We have an Atwood marine water heater in our Oceanis 321. Just recently, the water coming out of it has given off a strong sulfur odor. We have been told that it is the sulfur in the water that is causing the problem but this is hard to believe. The water at the marina comes from the same water system that services our home and we don’t have that problem in our house. Further, there is no odor when we boil water on the boat. Has anyone else had this problem and how did it get resolved?
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Could be the heating element
Which should be replaced. Or just try running the water for a while to see if it cycles through. Often does.
Which should be replaced. Or just try running the water for a while to see if it cycles through. Often does.
How long has the water
been sitting in the boat's lines? The hot water tank probably holds about 5 gallons, so open the faucets and run that water through the system. Could also be time to recommission the fresh water system - check the archives for the procedure.
been sitting in the boat's lines? The hot water tank probably holds about 5 gallons, so open the faucets and run that water through the system. Could also be time to recommission the fresh water system - check the archives for the procedure.
Nope, not the heating element...
If the odor is only in the hot water, it's most likely caused by a failed anode. Anodes are included in the water heater of glass-lined steel tanks to protect the inside of the tank against corrosion from acids in the water, stray electrical currents, etc. Glass lined tanks, when the water heater is being built, are heated up red hot. Then glass powder is sprayed inside the tank and it adheres upon contact. However, it doesn't cover every single crack and crevice inside the tank - it should, but in actual practice, it doesn't. The purpose of the anode is to protect those spots inside the tank that have not been glass-covered from rusting away prematurely. The anode is eaten away, rather than the tank being eaten away. Kind of a backup to the glass lining. The anode is a magnesium rod, about 3/4" in diameter that is attached to the inside of the hot water "out" nipple, via a plastic coupling. It is electrically isolated from the fittings and from the tank. It extends all the way across the inside of the tank, stopping just short of the other side. There is an iron rod in the center of the magnesium that supports it, the iron being stronger than the magnesium. As the magnesium is eaten away and the iron rod exposed, there's a chemical reaction between the water, the iron and the magnesium that causes the "rotten egg" smell. Replacing the anode and flushing out the tank will usually make the foul smell go away. However, if the inner tank is not glass, but aluminum, there is no replaceable anode...the tank itself is anodized aluminum...the anodizing has been eaten off the actual tank wall. In THAT case, there's no way to repair it or cure the odor problem short of replacing the water heater. And while I'm not 100% certain, I THINK Attwood water heaters have aluminum tanks.
If the odor is only in the hot water, it's most likely caused by a failed anode. Anodes are included in the water heater of glass-lined steel tanks to protect the inside of the tank against corrosion from acids in the water, stray electrical currents, etc. Glass lined tanks, when the water heater is being built, are heated up red hot. Then glass powder is sprayed inside the tank and it adheres upon contact. However, it doesn't cover every single crack and crevice inside the tank - it should, but in actual practice, it doesn't. The purpose of the anode is to protect those spots inside the tank that have not been glass-covered from rusting away prematurely. The anode is eaten away, rather than the tank being eaten away. Kind of a backup to the glass lining. The anode is a magnesium rod, about 3/4" in diameter that is attached to the inside of the hot water "out" nipple, via a plastic coupling. It is electrically isolated from the fittings and from the tank. It extends all the way across the inside of the tank, stopping just short of the other side. There is an iron rod in the center of the magnesium that supports it, the iron being stronger than the magnesium. As the magnesium is eaten away and the iron rod exposed, there's a chemical reaction between the water, the iron and the magnesium that causes the "rotten egg" smell. Replacing the anode and flushing out the tank will usually make the foul smell go away. However, if the inner tank is not glass, but aluminum, there is no replaceable anode...the tank itself is anodized aluminum...the anodizing has been eaten off the actual tank wall. In THAT case, there's no way to repair it or cure the odor problem short of replacing the water heater. And while I'm not 100% certain, I THINK Attwood water heaters have aluminum tanks.
A little kitchen sink sulfur chemistry
Sulfur dioxide is a smelly gas with an odor that resembles that of a match when it is lit (the match head has sulfur in it). It is an oxidized compound. Sulfate SO4(2-) is the second most common negative ion (after Cl-) in sea water and is fairly common in fresh water. It has little or no taste but can be slightly reduced to sulfite SO3(2-) which converts to SO2 (H2SO3=H2O+SO2), see above for smell. Hydrogen sulfide, H2S, is a reduced compound and is not in equilibrium with atmospheric oxygen which will convert it rapidly to sulfite or sulfate. But in an enclosed tank with a reduced metal like either zinc or aluminum or especially iron or in the presence of organic matter like rubber, the sulfate can be reduced (usually by sulfate reducing bacteria) to H2S which smells like rotten eggs. If you have a rotten egg smell in your water it probably indicates that fresh water with traces of sulfate is standing in the tank or worse yet in rubber hoses which can be used by bacteria to make H2S. Of course rubber itself has a fairly high sulfur content as it is the cross linking agent used in vulcanizing rubber. Pure rubber smells like candle wax when burned but vulcanized rubber stinks because of the sulfur in it. Try burning a rubber band. Your problem probably stems from stagnancy which allows the dissolved oxygen in the water to be consumed allowing the sulfate reducers to thrive and make the smell. Changing from rubber to plastic hose will help. Flush and flush again. A little bleach in the system will make life very hard on the sulfate reducing bacteria which are anaerobes and will die in the presence of hypochlorite ions from the bleach.
Sulfur dioxide is a smelly gas with an odor that resembles that of a match when it is lit (the match head has sulfur in it). It is an oxidized compound. Sulfate SO4(2-) is the second most common negative ion (after Cl-) in sea water and is fairly common in fresh water. It has little or no taste but can be slightly reduced to sulfite SO3(2-) which converts to SO2 (H2SO3=H2O+SO2), see above for smell. Hydrogen sulfide, H2S, is a reduced compound and is not in equilibrium with atmospheric oxygen which will convert it rapidly to sulfite or sulfate. But in an enclosed tank with a reduced metal like either zinc or aluminum or especially iron or in the presence of organic matter like rubber, the sulfate can be reduced (usually by sulfate reducing bacteria) to H2S which smells like rotten eggs. If you have a rotten egg smell in your water it probably indicates that fresh water with traces of sulfate is standing in the tank or worse yet in rubber hoses which can be used by bacteria to make H2S. Of course rubber itself has a fairly high sulfur content as it is the cross linking agent used in vulcanizing rubber. Pure rubber smells like candle wax when burned but vulcanized rubber stinks because of the sulfur in it. Try burning a rubber band. Your problem probably stems from stagnancy which allows the dissolved oxygen in the water to be consumed allowing the sulfate reducers to thrive and make the smell. Changing from rubber to plastic hose will help. Flush and flush again. A little bleach in the system will make life very hard on the sulfate reducing bacteria which are anaerobes and will die in the presence of hypochlorite ions from the bleach.
A cure
is to get in the habit of using the hot water tap all the time. If water sits in the heater, it'll get "moldy." If, especially when there is no hot water, either from the electrical element or the engine heat transfer, use the hot side faucet and you'll run more water through the heater and keep what's in there fresh. Stu
is to get in the habit of using the hot water tap all the time. If water sits in the heater, it'll get "moldy." If, especially when there is no hot water, either from the electrical element or the engine heat transfer, use the hot side faucet and you'll run more water through the heater and keep what's in there fresh. Stu
Btw...residential water heaters also have anodes
But the anode extends down into the tank from the top, whereas they're attched to the outlet fitting on marine versions. However, for some reason the actual tank in residential applications usually develops a leak...or the thermostat fails (about the same to replace as a whole new water heater)...well before the anode is eaten away...you're lucky to get more than 10 years out of a residential water heater. Otoh, it's not unusual at all for a for marine water heater that has a glass lined tank to last 25+ years.
But the anode extends down into the tank from the top, whereas they're attched to the outlet fitting on marine versions. However, for some reason the actual tank in residential applications usually develops a leak...or the thermostat fails (about the same to replace as a whole new water heater)...well before the anode is eaten away...you're lucky to get more than 10 years out of a residential water heater. Otoh, it's not unusual at all for a for marine water heater that has a glass lined tank to last 25+ years.
Already Been There
I put up an SOS a few weeks ago regarding the same issue and had some great responses. Well, from my hot water galley tap I filled bucket after bucket of hot hydrogen sulfur smelling water. I am sure I shocked a few critters off the back of the boat everytime I launched that hot stinking stuff. After literally emptying out the hot water heater my problem was solved. I let the system recharge for a day and proceeded to run the hot water again to check the odor. The dump cured the problem, but gave some insight to water health onboard. Its a wise practice when your not aboard for over a few weeks to run the hot water to prevent bacterial build up. Sulfur bacteria will thrive in any environment including "hot" so its best to try and disinfect above and beyond what comes from the city tap to the marina. I will add a couple tablespoons of liquid chlorox to my fresh water tank on future fill ups to help control algal buildup. Glad to share the experience. Bob Cat 30
I put up an SOS a few weeks ago regarding the same issue and had some great responses. Well, from my hot water galley tap I filled bucket after bucket of hot hydrogen sulfur smelling water. I am sure I shocked a few critters off the back of the boat everytime I launched that hot stinking stuff. After literally emptying out the hot water heater my problem was solved. I let the system recharge for a day and proceeded to run the hot water again to check the odor. The dump cured the problem, but gave some insight to water health onboard. Its a wise practice when your not aboard for over a few weeks to run the hot water to prevent bacterial build up. Sulfur bacteria will thrive in any environment including "hot" so its best to try and disinfect above and beyond what comes from the city tap to the marina. I will add a couple tablespoons of liquid chlorox to my fresh water tank on future fill ups to help control algal buildup. Glad to share the experience. Bob Cat 30
Don't do that, Bob...
Adding a little bleach to each fill is not a good idea. Not only does it damage the system, but unless you add enough to make your water taste and smell like a laundry, it’s not enough to do any good. Even if it were, any “purifying” properties in chlorine evaporate within 24 hours, leaving behind only the corrosive properties that are damaging to aluminum water tanks (including aluminum hot water tanks) and rubber parts in your water pump. An annual recommissioning of the whole fresh water system according to directions I've posted here at least a dozen times should be all that's needed to keep both hot and cold water tasting and smelling as good as any coming out of a faucet on land. Btw...algae doesn't grow in fresh water systems and water heaters...it needs light. There isn't any in a fresh water system. It's the "critters" that thrive in damp DARK places that make fresh water turn funky.
Adding a little bleach to each fill is not a good idea. Not only does it damage the system, but unless you add enough to make your water taste and smell like a laundry, it’s not enough to do any good. Even if it were, any “purifying” properties in chlorine evaporate within 24 hours, leaving behind only the corrosive properties that are damaging to aluminum water tanks (including aluminum hot water tanks) and rubber parts in your water pump. An annual recommissioning of the whole fresh water system according to directions I've posted here at least a dozen times should be all that's needed to keep both hot and cold water tasting and smelling as good as any coming out of a faucet on land. Btw...algae doesn't grow in fresh water systems and water heaters...it needs light. There isn't any in a fresh water system. It's the "critters" that thrive in damp DARK places that make fresh water turn funky.
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