Shock the Hot Water Tank

[Howler]

Hi, There’s that that sickly sweet/sour smell coming out of the faucets, but only for hot water. I shocked the main fresh water tanks and the cold water is fine. Not sure of the best way to isolate the hot water tank and shock only that.

I’m thinking of disconnecting the cold water inlet hose and pumping bleach water in, then using the winter drain valve to empty it followed by multiple rinses using the same method.

Is that the right method? Alternative suggestions?

Thanks!

[b_ohare]

You probably want to check (and likely replace) your water heater pencil anode every year (this picture is corrosion of the heating element after 2 years without replacement). It might be your anode is completely worn down.

You'll also likely need a long-grip adjustable slip lock nut wrench (the nut I had to remove is 2 1/8" but you can't even get a spanner/adjustable wrench in there because it's too tight): https://amzn.to/3LKbxyi . And as your hot water already smells, you'll also need https://amzn.to/3lCVp7e and elbow grease

[peghall]

If there is an anode. The least expensive marine water heaters have anodized steel or aluminum tanks, no replaceable anode(s). The rotten egg smell in only the hot water begins to occur as the anodizing wears off. The only cure: a new water heater.


--Peggie

[Howler]

Originally Posted by peghall

If there is an anode. The least expensive marine water heaters have anodized steel or aluminum tanks, no replaceable anode(s). The rotten egg smell in only the hot water begins to occur as the anodizing wears off. The only cure: a new water heater.


--Peggie

Hi Peggie, The water heater is only in its 5th season. Could the anodizing already be wearing off that soon? Thanks.

[GordMay]

What Peggie & b_ohare said.

The most common odor problem, from water heaters, is a rotten egg smell, that comes out of your faucets and fixtures, when running hot water. This smell is typically caused by sulfate-reducing bacteria, that can develop within the tank. They feed on sulfur, and produce hydrogen sulfide gas, as waste.

This issue usually happens when warm water is left too long in the tank, and bacteria builds up in the water. This problem can also happen if you have R/O water, and are not treating the water with chlorine, or your municipal [shore] water is supplied from the far end of the water main [low chlorine residuals].

Despite the wretched smell, hydrogen sulfide is NOT a health risk.

A less common problem, that causes a sulfur odor, is when you have a water softener, and a magnesium anode rod, inside the water heater. The soft water breaks down the magnesium, and creates sulfate gas within the water heater. Typically, if you have this problem you will have water and air coming out of your faucets, and a sulfate smell to the water.

Softening can also speed up anode consumption, by increasing the conductivity of the water. That can increase the amount of hydrogen sulfide gas produced.

Aluminum anode rods are cheaper, and tend to last longer than magnesium rods, although they come with their own set of problems, since they deteriorate faster, and can therefore contribute to sediment build-up in your tank, and plumbing pipes.
Fortunately, there are other cutting-edge anode rod options [aluminum/zinc alloy, and even powered anodes] on the market, that may prevent your heater tank from releasing this rotten egg smell, and/or rusting faster.

If you’re planning on being away from the boat for some time you should, at a bare minimum, turn off the power to your water heater. Cold water can sit in the tank, without building much bacteria. Better yet, drain the tank.

[Howler]

Thanks for the replies. I should point out that the smell isn't sulfur / rotten eggs. It's more of a sweet/sour kind of smell.

[rslifkin]

Typically when bleach shocking the rest of the system I drain and re-fill the water heater (with it turned off) so it gets bleached, then flush it after. That's the easiest way I can think of.

[tamicatana]

Do you use the winterizing antifreeze in your system? IIRC that has that sickly smell

[Howler]

Originally Posted by tamicatana

Do you use the winterizing antifreeze in your system? IIRC that has that sickly smell

Not the hot water boiler. I disconnect it and drain it for the winter.

[Rumrace]

Yup every water heater I attempted to fix got replaced. My boat sat on the hard for awhile before I found it. I treated the fuel and the water system with CLR. If anything is corroded the CLR sure ends the part.
The only damage was 3 facects the shower bilge pump and the shower. All from winter storage freezing two winters.
The water antifreeze is red here and sweet but not toxic. Takes for ever to flush it out.
I 3D printed a European thread water fill neck so I don’t stand around with a cut hose in a hole for 1/2 hour.

[Rumrace]

Reads like I used CLR on the fuel. I DIDNT!
was 3 water filters with ceramic and micron filters a pump. Came up real clean.

[GordMay]

Originally Posted by Howler

... the smell isn't sulfur / rotten eggs. It's more of a sweet/sour kind of smell.

How else would you characterize the odour?
Sweet & sour seem to be opposites, to me.

[Rumrace]

The European water fill is now public domaine on line. It’s listed as Beneteau Water Fill . Thinginverse.com
I printed a white one in ASA and gave it to a Hanse owner to test. So far Dufour Jeanneau Beneteau Hanse all fit this thread. I added 1% to the file because I was using ASA which shrinks 1%. ASA in bright colours are hard to get so I’m just using white.
I’m going to make another one for domestic boat threads. The domestic quick release hoses snap on and the 4 vents assure no over pressure.

[sailcrazy]

following. I replaced our water heater back in 2003, and have had no issues/paid no attention to it since! It is a 11gal Force 10, with both an electric and eng water loop for heating-I guess I'd better look to see if there's a replaceable anode. We typically leave our boat on the hard each season, for 4-6 months, but she's never seen freezing wx. We just fill the water tanks, run fresh water thru the system and ea faucet, and then leave her on the hard. I guess we've just been lucky.

[toddster8]

Originally Posted by GordMay

How else would you characterize the odour?
Sweet & sour seem to be opposites, to me.

That's kinda sorta how some people describe sulfur dioxide gas (there is no such thing as "sulfate gas.") It's what you get when you "pickle" things, like a watermaker with bisulfite. Perhaps what you were trying to describe in the long post above.

Both hydrogen sulfide and sulfur dioxide gas are harmful with high concentrations or chronic exposure, but fortunately the odor-threshold is extremely low, so it's easy to avoid.

FWIW, I just shock chlorinated my home well, and it took a lot longer to get the stuff out of the hot water circuit than cold. Not as much flow through that side of the system as one might think, even with all the mod cons running.

(Plus, of course, gases and organic acids are less soluble in hot water, so you're just more likely to smell them there.)