Opinions please!!! Sewage smell problem

[Kittykatdk]

First off please excuse my topic but i am looking to buy an older RV....it drives beautifully and has only 45,000 original miles. It does not have any issues except when driven it smells awful like raw sewage...but only when driven...but bad enough to make one gag. I do not know the current owner but do see him being a bit of the lazy type who had this rig always plugged in to a city electric and city water line and not maintain it. He specified he had it sit hooked up mostly with some trips in between. He is a bigger guy with health issues. He also noted that although he used the bathroom for #1 never for #2 as he was always at a campground or some kind of facility with restrooms as well as electric and water. I dont believe this but maybe. When i test drove it all tanks were empty..it is cold out...at least he winterized it to some extent! The water in the drains keeps tank smells out and i am ok with it needing a VERY VERY thorough cleaning. I am even ready to repair or replace water holding tanks and all valves. With everyones experience out there would you be willing to deal with this stinky problem to have a rig with a good engine and carb? I plan to live in this full time and completely renovate it. Is there a chance for this poor thing or did he gut it? Ive read horror storries about water pressure from campground hookups causing issues and leaky valves....from everybodys honest opinion...i dont have many options at the moment...is this worth the trouble to have a nice running rv or could this be something super scary and completely hidden inside the walls and unlivable in until fixed. I can scrub and clean before but i need to move in it first before replacing parts. I can live without running water till then obviously but not with a horrible stench. Rolling windows down made it 100 times worse. Any advise would be very very welcome. Thank you

[USMCRET]

Sewage smells only when underway are frequently, if not always, the result of low pressure being created somewhere which is drawing the smells into the coach. It could be something as simple as a clogged vent pipe through the roof, or something not quite as simple. By the way, the smell could just as likely be from the gray tank as the black.

If you have the means, I would think about looking into a certified inspector to check things out for you, or even a mobile RV tech.

Best of luck to you. I like your attitude and willingness to get your hands dirty.

[mjeffrey]

Use that low pressure to diagnose without Driving.

Driving is causing negative pressure pulling air into the cabin thru one of the tanks or somewhere.

Clear the smell as best you can. Then seal up the windows and doors. Then, while inside, turn on the ceiling vent and turn it to high. If you have more than one, turn on both. Turn on the stove/ microwave/ kitchen vent. Turn on the dryer of you have one. All sucking air out.

Now stick your head everywhere and under the sinks where the vents and anti siphon valves are. Sniff test all around.


I our case...
We had a rock jam inside our anti siphon/ vacuum breaker for the black flush system. Ours was under the bathroom sink. Wife even put a bag over it to prove and it inflated like a balloon when driving down the road.

Hard to believe that the path of least resistance was in thru the black tank roof vent, thru the black flush spray heads and back thru the jammed valve.

Was an easy fix for us at that point.

Hopefully as simple for you.

[jacwjames]

Drain plumbing in a house typically relies on a series of vents from each drain to allow air to enter as the water rushes down the drain. This vent system is all tied together with ultimately an exhaust out the roof or side of the house. The Pee traps under each sink/shower prevents the sewer gas from coming into the house.

Make sure each of these Pee traps have water in them before driving.

In an RV there are usually only drains and a venting system that relies on air admittance valves under each sink which allows air to enter when the sink is used.

https://www.lowes.com/pd/Keeney-1-1-...e-Vent/1069119

One of these admittance valves could be defective and when you are driving it could allow the sewer gas to come into the coach.

One way to test would be to take a small plastic bag & rubber bands and cover each of these valves and then drive the coach.

[Winemaker2]

Was there water in waste traps and toilet?
You mentioned winterized and wonder if AF was added to traps. If not interior is conbected directly to black & gray tanks.

[mjeffrey]

Sink vent on left. Anti siphon on right.

[Spk64]

We had same problem. I replaced all the AAV valves under the sinks and put cyclone roof vents on the stacks. No more smells going down the road or after in storage for a while.

[gatorcq]

does it have washer/dryer? if yes, maybe the P-trap is empty.

[exrench]

If the unit has a washer/dryer, the trap associated with it needs to have water or antifreeze in it to prevent odours from the gray water tank. As a previous member said,the gray tank is a very foul-smelling place!

[TripleEEE]

OP

Good advice from the members here.

I would pour water down all the drains and drive it again. It is likely any liquids have evaporated if the unit has been sitting for awhile. It's cheap and easy to try at least.

You may not be able to do any more troubleshooting at this point as you haven't purchased it yet. I would go with the obvious first.

Good luck!

[Bob_C]

Open gray tank valve and shove a garden hose up it and flush....

[keymastr]

I would pass. It sounds like maintenance was neglected for a long time and that he had it permanently parked in one place. Open the toilet valve and look in the tank for the mountain of "solids" that get left there when the tanks are left open for a long time.

Sitting is very hard on a vehicle so very low miles for the model year is not always a good thing. Seals dry out, oil and fuel go bad, brake fluid and wheel bearings absorb moisture that is never driven out through heat because it is not used except for 2 weeks a year in some cases.

I would continue to look for a rig with maintenance records that is clean and does not have a story with it that in your own words you do not believe. You might pay a little more up front and a whole lot less later.

[MisterT]

after many, many miles, and campgrounds with full hookups as well as many times boon-docking for days, the mysterious 'smell' is most often the GRAY WATER, not the black. The air, while under movement when traveling, is negative if a vent or window is cracked or open, and the gray water smell is being pulled into and thru the coach.
Your p-traps are the best defense. Make sure that after you dump, you run water back into each sink and the shower drain so that each p-trap is filled with water, probably a cup full for each. This keeps 'air' from being pulled thru while driving, stopping the 'smell'.
Why is it not the BLACK tank smelling? well, if you have a typical rv toilet, one that has a 'foot flush', then the tank is 'sealed' at the toilet when not in use, therefore no 'air' can be pulled thru while driving.... no smell!

but, rarely, some companies will tie in a bath vanity sink with the black tank, giving the option of this 'black tank smell' being more of a real culprit, though most unlikely.

It is NOT a result of a 'faulty' previous owner. There is not such culprit.





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[Kittykatdk]

Thank you everybody for the replies really appreciate it. I am pretty low on options but will opt for a unit that drives good. Will try to check if adding water to every trap makes a difference. Thank you everybody for your awsome helpful replies. And no it does not have washer and dryer so at least a few less spots to check for problems.