Heads inlet pipe smell

[Hydrozoan]

^^ Perhaps my point was a too fine. … A lot of variables, to be sure.

I understand what you are now saying, but had in mind your observation “Actually, no biological matter is required” at #68, which I thought a potential cause of confusion.

I’m sure you are right that organic matter on hose walls might provide an adequate food source for hydrogen sulfide production. But so may organic matter from land run-off or from in-situ marine production (which are likely often to produce much higher levels of both dissolved and particulate organic matter than in your marina tap water, for example) so that cross-contamination with the heads discharge side is not necessarily a precondition for hydrogen sulfide production, even were there to be no great build-up of organics on the intake hose.

 

[thinwater]

I understand what you are now saying, but had in mind your observation “Actually, no biological matter is required” at #68, which I thought a potential cause of confusion.

I’m sure you are right that organic matter on hose walls might provide an adequate food source for hydrogen sulfide production. But so may organic matter from land run-off or from in-situ marine production (which are likely often to produce much higher levels of both dissolved and particulate organic matter than in your marina tap water, for example) so that cross-contamination with the heads discharge side is not necessarily a precondition for hydrogen sulfide production, even were there to be no great build-up of organics on the intake hose.

No, not food source. Bacterial culture home. Bear in mind that it only takes a few ppm H2S for it to be noticeable. The required amount of sulfur, whatever the source, is really tiny. What matters is how long the hose remains anoxic. This is why when cruising it goes away very quickly.

 

[Hydrozoan]

No, not food source. Bacterial culture home. ….

For a period of time, anaerobic sulphate-reducing bacteria can survive without an external organic carbon food source, using the sulphate to oxidize organics already synthesized within their cells. But they require such a source for their long-term survival, growth and reproduction. That’s all I’m saying – but perhaps it’s so simple and obvious that I’m causing confusion, in which case my apologies!

 

[thinwater]

For a period of time, anaerobic sulphate-reducing bacteria can survive without an external organic carbon food source, using the sulphate to oxidize organics already synthesized within their cells. But they require such a source for their long-term survival, growth and reproduction. That’s all I’m saying – but perhaps it’s so simple and obvious that I’m causing confusion, in which case my apologies!

Yup, we're splitting hairs! I was simply trying to inform readers that the primary source of sulfur is generally the water, not biomass. And that seawater is high in sulfate, just as it is high in NaCl.

Good conversation.

 

[Hydrozoan]

Good.

In relation to Vyv Cox’s bottle experiments, he says on his site ‘I conclude from this research that hydrogen sulphide in sea toilets does not occur by degradation of seawater. It seems far more likely to be due to contamination by human waste. The second part of my investigation looked at this.’

I could not see ‘the second part’, so my apologies to Vyv if what follows is covered somewhere else.

I think that there was probably an insufficiently large anaerobic bacterial ‘seed’ population and/or insufficient organic ‘foodstuff’ in the water he used to result in any observable hydrogen sulfide production, at least over the periods involved. So the absence of hydrogen sulfide in that case does not prove that when it is formed in a heads, the sulfur comes from the waste rather than from the seawater.

However, in practice I suspect that if significant waste cross-contamination is occurring, there is likely to be enough sulfur/sulfate from either the seawater or the waste to generate sufficient H2S to cause a smell! But my point is that waste cross-contamination is not a necessary component, if there is sufficient natural organic matter available from other sources, together with an anaerobic bacterial seed and seawater sulphate.

 

[john_morris_uk]

Putting anything in the toilet bowl will do nothing to help. The smell is just natural breakdown of (probably polluted) seawater in the inlet pipe. It goes as soon as the toilet is first flushed after a day or so of not being used. About the only solution is fresh water flushing, but most boats don't have enough spare water for that. I've noticed that the intensity of the smell varies by location, according to seawater quality.

Your suggestion would appear to make sense but has proved to be wrong.

There were some experiments done with sea water a little while ago.

Sealed up and even encouraged to decompose, none of the samples produced the smell.

It's waste matter leaking back past the pump into the 'inlet' or being recycled via the sea water outside the hull (as others have pointed out...)

Edit: I see that others have pointed out Mr Cox's experiments.

 

[Hydrozoan]

Your suggestion would appear to make sense but has proved to be wrong.

There were some experiments done with sea water a little while ago.

Sealed up and even encouraged to decompose, none of the samples produced the smell.

It's waste matter leaking back past the pump into the 'inlet' or being recycled via the sea water outside the hull (as others have pointed out...)

Edit: I see that others have pointed out Mr Cox's experiments.

I beg to disagree, making the same proviso that I did above - namely that I could not see the ‘second’ part of Vyv Cox’s investigation to which his site refers. https://coxengineering.sharepoint.com/Pages/Toilets.aspx

I do not think that his bottle experiment could test the hypothesis that waste matter leakage/recycling was the only possible cause of H2S formation in heads – and indeed, his intention in carrying it out was rather to test his view: ‘That seawater, or the organisms within it, can break down sufficiently to produce serious hydrogen sulphide (H2S) smells seemed to me to be unlikely.’

But it seems that his seawater samples were relatively ‘clean’ (‘The seawater source in each case was the South Ionian Sea, well away from land’) - i.e. they were likely to be low in total and dissolved organic carbon, TOC/DOC. As a result:

(1) They quite possibly did not become anoxic anyway – i.e. there may well have been enough oxygen present at the start to cope with the amount of aerobic action taking place on the likely low DOC/TOC, without becoming totally depleted. (Without oxygen measurement one could not tell, unless hydrogen sulfide were obviously present – which it proved not to be, by smell.)

(2) Even if anoxic conditions had been achieved, there may not have been enough TOC/DOC remaining, or a sufficient ‘seed’ of anerobic sulfate-reducing bacteria present to bring about H2S production in the time available.

For H2S to be formed, (i) anoxic conditions need to be achieved by depletion of oxygen (through aerobic degradation without oxygen replenishment), under which (ii) anaerobic, sulphate-reducing bacteria can grow, provided also that (iii) an organic carbon ‘food’ source is available for them (the oxidation of which they achieve using sulphate instead of oxygen, in which process hydrogen sulphide is formed).

It is my view that, whilst heads waste leakage/recycling may be a cause, it is entirely possible that natural, non-faecal organic carbon can also provide their organic carbon ‘food’ source. That is the more likely in coastal waters (high organic carbon from land run-off) and at times of high marine primary production (high levels of phytoplankton and their exudates and decay products).

So I broadly concur with pvb, though not in excluding the possibility of waste leakage/recycling, nor in his reference to ‘probably polluted’ seawater. Having said that, pollution by nutrients (eutrophication) could of course be one cause of elevated levels of phytoplankton.

PS Vyv himself noted above that ‘I did the work in Greece, where maybe the chemical constituents differ from UK. Could maybe justify being done again in home waters.’ I’m suggesting that his bottle experiment would be more likely to produce H2S if repeated with, say, a UK coastal or estuarine seawater sampled at the time of the spring phytoplankton bloom.

The potentially important difference would not be in the sulfate level (plenty of that in any seawater of reasonable salinity) but in the TOC/DOC, which being putatively much higher would be more likely to (a) bring about anoxic conditions and (b) provide the organic food source for the anaerobic, sulphate-reducing bacteria. Of course I’m not saying it would definitely produce discernible H2S, but that I would not be especially surprised if it did – just as I was not especially surprised that his (likely?) low TOC/DOC Ionian samples didn’t.

 

[john_morris_uk]

Point taken, and I'm not a bio chemist so I bow to your knowledge.

However it doesn't explain the fact that if I really flush the toilets on our boat well. (And I mean thirty or more pumps) before I leave the boat I get no pong on return. The multi flush would clear out all debris and only leave sea water in the inlet pipe. To my limited logic, it would appear a lesser flush might leave faecal and other matter leaked back (or pumped back in via the sea) in the inlet.

 

[KellysEye]

The first thing to do is take the pipe off and smash it on the side of the pontoon or similar. This will remove the calcium build up and usually the smell. If there is still a smell remove the joker valve and get the calcium off that or fit a new one.

 

[Hydrozoan]

Point taken, and I'm not a bio chemist so I bow to your knowledge.

However it doesn't explain the fact that if I really flush the toilets on our boat well. (And I mean thirty or more pumps) before I leave the boat I get no pong on return. The multi flush would clear out all debris and only leave sea water in the inlet pipe. To my limited logic, it would appear a lesser flush might leave faecal and other matter leaked back (or pumped back in via the sea) in the inlet.

Thanks. I am not a biochemist either, and would welcome the thoughts of one - or those of a marine microbiologist. My view does depend in part upon my surmise (not I hope an unreasonable one) about the likely low TOC/DOC of Vyv’s bottle experiment samples. I hope he may be able to say something about that. Regarding your second paragraph, your logic seems impeccable. If heads waste gets to the inlet by either mechanism, I don’t doubt it could be the cause – and said so in the penultimate paragraph of the main post, before the PS.

All I say is that if the seawater pumped in very thoroughly were to contain a high level of TOC/DOC from other sources (e.g. from a high level of phytoplankton during the spring bloom, or as a result of eutrophication) the latter could perhaps be the carbon source. That is what I believe pvb was saying, and I don’t think Vyv’s experiment firmly disproves that possibility as your reply to pvb suggested.

But perhaps the TOC/DOC from a bloom or period of eutrophication might not reach a high enough level for that suggested mechanism. Had I better access to the literature and the oomph of youth, I might look for data on the Biochemical Oxygen Demand (BOD) of temperate estuary samples during the spring bloom or a eutrophication episode.

Anyway, more than enough from me – a very interesting subject, but as thinwater said ‘A lot of variables, to be sure.’

 

[RichardS]

The first thing to do is take the pipe off and smash it on the side of the pontoon or similar. This will remove the calcium build up and usually the smell. If there is still a smell remove the joker valve and get the calcium off that or fit a new one.

That doesn't seem logical to me. The build up of calcium can only be on the outlet pipe so how can that smell back in the bowl when you first flush it as the smell is being "flushed" in the opposite direction.

Richard

 

[john_morris_uk]

That doesn't seem logical to me. The build up of calcium can only be on the outlet pipe so how can that smell back in the bowl when you first flush it as the smell is being "flushed" in the opposite direction.

Richard

I thought that too.

There's something going very wrong if there's calcium build up in the inlet.

 

[ex-Gladys]

I thought that too.

There's something going very wrong if there's calcium build up in the inlet.

Sea water has a naturally very high calcium content as I understand it..

 

[john_morris_uk]

Sea water has a naturally very high calcium content as I understand it..

Precipitated out and deposited when mixed with urine.

Not in the inlet pipe then...

 

[nigelmercier]

That doesn't seem logical to me. ...

Perhaps someone who hasn't read the thread and is thinking outlet pipes.

 

[vyv_cox]

Good.

In relation to Vyv Cox’s bottle experiments, he says on his site ‘I conclude from this research that hydrogen sulphide in sea toilets does not occur by degradation of seawater. It seems far more likely to be due to contamination by human waste. The second part of my investigation looked at this.’

I could not see ‘the second part’, so my apologies to Vyv if what follows is covered somewhere else.

I think that there was probably an insufficiently large anaerobic bacterial ‘seed’ population and/or insufficient organic ‘foodstuff’ in the water he used to result in any observable hydrogen sulfide production, at least over the periods involved. So the absence of hydrogen sulfide in that case does not prove that when it is formed in a heads, the sulfur comes from the waste rather than from the seawater.

However, in practice I suspect that if significant waste cross-contamination is occurring, there is likely to be enough sulfur/sulfate from either the seawater or the waste to generate sufficient H2S to cause a smell! But my point is that waste cross-contamination is not a necessary component, if there is sufficient natural organic matter available from other sources, together with an anaerobic bacterial seed and seawater sulphate.

Sorry, the second part was never completed. I believe that the main contributor to inlet pipe smell is the poor quality of the rubber flap valves, which at best seal imperfectly and at worst badly. Coupled with the simple piston ring, a single O-ring, there is inevitably some transfer of faecal matter into the inlet pipe. Toilets without such valves, e.g Lavac and Jabsco lite, seem to be far less afflicted by H2S smells. When they are the cause seems to be recirculation via the sea.

Edit: apologies to John Morris, who I see said almost exactly the same a page ago!

 

[Hydrozoan]

Sorry, the second part was never completed. I believe that the main contributor to inlet pipe smell is the poor quality of the rubber flap valves, which at best seal imperfectly and at worst badly. Coupled with the simple piston ring, a single O-ring, there is inevitably some transfer of faecal matter into the inlet pipe. Toilets without such valves, e.g Lavac and Jabsco lite, seem to be far less afflicted by H2S smells. When they are the cause seems to be recirculation via the sea.

Edit: apologies to John Morris, who I see said almost exactly the same a page ago!

Thanks Vyv. I was a bit concerned that I might have missed the second part.

With regard to your bottle experiments, you will have noted my suggestion that the TOC/DOC of your Ionian seawater may have been low – IIRC you said you took the water well offshore. Do you think that it might perhaps have been too low to bring about anoxic conditions favourable to anaerobic sulphate-reducing bacteria, or to provide an organic food source for their activity? And in particular, do you think that the TOC/DOC might have been a lot lower than would be expected in a UK coastal water bloom, or in waters subject to eutrophication? (It looks beautifully transparent in the clear bottles in your photograph, but my perception may be skewed by being used to the UK East coast! )

As you will have seen, I noted your idea above (at #78) that the experiment might usefully be repeated with UK water, and suggested that using a high TOC/DOC water during a spring bloom or a period of eutrophication might be the most informative.

As I said in response to JM, I don’t doubt that waste cross-contamination may be a cause of H2S production: I just wonder if high ‘natural’ TOC/DOC may also sometimes be the organic load which brings about anoxia, and then provides the food source for sulphate-reducing bacteria in the heads inlet. (By ‘natural’ here I mean not derived locally from waste leakage/recycling; I do not exclude organics resulting from more distant pollution, eutrophication etc.)

Thanks again – and in anticipation.

 

[PaulRainbow]

Toilets without such valves, e.g Lavac and Jabsco lite, seem to be far less afflicted by H2S smells. When they are the cause seems to be recirculation via the sea.

My current boat came with a Lavac. Until this thread i'd forgotten about the smells we used to get with Jabsco toilets. Although, our Jabsco's were electric macerator units, still smelt though.

 

[Ric]

Sorry, the second part was never completed. I believe that the main contributor to inlet pipe smell is the poor quality of the rubber flap valves, which at best seal imperfectly and at worst badly. Coupled with the simple piston ring, a single O-ring, there is inevitably some transfer of faecal matter into the inlet pipe. Toilets without such valves, e.g Lavac and Jabsco lite, seem to be far less afflicted by H2S smells. When they are the cause seems to be recirculation via the sea.

Edit: apologies to John Morris, who I see said almost exactly the same a page ago!

I see a lot of boats with water maker inlet teed to toilet inlet!

 

[vyv_cox]

Thanks Vyv. I was a bit concerned that I might have missed the second part.

With regard to your bottle experiments, you will have noted my suggestion that the TOC/DOC of your Ionian seawater may have been low – IIRC you said you took the water well offshore. Do you think that it might perhaps have been too low to bring about anoxic conditions favourable to anaerobic sulphate-reducing bacteria, or to provide an organic food source for their activity? And in particular, do you think that the TOC/DOC might have been a lot lower than would be expected in a UK coastal water bloom, or in waters subject to eutrophication? (It looks beautifully transparent in the clear bottles in your photograph, but my perception may be skewed by being used to the UK East coast! )

As you will have seen, I noted your idea above (at #78) that the experiment might usefully be repeated with UK water, and suggested that using a high TOC/DOC water during a spring bloom or a period of eutrophication might be the most informative.

As I said in response to JM, I don’t doubt that waste cross-contamination may be a cause of H2S production: I just wonder if high ‘natural’ TOC/DOC may also sometimes be the organic load which brings about anoxia, and then provides the food source for sulphate-reducing bacteria in the heads inlet. (By ‘natural’ here I mean not derived locally from waste leakage/recycling; I do not exclude organics resulting from more distant pollution, eutrophication etc.)

Thanks again – and in anticipation.

Definitely worth repeating in different waters but my home in winter is Menai Strait, allegedly some of the cleanest water in UK. These days it seems quite difficult to find pollution in UK(!) but your suggestion of spring bloom somewhere with a little less natural flow is a good one. Are you volunteering?