Smell from holding tanks

[mel s]

Originally Posted by WeatherTodd

Hmmmm Mel... no familiar with indoor plumbing? Why do toilets have vent stacks?

When a residential toilet is flushed, (or a sink is drained), air MUST be drawn in somewhere.
That is why all drains are plumbed into a vent stack.

A residential toilet siphons the bowl content into the sewer pipes.
If there was no vent stack, flushing a toilet would suck air in through one of the P-traps, removing the necessary water from the trap, thereby allowing sewer gas into the house.

Most RV toilets do not actually "flush".
They simply drop the bowl content into the black tank when a big hole into the black tank is opened with the "flush" pedal/lever.
When a RV toilet is "dumped" into the tank an equal volume of air is, (aka: MUST be), expelled somewhere.
Often, if/when conditions are right, (wrong?), that air is expelled from the black tank into the bathroom via the same open hole that the bowl content drops through.

Mel
'96 Safari

[bukzin]

Originally Posted by mel stuplich

Ray,IN
A "vacuum breaker" is a device like these: safety.cat.com/cda/files/572649/7/3126B
"Vacuum breakers" are used in fresh water systems to prevent the contamination of the water supply.

You must mean "air admittance valve" or "mechanical plumbing vent" like these: https://www.google.com/webhp?hl=en&t...+vent&tbm=shop
They are used if/when/where real "through the roof" tank vents are difficult to incorporate/plumb into sink and/or tub/shower drain systems...(and, IMO, many times to simply save a buck).

Mel
'96 Safari

These can be super handy in some set-ups; they do save mfg and installers money.

For standard homes some building codes ban them.

[Ray,IN]

All holding tanks (each one) must have a roof vent as required by RVIA regulations. I don't have the link handy, but it is in another similar post I replied to last week.
Do have it too:The Recreation Vehicle Industry Association: Standards Look under Plumbing Standards-4th bullet.
BTW, thanks Mel for correcting my errors.

[mel s]

Originally Posted by Ray,IN

All holding tanks (each one) must have a roof vent as required by RVIA regulations. I don't have the link handy, but it is in another similar post I replied to last week.
Do have it too:The Recreation Vehicle Industry Association: Standards Look under Plumbing Standards-4th bullet.
BTW, thanks Mel for correcting my errors.

>
Ray
Your only "error" was simply an often made "terminology mix-up".
Mel

[broadrun]

After reading through this thread, it seems like the consensus (just barley though) is to make sure you use lots of water and some dish washing detergent when half full.

Doesn't anyone use any RV Holding Tank Treatment? I would assume that the stuff they put in Don's John's would be ok. The reason I ask is because the treatments I recently purchased haven't seemed to work very well. They are the little bags that have powder which dissolve and the claim is that one baggy treats 40 gallons. It occurred to me to then smell the treatment bags and they smell awful - almost worse then the waste.

[Cat320]

Originally Posted by IndianaJoe

I had a similar problem with holding tank odors. I installed a "Cyclone" holding tank roof vent and it worked wonders. The vent cost 19 bucks and it is worth the investment for sure.

Agree. If the plumbing system is properly installed and vented, you do not need any additive to the holding tanks. Additives, like RV toilet paper, do nothing but increase revenue for the manufacturer.

[Stampedelady]

It seems none of you have given the answer that usually holding tanks don't smell at all unless there is a problem with them.. this person does not say which holding tank so I will start with the grey water. Add vinegar and bleach to your grey tank and fill to about 1/3.. drive for a few hours, empty.. use as normal. Secondly the black water WILL smell if it does not empty fully. Never empty your black tank until it is full but it could be that in the past it has been left to dry to the sides( the feces) and it has clogged the tank. Try 3 or 4 bags of ice.. 10 gallons of water and drive for a few hours. You might need to do this a few times to really clean the tank.. then deodorise as normal. Make sure you use an enzyme deodorant..

[myredracer]

An RV holding tank and the waste piping is a sealed system as far as air goes. Each tank is supposed to have it's own vent to the roof. Each vent will equalize the pressure to the air pressure outside. If there's a rush of air into the tank, it will get pushed up through the vent pipe and go outside. When draining the tank(s), air will be drawn into the tank(s). Providing the P-traps have water in them and seals are not leaking, unless there is a crack in the piping or a fitting has come apart or a tank has a crack or puncture, you should not get on-going odors inside the RV. Same way a septic disposal system works in residential use.

An air-admittance (one-way) valve is sometimes used if the vent pipe to the roof is too far away from a sink. You can unscrew it, clean off the goop if any is on it, and suck and blow on it to check it. IIRC, these are supposed to be installed 4-6" above the top elevation of water in a P-trap, but you may want to google this. As we all know, a factory can *occasionally* install something wrong.... It should be easy to raise the height of one by modifying the piping with a couple of elbows. Even if it looks okay, it can't hurt to try and raise it if you have persistent odor problems there.

I don't quite see why you would need a Lil' Stanker fan or other device if all of your plumbing is in good order and originally installed properly. Can't hurt to try it of course. I spent every summer as a youth at my parents cabin that had an outhouse. The occasional whiff of sewer odor isn't really offensive to me since we are "camping". I suppose it may be bothersome to some folks though. I guess a MH is more likely to have odor issues if plumbing fixtures are used while in transit? Can't see how one of those tornado roof vents would help on a black tank since it can't draw air out of the tank except when the toilet valve is momentarily open.

There is always the possibility of the worse case scenario. I have read numerous posts on various forums about RV owners that have ended up with cracked pipes and fittings, separated fittings and even failed tank support straps. Sometimes a fitting may not have been glued together properly at a factory and leak or even come apart. Besides bad odors, if you have an insulated underbelly, the insulation can get soaked, leading to a lot of repair work. Occasionally, piping simply isn't installed properly to start with. What if they missed putting in a P-trap somewhere like under a shower? If any error *can* happen, it's probably happened to someone before.

If you travel a lot full water in the tanks, that causes stress on the tank support straps and their attachments to the frame. Some RVs are built well enough to handle this and some just aren't. Sometimes you can exceed the RV's GVWR significantly too (just one full tank would put us over). I think more stress could occur from travelling with partial tanks due to the weight of water sloshing back and forth. More likely to happen with fresh water tanks, but if you're dry camping or at a cg without sewer hookups, I'd want to always dump at the closest dump station to play it safe. If you end up with failed support straps, fittings can pull apart. If you see water under your unit where it shouldn't be or the underbelly seems to be sagging more than it should, you may want to investigate.

A week ago while beginning a 2 week camping trip, we had odors under the kitchen sink which I suspect was from the grey water. Checked the air valve, made sure the P-trap wasn't clogged and looked for anything wrong. Sprayed disinfectant inside the cabinets and cleaned it all out. Odors have not returned. I did notice while in there, there is quite a gap around the piping through the floor and I could feel air blowing through. Not a good thing so sealing the gap up would probably help.

[binspector]

I put one of these on my black tank and one on my grey tank.
Awesome!!!!!
https://360productsnorthamerica.com/site/testimonials

[JFXG]

bj32, I just read through this whole thread, and if I'm not mistaken nobody has welcomed you to iRV2! So, Welcome!!

Also, unless I overlooked something, its not clear exactly how you use your motorhome. The difference between intermittent use and full-timing will significantly change the way you have to treat your tanks on an ongoing basis.

[mel s]

Originally Posted by Stampedelady

It seems none of you have given the answer that usually holding tanks don't smell at all unless there is a problem with them.. this person does not say which holding tank so I will start with the grey water. Add vinegar and bleach to your grey tank and fill to about 1/3.. drive for a few hours, empty.. use as normal. Secondly the black water WILL smell if it does not empty fully. Never empty your black tank until it is full but it could be that in the past it has been left to dry to the sides( the feces) and it has clogged the tank. Try 3 or 4 bags of ice.. 10 gallons of water and drive for a few hours. You might need to do this a few times to really clean the tank.. then deodorise as normal. Make sure you use an enzyme deodorant..

The fact is that the contents of both sewer tanks SMELL, unless you get them as clean as a fresh water tank and never use them....(it's SEWAGE after all).

Those containing sewage smell like SEWAGE and those with treated with chemical additives smell like "SEWAGE WITH A CHEMICAL PERFUME ADDED".
The only "trick/method" that actually WORKS is: DO NOT not let tank odor get INTO your RV.

IMO, far to much emphasis is placed on trying to coverup or eliminate the odor in the tank and not enough on preventing the odor of sewage in the tanks from getting into the RV.

If you do things right and nothing is wrong/broken, the smell does not get into the living area of RV.
In other words, if the drain and vent systems are operating properly the stink CAN NOT/WILL NOT enter the RV.

Mel
'96 Sahara, Rid-X, (NO deodorant)....
NO ODOR IN THE RV CABIN for 12 years.

[mel s]

Originally Posted by binspector

I put one of these on my black tank and one on my grey tank.
Awesome!!!!!
https://360productsnorthamerica.com/site/testimonials

binspector
Where does the "make-up air" get into the tanks that those "magic vent caps" supposedly suck/vacuum out?
How can they break a law of physics and/or the rules of air flow/venilation?

Did you ever suck the air out of a soda bottle?
What happened when you did?

Think about it!

Mel
'96 Safari

[IndianaJoe]

I installed a Cyclone vent on my motorhome and it works very well. I believe it is worth the 20 bucks you will have to pay for one.

[gemini5362]

The biggest problem we see is caused by the vent fan in the bathroom ceiling. If we go to flush the commode and have the fan on then the fan has a tendency to pull the gases out of the black tank. We either make sure to shut the fan off before flushing or to open the bathroom window a bit so that we do not have a negative pressure above the commode when we flush. We also use Break Away treatment in the tanks. My wife likes that the best of the brands we have tried.