Sulfur odor in boat hot water system

[Musetta]

I purchased a Hunter 356 in 2016 and replaced the water heater within the first year because of strong sulfur odor and grey to black color in the hot water. The replacement was a Kuuma 6 gallon heater with an aluminum tank. Now, five years later, I have the same problem -- sulfur odor and, when I drain the tank to flush it, black water. Draining and flushing reduces the odor, but only temporarily. I believe that the aluminum tank is reacting with the water in our marina. I have followed previous postings on this topic and know that Peggy Hall says the permanent solution is a new water heater, ideally with a glass-lined steel tank and an anode to protect the steel. So far, I have not found one that will fit in the space available. I have found one with a stainless steel tank and wonder if anyone has any experience with or recommendations about that as an alternative.

 

[DeniseO30]

If you haven't flushed it (which is more work than draining) in 5 years, you have sediment in the bottom.
When the water gets cold bacteria start growing. When the water gets hot killing the bacteria you start to get the rotten egg smell when the water gets cold again.

home water heaters don't smell because the water is kept hot

5 years, you're probably due for another some people think chlorine will help some people try hydrogen peroxide but it's something you have to live with when it comes to water heaters being turned turned on and turned off, you can replace the anode rod but the work to change the anode rod is equal to changing out the water heater so you have something to think about, doesn't matter what the tank is made of, friends of mine hot water tank is glass line it's in a house that they don't use vacant so far that I know about 2 years, guess what the water smells like? My other boat had a glass lined Raritan water heater we changed it out my present boat which I'm selling I changed out the water heater both had rotten eggs and sediment lots and lots of sediment!
good luck!
Rotten Egg Smell in Water Heaters - How to Troubleshoot

 

[dlochner]

Sulfur smelling hot water is almost always the result of the anode being gone. Find the anode and replace it. Sometimes they are part of the hot water outlet.

 

[Don S/V ILLusion]

1. remove the supply hose to the heater and fill a bucket with tank water to see if it smells. You could heat it if necessary.

Assuming it isn’t the water, it’s obviously the tank or tank anode.

2. Inspect the heater tank anode if it has one.

The above steps will confirm if heater replacement is necessary (likely not).

 

[Musetta]

Replying to Denise030 and Dave, thank you both for your quick responses to my post. I did not install an anode when I replaced the old heater, since opinions on the web about its effectiveness varied. I suspect it is too late to install one now. If I end up replacing the heater with the same one (which Denise's post suggests might be an ok option) I will try it with the anode this time.

 

[Musetta]

1. remove the supply hose to the heater and fill a bucket with tank water to see if it smells. You could heat it if necessary.

Assuming it isn’t the water, it’s obviously the tank or tank anode.

2. Inspect the heater tank anode if it has one.

The above steps will confirm if heater replacement is necessary (likely not).

 

[Musetta]

Thanks Don. There is no anode, and the water is ok. So, I think replacement may be indicaed.

 

[JamesG161]

Sulfur in the local water supply where you last filled your tank, is a possibility.

Suggestion is to drain your system and start over again.
Jim...

 

[Musetta]

Thanks!

 

[JoeWhite]

This due to not used water heater water. Drain about one gallon whenever you are on the boat allowing new water to fill the tank. There is no zinc on marine water heaters.

 

[Stu Jackson]

Drain about one gallon whenever you are on the boat allowing new water to fill the tank.

Why bother draining it Just USE it. Just get in the habit of using the hot faucet all the time even when there's no hot water, keeps it movin'.

 

[Crusty Ol Salt]

Why bother draining it Just USE it. Just get in the habit of using the hot faucet all the time even when there's no hot water, keeps it movin'.

Bingo,

I do not use a lot of fresh water, but I keep the tank full for ballast. The water in the tank has sat stagnant for two (2) months. I know that that treatment from the city water system (mostly chlorine) has of dissipated. I will use it for a fresh water washdown of my bilges and refill my tank.

 

[dlochner]

This due to not used water heater water. Drain about one gallon whenever you are on the boat allowing new water to fill the tank. There is no zinc on marine water heaters.

This is correct, there are no zinc anodes in HW tanks, the sacrificial anodes are magnesium because zinc won't work in freshwater. See for example this anode from Raritan.

Raritan Replacement Water Heater Sacrificial Anode - 1790010

Features: A removable magnesium Anode is integral with the hot water discharge fitting The Anode should be checked at least once a year by removing it from the water heater If the Anode diameter is less than 3/8" (9.5mm), it should be replace

www.defender.com

 

[Tally Ho]

Why bother draining it Just USE it. Just get in the habit of using the hot faucet all the time even when there's no hot water, keeps it movin'.

I think that is the best answer. I know on my O’Day 322, if I am not using the water, it will get skanky after a while, particularly in hot weather. I had 2) 30-gallon tanks. I pulled one out to free up some strange space, and I use the water faster in the remaining tank, so that helps with the skanky water. I also put a splash of bleach in the tank when I fill it. I don’t generally drink the water from the tank, but I do brush my teeth with it.

I usually turn the water heater on (AC) when I get to the boat, and use hot water for any cleaning I am doing. As Stu said, use it!

Greg

 

[Ralph Johnstone]

Why bother draining it Just USE it. Just get in the habit of using the hot faucet all the time even when there's no hot water, keeps it movin'.

Such a unique grasp of the obvious .

 

[dlochner]

Such a unique grasp of the obvious .

It comes with age and experience.

 

[Ralph Johnstone]

It comes with age

Yes, but within limits. Beyond those limits comes senility !