Why does my hot water smell like rotten eggs? (Part 1 of 2)

A hot shower can be a really satisfying way to begin (or end) your day…but not if your hot water smells like rotten eggs.

If you’re having a hot water odor problem, don’t worry – there’s a pretty good chance you can solve it on your own with materials you can buy at your local hardware store.

But before we get to that, it’s important to see if the problem is affecting your cold, water, too: if it is, you have a water supply problem, which could require more an extensive remedy from a professional. For now, let’s stick to tackling an odor problem caused by your water heater.

In this first part of a two-part blog post, we’ll look at why your hot water smells like rotten eggs. In Part 2, we’ll explore what you can do about it.

What causes a rotten egg smell in my hot water?

In untreated form, all water contains some amount of sulfur; if you get your water from a well, that sulfur remains in your water, alongside sulfate-reducing bacteria. Both are harmless to humans – and both are eliminated if you get your water from a municipal water supply.

The problem with sulfate-reducing bacteria is that, when combined with sulfate-containing water and the metal inside your water tank, it will create a series of chemical reactions that will ultimately lead to tank corrosion. Sulfur+ bacteria + a corroding water heater tank = hydrogen sulfide (H2S), which smells like rotten eggs.

Viola! (Didn’t think you’d be getting a chemistry lesson in your HVAC blog, did you?).

Another source of rotten egg stink in your tank is your anode rod, which is designed to “sacrifice itself” so it corrodes instead of your tank. When bacteria eats away at your anode, guess what it makes?

You got it, stinky H2S gas. 

But don’t rush to remove that anode rod…we’ll explain why in Part 2.

What can make the sulfur smell worse?

Two things can make the smell of sulfur in your hot water worse, including:

• Using a water softener – a water softer makes the water in your tank more conductive, which speeds corrosion (and therefore H25 production).
  Static water – If your hot water doesn’t move frequently – say, if you have a seasonal home –  H2S gas will build up.
• By now we have a good idea about how an odor problem develops in your home water supply. The question is, how do you get rid of it? We’ll explore that in Part 2. Stay tuned!

Want a great way to avoid stinky water altogether? Invest in a tankless propane water heater, which heats water on demand (no storage tank needed!). To learn more about other benefits of tankless propane water heaters, contact a specialist at P. Gagnon & Son today!