Why does the water from my sea-water intake smell?

Skipper December 30, 2004 Ask The Skipper

Jeffrey Simons asked:

When I flush my head for the first time each day, there is a smell of hydrogen sulfide, which goes away after pumping for about a minute. There is no smell from the holding tank.

This particular odor is somewhat unusual, so I did a little investigation and this is what I found:

Answer:
For your convenience, I’ve highlighted the hyperlinks. Click on the hyperlink to get more information about the selected product.

Source of Smell:
Hydrogen sulfide is not merely a smelly nuisance from stink bombs or rotten eggs. It is a highly toxic gas, which interferes with cellular respiration just like carbon monoxide and hydrogen cyanide. It is not simply a byproduct of some chemical processes but it can arise from some other sources i.e.; decomposition of organic matter such as sewage which in some instances has generated highly toxic, even fatal poisonings.

Health Effects:
Hydrogen Sulfide is a potent chemical asphyxiant, combining with hemoglobin and cytochromes, rapidly stopping oxygen from access to cellular metabolism (just like gases such as carbon monoxide and hydrogen cyanide). Indeed H2S is arguably as toxic as Hydrogen Cyanide HCN.

Although Hydrogen Sulfide is very foul smelling, it also quickly paralyses ones sense of smell. It can go on to overcome the victim and eventually cause death. Therefore smell cannot be relied upon to provide warnings of this treacherous gas. Hydrogen Sulfide is also an irritant of mucous membranes, eyes and the respiratory tract.

You have a potentially serious problem that should be looked after immediately. First of all, avoid breathing this gas. Make sure that you have positive ventilation in the head area to reduce the build up of gasses that could overcome an unsuspecting visitor, that may think that they are just dealing with a smelly toilet. Until you resolve the problem, add one ounce of Aurora Odor Free toilet chemical to the bowl when leaving your boat. It will help to neutralize the bacterial action in the bowl and reduce the build up of stagnate gas.

The source of you problem is either something lodged in your water intake, that is decomposing, or the water where you are mooring your boat may be contaminated. The water in your toilet bowl and in the intake hose apparently contains organic matter such as sewage that is decomposing and giving off the gas. You should take a sample of water from around your boat and have it checked. It that is not the problem then you should check your intake hose for the contaminate source and remove it.

A last resort is to re-plumb your toilet to flush with fresh water from your water tank rather than using seawater.

Thanks for your question,

Captain Aurora