Holding tank

We have a Mainship 400 which is located at a marina. We occupy it on the weekends but do not utilize the head on a regular basis. Any suggestions on how to eliminate the strong pungent smell that it produces on regular weekend flushes for maintenance to circulate water. We always use the marina restrooms.

Any feedback is appreciated.

You need more air flow in the holding tank. Check your vent, it is probably very small and convoluted which will restrict air flow. Best plan is adding another vent on the opposite side of the boat to allow air to flow through. Anaerobic bacteria is what smells, aerobic bacteria does not. Get Peggie Halls book on boat odors. It is a very good source to all you need to know about heads and related systems.

Get Peggie Hall's book on boat odors. It is a very good source to all you need to know about heads and relared systems.

I can't argue with that advice! You'll find a link to it in my signature below...just click on the title in bold. And I'm always glad to answer any questions it doesn't.

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

Comodave said:

You need more air flow in the holding tank. Check your vent, it is probably very small and convoluted which will restrict air flow. Best plan is adding another vent on the opposite side of the boat to allow air to flow through. Anaerobic bacteria is what smells, aerobic bacteria does not. Get Peggie Halls book on boat odors. It is a very good source to all you need to know about heads and related systems.

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Thank you

HeadMistress said:

Get Peggie Hall's book on boat odors. It is a very good source to all you need to know about heads and relared systems.

I can't argue with that advice! You'll find a link to it in my signature below...just click on the title in bold. And I'm always glad to answer any questions it doesn't.

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

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I appreciate your input

You aren’t drinking enough. I’m pretty sure I pee straight rum. Bacteria can’t survive in my holding tank.

In lieu of a second vent, you can install a Groco Sweetank. That will pump air into the tank and will solve the problem. It maybe a much easier fix than a second vent.

Addendum1 said:

We have a Mainship 400 which is located at a marina. We occupy it on the weekends but do not utilize the head on a regular basis. Any suggestions on how to eliminate the strong pungent smell that it produces on regular weekend flushes for maintenance to circulate water. We always use the marina restrooms.

Any feedback is appreciated.

Click to expand...

Are you flushing with fresh water or salt water?

Comodave said:

You need more air flow in the holding tank. Check your vent, it is probably very small and convoluted which will restrict air flow. Best plan is adding another vent on the opposite side of the boat to allow air to flow through. Anaerobic bacteria is what smells, aerobic bacteria does not. Get Peggie Halls book on boat odors. It is a very good source to all you need to know about heads and related systems.

Click to expand...

+1. Buy Peggie’s book.

My assumption was that you were referring to smell that is expelled overboard when the head is flushed. If you are referring to a smell inside the boat when the head is flushed then the problem likely is a seawater flush and the microorganisms that die inside the intake hose between uses. The easiest fix for that is to go to a freshwater flush head.

Steve91T said:

You aren’t drinking enough. I’m pretty sure I pee straight rum. Bacteria can’t survive in my holding tank.

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[emoji482]

Rain Dog said:

Are you flushing with fresh water or salt water?

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Fresh water

I always turn off
thru hull sea cocks on leaving my boat, then flush well with fresh water, leaving fresh water in the bowl with a little disinfectant added, never had a problem with any of my boats with smell.

Greetings,
We do exactly the same as Mr. ausk. No smells either.

Flush with freshwater.

By freshwater ,they mean water from the boats freshwater tank, not outside freshwater. Just to be sure.

Comodave said:

My assumption was that you were referring to smell that is expelled overboard when the head is flushed.

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This was my assumption as well. I think we need to clarify whether this is an odor in the head and cabin, or whether the cockpit and dock are getting gassed out.

If this is an exterior odor, then this is the displacement of gasses in the holding tank when fluid is flushed into the tank. An in-line holding tank vent filter should be installed. We replace ours roughly every 6 months.

Ahh! I’ve been wondering why sometime when we flush we get a terrible smell outside. Also when we had the boat in Charleston in salt water, the head would stink, especially the first flush after being away for a while. Now that it’s in fresh water, it’s not that bad at all.

All makes sense now.

Addendum1 said:

We have a Mainship 400 which is located at a marina. We occupy it on the weekends but do not utilize the head on a regular basis. Any suggestions on how to eliminate the strong pungent smell that it produces on regular weekend flushes for maintenance to circulate water. We always use the marina restrooms.

Any feedback is appreciated.

Click to expand...

Several folks have mentioned vents and filters relative to exterior odors when you flush.

An easy check is to learn whether you actually have a vent filter, and if you do, when it was last changed. Could be as easy as replacing it with a new one, if it's been a very long time. (We get 3-4 years from our filter.)

OTOH, if you have a filter and if you know it's new, some of the other suggestions may apply... but adding new vents lines and/or increasing vent hose size could be a lot of work... to avoid if you can.

If you mean interior odor when you flush, that's maybe a couple different things. An easy one to check is whether your joker valve needs replacing... and another is about whether hose connections at the head and holding tank are secure.

Also, many folks treat their holding tanks, ideally with products designed to promote and/or sustain aerobic bacteria. Names like NoFlex, KO, Odorlos...

-Chris

Yes if you are flushing with potable water and the smell is external then try using KO. It worked for me.
Once you get it under control dont use bleach or most cleansers in the head they will kill the good bacteria.

As Peggy Hall (head mistress) will tell you an inline vent filter will only add to the problem as it restricts oxygen flow to the tank.

I'm not surprised that Peggy hasn't chimed in after the "dial it back a notch" comment. That comment was uncalled for. Peggy has been nothing but helpful to this forum and whomever made that remark should PM an apology to her. I hope she hasn't given up on us. Howard

Comodave said:

If you are referring to a smell inside the boat when the head is flushed then the problem likely is a seawater flush and the microorganisms that die inside the intake hose between uses. The easiest fix for that is to go to a freshwater flush head.

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Mine does that too....even when isolated from the tank. A regular cleaning of the intake strainer helps. As mentioned, a fresh water flushing system would eliminate that leg of the problem..

hmason said:

As Peggy Hall (head mistress) will tell you an inline vent filter will only add to the problem as it restricts oxygen flow to the tank.

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It must be a valid point, but I have to say we've never really had any odor issues associated with a small-ish factory installed vent hose and a factory installed vent filter. Three boats, three similar systems, no issues.

But it makes me think leaping through that hoop as the first thing to try... is maybe more work than necessary.

I haven't been able to determine whether our KO or NoFlex treatments have had any effect... given no odors when I forget to treat.

-Chris

I'll bet that every time somebody mentions vent filters, Peggy goes outside and yells at the moon or kicks her cat?

Understand the process! With sufficient oxygen, poop doesn't smell.

With insufficient oxygen, it goes anaerobic and it stinks, strong enough to clear out an anchorage.

Get sufficient oxygen into your tank, no STINK. Single 1/2" or 3/4" vents that wend their way through the boat are insufficient. Then, because the poop STINKS, you put a filter on the line? Filtering makes the situation worse.

Install 2 - 1.5" vents or an air pump such that you get tons of oxygen into the tank. No more STINK.

You can stop buying useless, expensive poop vent filters every 6 months and donate the money to a home for bankrupt poop-filter makers.

Enzyme digestors need oxygen too.

Xsbank said:

I'll bet that every time somebody mentions vent filters, Peggy goes outside and yells at the moon or kicks her cat?

Understand the process! With sufficient oxygen, poop doesn't smell.

With insufficient oxygen, it goes anaerobic and it stinks, strong enough to clear out an anchorage.

Get sufficient oxygen into your tank, no STINK. Single 1/2" or 3/4" vents that wend their way through the boat are insufficient. Then, because the poop STINKS, you put a filter on the line? Filtering makes the situation worse.

Install 2 - 1.5" vents or an air pump such that you get tons of oxygen into the tank. No more STINK.

You can stop buying useless, expensive poop vent filters every 6 months and donate the money to a home for bankrupt poop-filter makers.

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Xsbank said:

Enzyme digestors need oxygen too.

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But then there's science, and there's practical/creative laziness.

Theoretically, that's all true. Realistically, I suspect there are a bazillion production boats out there with relatively skinny vent lines and vent filters in place... experiencing no problem at all.

My theory is that one could (and may eventually have to) do a boatload of work to create a theoretically-perfect system... but one could often do quite a bit less work and not notice any need for additional improvement.

Latter probably not applicable in each and every instance, but maybe applicable often enough to make taking the easy road worth a shot first.

In any case, replacing a vent filter every 6 months seems excessive. Our last one lasted 5 years... in a system with only a single skinny vent hose... and no particular odor to speak of. I suspect our experience is fairly common...

Anyway, not disagreeing with the science, of course... just suggesting a whole lot of work isn't always necessary... especially for folks who have "inherited" whatever system came with the boat...

-Chris

bayview said:

Yes if you are flushing with potable water and the smell is external then try using KO. It worked for me.
Once you get it under control dont use bleach or most cleansers in the head they will kill the good bacteria.

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K.O is a great product that works really well. However, you need to have enough O2 in the tank for it to work. Many of us don’t have adequate vents and so the K.O. Will not do its job.

Ultimately, I will most likely install a Sweet Tank system.

dhays said:

K.O is a great product that works really well. However, you need to have enough O2 in the tank for it to work. Many of us don’t have adequate vents and so the K.O. Will not do its job.

Ultimately, I will most likely install a Sweet Tank system.

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FWIW, we used KO for about 15 (almost 20?) years... in boats with skinny vent lines and with vent filters. No odor.

Also no clue whether KO had anything to do with the "no odor" part... since we also didn't have head odors whenever I forgot to treat the tank. Ditto our current use of NoFlex; no odor anyway, so can't tell if NoFlex is doing anything... although at least on (very occasional) sight inspections, there doesn't seem to be any sludge build-up in the tank.

BTW, the only reason we switched from KO to NoFlex is that dosing with the latter is gradual, slightly easier to meter out the product relative to whenever our next pump-out might be...

-Chris

ranger42c said:

FWIW, we used KO for about 15 (almost 20?) years... in boats with skinny vent lines and with vent filters. No odor.

Also no clue whether KO had anything to do with the "no odor" part... since we also didn't have head odors whenever I forgot to treat the tank. Ditto our current use of NoFlex; no odor anyway, so can't tell if NoFlex is doing anything... although at least on (very occasional) sight inspections, there doesn't seem to be any sludge build-up in the tank.

BTW, the only reason we switched from KO to NoFlex is that dosing with the latter is gradual, slightly easier to meter out the product relative to whenever our next pump-out might be...

-Chris

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We are very fortunately to have the developer of both K.O and NoFlex as TF members.

Replace the hoses between the holding tank and the overboard through hull with high quality hose material.