Bad Odor Coming From My RV's Bathroom Sink Cabinet

by Ann
(Lenhartsville, PA)

This Could Be Causing the Bad Smell In Your RV

This Could Be Causing the Bad Smell In Your RV

I have an odor in my bathroom sink in my 5th Wheel. When you open the cabinet under the sink, the smell is terrible. I don't know what could be causing it.

The 5th Wheel is always parked in the same spot. I can't figure out why only under the sink in the bathroom would be this smell.

ANSWER: Hi Ann, there could be a couple of things that are causing your odorous problem under your RV's Bathroom sink.

My first and best guess is that you have a bad Air Admittance Valve (pictured at the top of this page). Some RV manufacturers use Air Admittance Valves under sinks in place of having a roof vent for the sink.

When you drain water out of your RV's sink, the draining water creates suction (vacuum effect) on the valve, which then opens and allows air into the pipe, which in turn allows the water to drain freely into the holding tank. When the water is done draining, the valve is supposed to close tightly and seal out any sewer smell or, in your case, gray water tank smell from coming in the RV.

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Based on your description it sounds like your valve is not sealing properly and may need to be replaced. Replacing this valve is fairly simple in that in most cases the valve just screws onto the pipe. All you will need is a big pair of slip joint pliers to help unscrew your existing vent. To install it all you do is put some Teflon Plumbing Tape on the threads of the new valve and tightly screw it on.

Take a look at the video below to see how easy it is to replace an Air Admittance Valve:

Here are the items mentioned in the video:

360 Siphon Roof Vent Cap

Studor Redi Vent

The odor you are smelling from the gray water tank is usually from decaying food particles in the gray water itself. You might want to also start using some Enzyme Holding Tank Treatment in both your grey and black water tanks. The enzymes in these treatments digest waste and work quite well to minimize holding tank odors as well as being environmentally friendly.

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Another cause could be that if you do have a roof vent on the top of the roof for your RV's bathroom sink, the vent pipe leading up to the roof has a crack in it, allowing fumes from the holding tank to escape under the sink, or the roof vent is blocked by a birds nest, wasp nest, etc. and is not allowing the fumes to escape. You could have had a little varmint like a mouse or rat that has crawled under your bathroom sink cabinet and died.

Lastly, if none of the above solves the smell problem in your RV, you might want to check your RV's house batteries as they could be the source of the foul smell in your RV. If the house batteries are overcharging or low on fluid, they can produce a foul-smelling gas that can be mistaken for a sewer smell.

I hope this information helps.

RVing Al

Comments for Bad Odor Coming From My RV's Bathroom Sink Cabinet

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Solitude smelly water
by: Tim

We own a 2017 Grand Design Solitude fifth wheel. We have had a bad smell coming from the plumbing mostly in the bathroom but sometimes in the kitchen.
We have tried every solution suggested to no avail including changing the hepvo valve back to a p-trap, but it did not help. After much analyzing we came to the conclusion that the smell was actually coming from the fresh water coming into the camper and it is worst when we are hooked up to a municipal(city) water system. We do not notice the smell when we are hooked up to a private water system.
I believe it must be a reaction between the city water and either the hot water tank or the supply pipes going to the faucets. The problem has always been worse in the bathroom but noticeable in the kitchen. Any thoughts would be much appreciated.

Foul odour
by: Anonymous

First thought was rv fridge had an ammonia leak, but fridge was working perfectly, then thought smell was coming from grey or black tank. Thorough cleaning and smell still persisted. Many searches on google and finally the light bulb came on and checked the battery which was warm to the touch and solved the mystery source of odour. Thank you for the remedy to what could have been an unnecessary expensive fridge repair

Air admittance valve
by: Ron

The problem with AAV’s (air admittance valves) is the spring gets weak or fails completely. To permanently solve that problem I found was to install the Hepvo valve. As an added bonus it also eliminates the "P" trap therefore giving you a little more room under the sink.

Response to help asap to smell
by: Clark

Found out the source to the fish smell. No it wasn't battery compartments, wasn't vents , wasn't grey tank or black tank. It was the toilet seal. So needles to after ripping the toilet out .the smell was instantly gone. So today we are on our way to buy a new toilet.

Help please asap
by: clark

I have done all recommended steps to clean grey and black tanks. And I have a fishy smell coming from my bathroom still after a week and a half I've checked my vents. I've flushed my black tank and treated both grey and black I've even driven it around as recommended . To give it a good swish .now what do you recommend. Please help.i. almost ready to rip out the toilet and put in new toilet and flooring.

Bad Odor
by: Anonymous

Well, after five days of searching I found my odor, which btw was horrible, was coming from my battery compartment. When I removed the battery it was very warm and likely near becoming a disastrous situation.

Fishy Smell
by: Geri F

We started getting a port a potty almost fishy smell in our rv on the 2nd day of this trip. We used 3 weeks ago and had no issue (flushed tanks after that trip) but now this started. We opened the wall behind the bowl no odor. If you stick your nose in the toilet bowl the smell is not coming from there. We can't pinpoint the exact source ie: under sink from toilet etc. We have flushed our black tank several times but the odor remains and is permeating thru out. We think it is coming from the bathroom. Only thing we did different this trip is use the heat and water pump about a day prior to the smell beginning. Any insight?

Thank you

Sink smell
by: Anonymous

I have found that the pipes themselves will get sludgy and need a good cleaning.

by: Kim

Hello we have a 44 foot camper that we live in and it is hooked up to city water and a septic tank in the last few weeks we have noticed a very bad smell coming from the drain of the shower what can we do to fix the smell .

Smell under sinks
by: Dave

I found my RV smell to be coming from a small leak in my kitchen tank. The over flowing used water was laying trapped on the protective cover under the RV. I discovered the leak when I lowered the protective cover to look for something else and the stinky sludge spilled out. I fixed the leak, cleaned then reinstalled the protective cover. Smell is GONE!!

Smell under the Sink
by: Brian

Install on of these, as I have, and you will eliminate the smell.

HepvO waterless RV Sink Trap

sewer smell
by: Anonymous

I have sewer smell coming out of the drains in my tub and in the bath. I have a separate tank for he kitchen sink.
I looked at the roof vents they look clear, I also took off the pee traps also clean I took off the vent under the sink and the valve also seems to be ok
the odor only comes up when you turn on the water
hope you can help

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