Holding tank venting

We’ve been blessed with a well-operating holding tank system, no leaks or bad odors. We flush a packet every weekend of use, and that has seemed to keep things in order.

However, we recently mistakenly overfilled the tank, and after pumping out, we now find that there’s a venting of very bad odor outside every time we flush. Even multiple rinses, pump outs, and packet flushes have not resolved this. My suspicion is we somehow stirred up or activated some sludge that had previously been buried in the bottom.

Sorry for the unpleasant descriptions. My question is: is there something we can do, perhaps a more powerful additive, to “reset” the tank and tamp down the fumes? The integrity of system is still fine, no internal leaks. It’s just that there’s clearly a much more potent gas in there that gets vented now.

Back flush your vent line? Is there s filter in place that got wet?

Peggie Hall will probably be around soon and put her finger on it!!!!!

Sounds like ur holding tank vent filter may have gotten wet. You may want to try replacing it to see if that resolves the odor issue.

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schrater said:

We’ve been blessed with a well-operating holding tank system, no leaks or bad odors. We flush a packet every weekend of use, and that has seemed to keep things in order.

However, we recently mistakenly overfilled the tank, and after pumping out, we now find that there’s a venting of very bad odor outside every time we flush. Even multiple rinses, pump outs, and packet flushes have not resolved this. My suspicion is we somehow stirred up or activated some sludge that had previously been buried in the bottom.

Sorry for the unpleasant descriptions. My question is: is there something we can do, perhaps a more powerful additive, to “reset” the tank and tamp down the fumes? The integrity of system is still fine, no internal leaks. It’s just that there’s clearly a much more potent gas in there that gets vented now.

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First, I would recommend you purchase and read Peggie Hall’s book.

https://tinyurl.com/y7b3ltjh

As was mentioned, you could have forced holding tank contents into the holding tank vent. If there are any low spots in the vent line (like on my boat that I haven’t fixed yet) they you can get the smelly stuff pooling there. Every time you flush, the vented air then bubbles through that smelly stuff.

Alternatively, you may have a vent filter. A vent filter is usually a carbon filter that is used to try and reduce tank odors through the vent. Unfortunately, the vent filter reduces the amount of O2 exchange which can make your tank smell. If it gets holding tank contents in it, by overfilling your tank, then it will smell.

What is a “packet” you mentioned?

My own ignorant suggestions would be to trace the vent line in your holding tank and see if you have an inline filter. If you do, I would recommend you remove it. If you don’t have an inline filter, then I would recommend that you back-flush your holding tank vent while you pump out the holding tank. Likely there are holding tank contents in the vent and back-flushing the vent may clear that out. Even if you use a service to pump out your holding tank, I think you should do it yourself several times a year so that you have the opportunity to back-flush the vent line.

There is sewage in the hose connecting the holding tank to the vent. Replace that hose.

Backflushing a vent line that’s trapping should be followed by a blast of air, as the flush water will also be trapped in the line until it is rerouted to a positional where it will drain back into the tank.
The tank must breathe, and will continue to emit foul odors until it can breathe freely.
If the vent line takes a long horizontal run, you’ll need to reroute it or take great care to insure that it runs at least slightly uphill all the way to the vent.
Sometimes a section of solid pipe,ABS or PVC is needed to accomplish that.

Suggest you replace the vent filter and or material first, will most likely solve your problem.

I'd start with removing any vent filter (if installed) and blow out the vent line from outside to inside!

Don't let any of these wiseguys talk you into sucking on the vent line. A friend told me that it doesn't work and it's hard to get the taste out of my mouth.

Peggie Hall will probably be around soon and put her finger on it!!!!!

Others have already said just about everything I'd have said (apparently I've trained 'em pretty well!).

However, if there is a filter in the vent line I wouldn't replace it. Instead, I'd shorten and straighten the vent line as much as possible--keeping it as close to horizontal as possible--and replace the vent thru-hull with any open "bulkhead" thru-hull that'll allow enough air exchange with the gasses in the tank to keep it aerobic, eliminating the need for a filter by preventing odor from occurring. An open thru-hull also provides another advantage: you can put a hose nozzle against it and backflush the vent line every time you wash the boat, preventing vent from ever becoming blocked. All this is explained in detail in my book (see link in my signature...just click on the title) and I'm always glad to answer any questions it doesn't.

And I am curious to know what product is in the packets you've been using.

--Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

We’ve always flushed “Camco TST Ultra-Concentrated Orange Citrus Scent RV Toilet Treatment Drop-Ins”. Maybe just placebo effect, but it’s always worked well for us.

Gmarr said:

Back flush your vent line? Is there s filter in place that got wet?

Peggie Hall will probably be around soon and put her finger on it!!!!!

Click to expand...

An elegantly rubber gloved finger though, I`m sure.

schrater said:

We’ve always flushed “Camco TST Ultra-Concentrated Orange Citrus Scent RV Toilet Treatment Drop-Ins”. Maybe just placebo effect, but it’s always worked well for us.

Click to expand...

It's not a placebo, but like most other RV tank products, it's a chemical product, and formaldehyde isn't the only nasty chemical. The active ingredient in TST is Calcium Nitrate Tetrahydrate that, according to the MSDS TST RV Toilet treatment MSDS can be harmful to aquatic life. And I'm not fond any tank product that carries these first aid warnings:

"This product may be harmful or fatal if swallowed. If ingested, this product will immediately cause burns to the mouth, throat, esophagus and possibly the digestive tract. Ingestion can cause gastrointestinal irritation, nausea, vomiting and diarrhea. This product may cause methemoglobinemia upon ingestion characterized by cyanosis, headache, dizziness, fatigue,nausea, vomiting, drowsiness, stupor, coma and rarely death. Potential Health Effects: Inhalation
This product is irritating to the respiratory system. Inhalation of vapors or mists of the product can cause sneezing, coughing and difficulty breathing."


Chemical tank products are popular because they're the least expensive, but they try to eliminate odors AFTER they're generated--the product description for TST says fragrances are added to eliminate (or perhaps mask?) odor--instead of working WITH nature to create the conditions in which organic matter (waste) breaks down aerobically, producing CO2 which is odorless, instead of smelly toxic gasses (hydrogen sulfide and sulfur dioxide) that can only be generated in anaerobic conditions.

So once you've solved the odor problem created by your tank overflow, I suggest you try another product that works with nature instead of trying to defeat it. Odorlos Odorlos is one...its active ingredient is nitrates which promote oxygen release from the waste itself...and is available from RV supply stores for a lot lower price than any marine retailer. Another is No-Flex Digestor Noflex Digestor, which is relatively new and gets rave reviews from everyone who's tried it.


--Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

Hi Peggie
Just found this post and was looking at the MSDS for the TST
It does't have the proper identifiers warnings

Also out of date 2013
MSDS sheets are only valid for 4 years. Most Governmental agencies request it every 2 years .MSDS should be all but gone now They are now called just SDS and about 14 pages long . Very intense; U.N. world wide controlled.

Doesn't say much that's good about the mfr's quality control, does it?


--Peggie

Assuming our son continues to mend (and we got good reports this morning), I will eventually get back to work on our new boat. Survey said "Fiberglass holding tank". Not. Metal, with a coating that I must admit looks like fiberglass. So in addition to taking out the two Galley Maid toilets and all sanitation hoses, I plan to remove the 35 gal holding tank (it's actually very accessible) and replace with a 60 gal Ronco tank - yes, there is room. I have specked two 1 1/4" vent line openings which I can easily vent out each side of the engine room, to give me lots of 'flow through oxygen'. And yes, I have the Head Mistress's book

FoxtrotCharlie said:

Assuming our son continues to mend (and we got good reports this morning), I will eventually get back to work on our new boat. Survey said "Fiberglass holding tank". Not. Metal, with a coating that I must admit looks like fiberglass. So in addition to taking out the two Galley Maid toilets and all sanitation hoses, I plan to remove the 35 gal holding tank (it's actually very accessible) and replace with a 60 gal Ronco tank - yes, there is room. I have specked two 1 1/4" vent line openings which I can easily vent out each side of the engine room, to give me lots of 'flow through oxygen'. And yes, I have the Head Mistress's book

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Hope things improve for your son.

Sounds like your plan is exactly right. 2 large vents into a Ronco tank will be good.

Before installing the new larger tank, you might add an airator bar as low inside as is practical.

The Euro charter buckets tie up stern too , so many waste vents can end up sending sewer gasses up to the next boat.

Using a tiny air compressor ,as found in a fish tank, can increase the air flow enough to stop the poo stink.

With some charters at $10,000 to $30,000 a day it does make a difference.

Here is one I assembled around a 12v air pump bait aerator. My holding tank already had a cleanout/inspection cover. The pump is available at many fishing tackle sellers.

Steve said:

Here is one I assembled around a 12v air pump bait aerator. My holding tank already had a cleanout/inspection cover. The pump is available at many fishing tackle sellers.

Click to expand...

Steve
I have seen your photos before and like your set up.
Just wondering if you have had any problems w/ your "stone" aerators plugging?
I did a similar DIY system but didn't bother w/ an exotic distribution end - it seems to be working fine but wondered about yours.

Thanks

Greetings,
Mr. B. "... "stone" aerators plugging?" I thought of exactly the same thing. During my "aquarium" days I found, that the "stones" tended to clog and this was in relatively clean/pristine water. In spite of the fact that the small bubbles will initially provide much more air surface area, perhaps large bubbles produced by an open ended tube would supply enough as compared to a slowly clogging "stone".

I put the aerator in in 2010 after a couple of years I took it out and hosed it off. the stones were not plugged, but I replaced them anyway. the ones, (same kind as in picture) I put on then are still working fine. When I installed it I worried they would plug so bought a small ring aquarium aerator with larger holes but it is still unused. No doubt just the tubes would work also, if I were to start having problems with the stones plugging I could pull them off.
This is a home made copy of the "Sweet tank" system, more details can be seen here https://www.groco.net/products/marine-sanitation/sweet-tank-odor-prevention

You may have to sigh up, but here is a way to build your own vent filter instead of paying $100 for one.

http://www.boatinghowto.com/content/building-holding-tank-filter-288/

Bacchus said:

Steve

I have seen your photos before and like your set up.

Just wondering if you have had any problems w/ your "stone" aerators plugging?

I did a similar DIY system but didn't bother w/ an exotic distribution end - it seems to be working fine but wondered about yours.

Click to expand...

My question as well. I considered doing exactly what Steve did, but was concerned about the stones plugging and then the hassle of replacing them or maintaining them.

Edit: I see Steve hasn’t had an issue. I’m already to setup without them. That will be this weekends project unless we take advantage of the nice weekend and take off in the boat.

Dave
FYI I have found it best to run the pump 24/7. At first I tried shutting down o'nite but think it is better on full time.
I can't see where a dip tube w a T and capped ends w a few small holes would be a problem if the stones plug.
If good vents providing sufficient air above the surface works why wouldn't a single stream of air bubbles?

The Groco Sweetank has a hose that lays in the bottom of the tank and has lots of holes in it. I used one in a previous boat with excellent success. I think that even pumping air into the holding tank might work just fine without the hose for air distribution but I am not sure. It would certainly work better than just a small vent, or certainly way better than a small vent with a filter in it. I would never have a filter in the vent.

Bacchus said:

Dave
FYI I have found it best to run the pump 24/7. At first I tried shutting down o'nite but think it is better on full time.
I can't see where a dip tube w a T and capped ends w a few small holes would be a problem if the stones plug.
If good vents providing sufficient air above the surface works why wouldn't a single stream of air bubbles?

Click to expand...

That was my thought as well. I kept thinking about how to get more widely dispersed bubbles, small enough bubbles etc... It finally dawned on me that the reason I am doing it at all is that I can't easily install two decent sized air vents. All the air vents would do is passively exchange the air in the head space above the tank contents. The pump will exchange more air in the tank than passive vents and any bubbling effect will cause some motion in the tank contents and give far better oxygenation of the tank contents than simply two good vents.


I'm still considering a timer on the pump. There is a simple and cheap 12v programmable timer that I can set for just about any on/off pattern. I was thinking going for a 50% duty cycle such as 30 minutes on, 30 minutes off. That would cut the amp draw in half and should extend the life of the pump.

The current draw on the Groco Sweetank pump was negligible so I did run mine continuously.

Comodave said:

The current draw on the Groco Sweetank pump was negligible so I did run mine continuously.

Click to expand...

Yeah, The pump I'm using (the same as Steve and Bachus I think) claims a 1/2 amp.

Dave
I had the same thoughts re timer but never found one that would give me 50% or less duty cycle and I found constant on not a problem. I'm on my origonal pump and it's still going. I figure easier to change a pump than mess w a timer.
Amp draw is insignificant.

The other reason I didn’t want to turn off the pump is that I was concerned that sewage may backup into the air tube and plug it up. Last thing I wanted to work on was a air hose that had been living in the poop...