The cold water is fine, the house next door has the same water and electric hot water heater too, but theirs doesn't smell. We have put bleach in the hot water tank, it hepls for a while then the smell come back.

When is the last time your anode rods were inspected?

https://www.waterconnection.com/the-anode-rod/

It sounds like you are having trouble with your ANODE ROD producing hydrogen sulfide gas (sulpher smell like rotten eggs). Here, your best bet will be to remove the magnesium anode rod in the water heater and install a less reactive zinc or aluminum (or combo. Zn/AL) anode rod in the water heater...should resolve the issue for you!

After changing the anode rod out, hike the temperature up to say 160F or so for a couple hours as that should kill any residual sulpher bacterium. Flush the tank and return the temp. to 120F and you should be all set!

Why hasn't your neighbor had the problem you ask? It could simply be a little more time until they do have the problem, or not...depends on too many factors to say exactly. The fact is that you do have a problem and this should fix it for you.

Questions? Let me know, OK?

Good luck!

Mark

How did you put bleach in the hot water tank?