Holding Tank Vent Filter

[Ray.Yager]

Searching for an in-line filter on my holding tank vent. The two holding tanks are on either side of the aft-cabin bed. The only access that I’ve found to the tanks matches up with the inspection port. So, I can’t see any of the hose connections let alone an in-line filter. I did find the hose connection to the thru-hull. It was behind the aft port corner trim piece behind a speaker.

Is it possible that there never was a filter on the vent lines?

 

[dhays]

Searching for an in-line filter on my holding tank vent. The two holding tanks are on either side of the aft-cabin bed. The only access that I’ve found to the tanks matches up with the inspection port. So, I can’t see any of the hose connections let alone an in-line filter. I did find the hose connection to the thru-hull. It was behind the aft port corner trim piece behind a speaker.



Is it possible that there never was a filter on the vent lines?

Not sure about your boat, but it would be very likely that it doesn’t have a vent filter. In general, I think they are a bad idea.

 

[Ray.Yager]

So, you prefer a chemical treatment instead?

What are the cons to vent filters?

 

[dhays]

So, you prefer a chemical treatment instead?

What are the cons to vent filters?

The best way avoid holding tank odors is to provide lots of oxygen to the tank to encourage the growth of aerobic bacteria as opposed to the anaerobic bacteria which smells bad. Vent filters reduce the air flow through into the tank. They also can get clogged which can make it harder to pump out the tank.

As for tank treatment, I have used Raritan K.O., No-Flex, or simple sodium percarbonate. The KO, as I understand it, introduces health aerobic bacteria to the tank so if you have enough air exchange it works really well. No-Flex and sodium percarbonate introduce oxygen to the holding tank as is breaks down.

I eventually made and installed a tank aerator to provide good air exchange in the tank. That is by far the best solution.

There are others much smarter than I on this. You may try doing a search for threads on holding tank vents and you will get lots of information.

https://www.amazon.com/New-Get-Rid-...=1&keywords=Peggie+hall&qid=1627752699&sr=8-1

That is the best resource available for holding tank issues.

 

[Constellation1]

Hi Ray - I highly recommend you read Peggie Hall's book 'Get rid of boat odors'. Peggie is the Guru of boating sanitation and a wonderful person. She addresses the cons of holding tank vent filters well in her book. She is also frequently online her on TF - HeadMistress is her username.

 

[Dwk]

Vent filters restrict aerobic bacteria that is essential in holding tanks. The more air coming in the better the bacteria grows.Filters are suppose to cause less odor exiting your tank,so they say. Ditch the filter and allow the air to flow.

 

[Dwk]

Hi Ray - I highly recommend you read Peggie Hall's book 'Get rid of boat odors'. Peggie is the Guru of boating sanitation and a wonderful person. She addresses the cons of holding tank vent filters well in her book. She is also frequently online her on TF - HeadMistress is her username.

I also recommend Peggies book,great practical knowledge.

 

[HeadMistress]

A little bio-physics 101: When organic matter breaks down AEROBICALLY (oxygenated) it converts to CO2 which is odorless. When it breaks down ANAEROBICALLY it generates hydrogen sulfide and sulfur dioxide which not only stink but are also toxic, and methane which is odorless but flammable. Vent line filters actually help to create the very problem they're sold to so solve because they impede the exchange of oxygen with gasses in the tank that's essential to PREVENTING odor by simply blocking odor. The tank product used matters, but improving the ventilation to the tank is the key eliminating holding tank odor--odor out the vent---because oxygen prevents it from occurring in the first place.


Thanks for all the "plugs" for my book! Its title (my publisher's idea) is a bit misleading...'cuz although it does deal with every source of odor on a boat and how to cure, or better yet PREVENT 'em, it's actually a comprehensive "marine toilets and sanitation systems 101" manual that explains the laws, describes all the types of systems and how they work, and will help you learn how to operate and maintain your system to prevent 99% of problems instead of having to cure 'em. 'Cuz you get to do any preventive maintenance on your terms when it's convenient...the need to cure a problem never happens when it is! And I'm always glad to answer any questions it doesn't.

--Peggie

 

[Bacchus]

IMO vent filter ENSURE that your tank will be anaerobic (the smelly kind) and your tank will smell bad. Then you NEED the filter to prevent the escape.
A better approach is to ensure aerobic (not smelly) bacteria predominate and there is no need / use for a filter.
Large, short, straight vent line & straight thru mushroom fitting alow the most air flow.
NoFlex or generic sodium percarbonate (a little each day) has workedwell for me.
I built & installed a DIY bubbling system for about $40 and it has worked perfectly.
See Bacchus Website... Project.... DIY Holding Tank System for details.

 

[Ray.Yager]

All righty then. I just flushed a couple of Tbls of Noflex in each head. Will do so again tomorrow to make sure it made it makes it past the vacuflush tank. Will see if my dock neighbors are happy.

WE get pumped out every Wednesday and we use only fresh water. I’m thinking the Noflex should keep my neighbors happy.

 

[Martin J]

3-4 months ago I installed a 12v air pump (think fish tank) to avoid odors when pumping at sea. Super oxygenating the waters promotes good bacteria ergo no odors. After a few days there was a slight smell on the vent area of the tank. That has now disappeared. So it looks like some success has been achieved. I have a 100gall holding tank. My previous boat was always a tad odorous when offshore pumping at sea. The whole thing only took a few hours to fabricate.

 

[HeadMistress]

All righty then. I just flushed a couple of Tbls of Noflex in each head. Will do so again tomorrow to make sure it made it makes it past the vacuflush tank. Will see if my dock neighbors are happy

Unlikely if flushing No-Flex is the only thing you've done.



--Peggie

 

[Comodave]

Yes, if you have a vent filter get rid of it and maybe add a second vent. That will help get oxygen into the tank.

 

[SteveK]

The best way avoid holding tank odors is to provide lots of oxygen to the tank to encourage the growth of aerobic bacteria as opposed to the anaerobic bacteria which smells bad. Vent filters reduce the air flow through into the tank. They also can get clogged which can make it harder to pump out the tank.

As for tank treatment, I have used Raritan K.O., No-Flex, or simple sodium percarbonate. The KO, as I understand it, introduces health aerobic bacteria to the tank so if you have enough air exchange it works really well. No-Flex and sodium percarbonate introduce oxygen to the holding tank as is breaks down.

I eventually made and installed a tank aerator to provide good air exchange in the tank. That is by far the best solution.

Dave, with the aerator are you still using a chemical treatment? Not using the chem would be the only reason for me. Peggy has said vent on either side and 2 inch lines IIRC. Again, can chemicals be eliminated with aeration methods.

 

[Comodave]

We put a Groco Sweetank system in a previous boat on Peggies advice. We never put any chemicals in after that for the 8 more years we owned the boat.

 

[backinblue]

A little bio-physics 101: When organic matter breaks down AEROBICALLY (oxygenated) it converts to CO2 which is odorless. When it breaks down ANAEROBICALLY it generates hydrogen sulfide and sulfur dioxide which not only stink but are also toxic, and methane which is odorless but flammable. Vent line filters actually help to create the very problem they're sold to so solve because they impede the exchange of oxygen with gasses in the tank that's essential to PREVENTING odor by simply blocking odor. The tank product used matters, but improving the ventilation to the tank is the key eliminating holding tank odor--odor out the vent---because oxygen prevents it from occurring in the first place.


Thanks for all the "plugs" for my book! Its title (my publisher's idea) is a bit misleading...'cuz although it does deal with every source of odor on a boat and how to cure, or better yet PREVENT 'em, it's actually a comprehensive "marine toilets and sanitation systems 101" manual that explains the laws, describes all the types of systems and how they work, and will help you learn how to operate and maintain your system to prevent 99% of problems instead of having to cure 'em. 'Cuz you get to do any preventive maintenance on your terms when it's convenient...the need to cure a problem never happens when it is! And I'm always glad to answer any questions it doesn't.

--Peggie

Hi Peggie. I've been using this stuff, Is this good or bad?


https://www.amazon.com/dp/B077VWX6BB?psc=1&ref=ppx_yo2_dt_b_product_details

 

[HeadMistress]

Peggy has said vent on either side and 2 inch lines IIRC. Again, can chemicals be eliminated with aeration methods...

You recall incorrectly. I'm misquoted on this more than anything else.

I have said that 2 vent lines MAY be advisable in installations that make it impossible for 1 vent line to provide necessary ventilation, but I've never recommended a 2" vent line nor insisted that it has to exit on both sides of the boat. A single 1" vent line or at most a 1.5" in a short (up to 5') straight line that has no more than a 45 degree rise to an open bulkhead or "mushroom" thru-hull is enough to do the job one most boats. There are a few installations that won't allow anything but aeration to work.

--Peggie

 

[HeadMistress]

Hi Peggie. I've been using this stuff, Is this good or bad?

https://www.amazon.com/dp/B077VWX6BB?psc=1&ref=ppx_yo2_dt_b_product_details

If you're happy with it, it's your boat. However, I'm automatically skeptical of any product that refers to a holding tank as a septic tank (anaerobic, the opposite of aerobic). More importantly, that it's a chemical product that the mfr touts only as "non-formaldehyde" is a big red flag for me 'cuz formaldehyde is just one of the toxic chemicals used in tank products...quaternary ammonium compounds and gluteraldehyde are the other most commonly used highly toxic chemicals...all of which work by killing bacteria, which is not what you want to do.

And btw.."biodegradeable" is actually a meaningless feel-good term typically used to mislead people into confusing it with "environmentally friendly"...formaldehyde is actually biodegradable, it just takes a quite a while TO biodegrade, doing considerable environmental harm meanwhile. I'd need to see the SDS for this product to know what "non-formaldehyde" chemical is the active ingredient and what else is in it that could potentially harm the plumbing or may be unsafe to store around children or pets.

--Peggie

 

[SteveK]

Peggy has said vent on either side and 2 inch lines IIRC. Again, can chemicals be eliminated with aeration methods...

You recall incorrectly. I'm misquoted on this more than anything else.

I have said that 2 vent lines MAY be advisable in installations that make it impossible for 1 vent line to provide necessary ventilation, but I've never recommended a 2" vent line nor insisted that it has to exit on both sides of the boat. A single 1" vent line or at most a 1.5" in a short (up to 5') straight line that has no more than a 45 degree rise to an open bulkhead or "mushroom" thru-hull is enough to do the job one most boats. There are a few installations that won't allow anything but aeration to work.

--Peggie

Thanks for the correction.
Cross contamination is what it is. Following to the groco site shows a 'T' vent line, did not look for size. Steve D'Antoni has an article that suggest two lines up to 1-1/2. So the info goes in and gets mixed up.

If passive air from a 1" single line does the job in the air space above sewage, then why bother installing a bubbler like Groco and not as suggested just plumb to top a fish tank aerator of tank to keep moving fresh air?

 

[backinblue]

If you're happy with it, it's your boat. However, I'm automatically skeptical of any product that refers to a holding tank as a septic tank (anaerobic, the opposite of aerobic). More importantly, that it's a chemical product that the mfr touts only as "non-formaldehyde" is a big red flag for me 'cuz formaldehyde is just one of the toxic chemicals used in tank products...quaternary ammonium compounds and gluteraldehyde are the other most commonly used highly toxic chemicals...all of which work by killing bacteria, which is not what you want to do.

And btw.."biodegradeable" is actually a meaningless feel-good term typically used to mislead people into confusing it with "environmentally friendly"...formaldehyde is actually biodegradable, it just takes a quite a while TO biodegrade, doing considerable environmental harm meanwhile. I'd need to see the SDS for this product to know what "non-formaldehyde" chemical is the active ingredient and what else is in it that could potentially harm the plumbing or may be unsafe to store around children or pets.

--Peggie

I'm not particularly attached to this product other than its ease of use. I'd be very interested in what you think is the best additive to use. I had a new holding tank installed 2 years ago, so it should be in fairly good shape for whatever is advisable. I have a vent and no filter, but my wife sometimes complains of odor. Unfortunately (sometimes fortunately) I have lost my sense of smell in recent years so I rely on her feedback. And of course I trust whatever you think is best. Thanks for your help!

 

[HeadMistress]

If passive air from a 1" single line does the job in the air space above sewage, then why bother installing a bubbler like Groco and not as suggested just plumb to top a fish tank aerator of tank to keep moving fresh air?

Why would you need any aerator unless passive ventilation isn't working???

--Peggie

 

[HeadMistress]

I'm not particularly attached to this product other than its ease of use. I'd be very interested in what you think is the best additive to use.

No-Flex Digestor is the top rated product and the one I recommend.

I have a vent and no filter, but my wife sometimes complains of odor.

Inside the boat? Out the vent? Or both? Odor inside the boat is an entirely separate issue from odor out the vent and each requires a different solution.

--Peggie

 

[dhays]

Dave, with the aerator are you still using a chemical treatment? Not using the chem would be the only reason for me. Peggy has said vent on either side and 2 inch lines IIRC. Again, can chemicals be eliminated with aeration methods.

I don’t use anything if I have kept the aerator running. If I will be away from the boat for a while I will sometimes turn it off just to save wear and tear on the air pump. However, Bacchus is using the same pump as I am and had run it 24/7 for years with no issue.

Anyway, if the air pump has been off for a while, I will use No-flex when getting back to the boat initially and turn on the pump.

 

[dhays]

I have said that 2 vent lines MAY be advisable in installations that make it impossible for 1 vent line to provide necessary ventilation, but I've never recommended a 2" vent line nor insisted that it has to exit on both sides of the boat. A single 1" vent line or at most a 1.5" in a short (up to 5') straight line that has no more than a 45 degree rise to an open bulkhead or "mushroom" thru-hull is enough to do the job one most boats. There are a few installations that won't allow anything but aeration to work.

In my case, I changed the screened cowl type vent cover with an open mushroom through hull first, and then add aeration. The 1” (or was it 3/4”?) vent line was really long, and didn’t have a nice even rise. The holding tank is located right in the center of the boat with no easy way to improve the venting. We didn’t have too huge a problem with odor but it was enough that when the toilet was flushed there would sometimes be a foul odor outside the boat. In the summer with the windows open it would drift inside. It bothered by wife. Adding an aerator was super easy compared to improving the venting.

 

[Comodave]

In some boats an aerator is much easier to do than reworking the vents. We have put aerators in 2 boats and had great success with them. We didn’t use any chemicals in the tank after installing the aerator and just left it running 24x7. Our new boat will either get 2 new vents or an aerator. Have not had a chance to see what access there is to the holding tank yet.

 

[backinblue]

I'm not particularly attached to this product other than its ease of use. I'd be very interested in what you think is the best additive to use.

No-Flex Digestor is the top rated product and the one I recommend.

I have a vent and no filter, but my wife sometimes complains of odor.

Inside the boat? Out the vent? Or both? Odor inside the boat is an entirely separate issue from odor out the vent and each requires a different solution.

--Peggie

Thanks Peggy, I ordered some No-Flex to try. I'm not postive, but I think the odor is most noticebale when flushed so I am assuming it's coming out the vent, at least mostly. The boat and systems are less than 10y years old, the tank ony 2 years old, so I'm assuming it's not something like hoses or crud buildup in the tank.

 

[Choices]

I have the same issue of a odor on using vacuflush. Odor is inside and at vent.

I am replacing hatch gaskets to contain smell.

I think I have an airleak at the holding tank. Once I fix that may add a bubbler system for extended time on the boat.

We add a little Oxyclean or Tide with each flush. I am cleaning holding tank well after each emptying.

It is nice to have Peggy on the forum. Cuts through the BS.

 

[backinblue]

hmmm, there should be no air leak at the tank. Couldn't that lead to sewage leakage when sloshing around? That's why I had to replace my tank. It was cracked and leaking around one of the fittings. You might find it by emptying the tank and filling it with fresh water through the pump out and look for leaks in the tank and around hose fittings. That's how mine was found.

 

[HeadMistress]

I'm not postive, but I think the odor is most noticebale when flushed so I am assuming it's coming out the vent, at least mostly.

If it's inside the boat, it's not coming out the vent, which means the tank isn't the source. If it's outside the boat, it can only be coming out the vent from inside the tank.If you have odor inside the boat AND out the vent, you have TWO sources of odor, each of which must be dealt with separately.

So let's start with eliminating the odor inside the boat. Permeated hoses are the most common source and the age of the hose is not a reliable indicator...So hoses on my own boat permeated in less than 90 days. There's a simple test: Wet CLEAN rags in HOT water--as hot as you can handle. Wrap each section of hose a clean rag...let it cool, then remove each rag and smell it. If you can't smell anything on that rag, that section of hose is ok...but if you can, that hose has permeated. If they all pass the test, the previous hoses could have transferred odor to the lockers/areas they passed through and everything in them.

Crud buildup in a tank is NOT a source of odor out the vent. In adequate ventilation causes that.

--Peggie

 

[HeadMistress]

I have the same issue of a odor on using vacuflush. Odor is inside and at vent.

Start by seeing my reply to Backinblue.

I am replacing hatch gaskets to contain smell.

I'm pretty sure you're actually mean you're attempting to contain odor inside the boat to the inside of a locker...but why would you want to do that instead of eliminating the odor???

It's highly unlikely that you have an air leak at the tank...air leaks only occur in the plumbing between the bowl and the vacuum pump...the holding tank isn't part of VacuFlush. I'll be glad to send you--and anyone else who'd like to have it) my article "VacuFlush 101" which explains how the VF works if you'd like to send me a PM that includes your email address (no way to attach anything to a PM). If you had a leak at the tank you'd see visible evidence of it at a fitting or a crack in the tank.

We add a little Oxyclean or Tide with each flush.

They might prevent animal fat build up on tank walls and any tank level sensors inside the tank, but won't do a thing to prevent odor out the vent. Start using a real tank product...No-Flex Digestor Noflex Digestor is the top rated product and the one I recommend.

I am cleaning holding tank well after each emptying.

Just rinsing it out with a few gallons of water in the tank using a hose nozzle via the deck pumpout fitting is all that's needed...a more thorough rinse in preparation for winter or other extended layup.

As for your odor inside the boat...permeated hoses and/or residual odor left in lockers that stinky hoses passed through are the most likely source, but not the only possible source. A wet bilge in need a SERIOUS cleaning instead of just dumping something in the bilge and letting it slosh around for a while is also a likely culprit.

At the risk being accused of attempting to sell you something, both you and Backinblue NEED my book (see link in my signature below, just click on the title)...especially the section that deals with odors inside the boat AND holding tank maintenance and odor out the vent.

--Peggie