Somebody has said there is a smell like fish oil coming from her hot press (not sure if the term 'hot press' is used worldwide: the airing cupboard / the cupboard with the hot water tank in).

Her house doesn't have mains gas.

She's checked for anything visible that it could be -- no fish oil tablets in pockets of clothes; nothing like that.

What might this be?

And how might this be dealt with?

(Firstly, I want to check that it's not likely to be some kind of poisonous gas or something. And secondly whatever it is, to try and sort it, to improve the space -- so she can use the cupboard.)

  • Make sure there isn't a dead animal like a dead mouse or lizard trapped under something.
    – PJS1987
    Jul 29, 2017 at 22:38

3 Answers 3


by fish oil smell, do you mean a smell of sulfur? if so, it could be that the pressure relief valve is opening or the tank is leaking in some manner, and the heated water is releasing a sulfurous odor. look for any signs of leaking water.

a common place for a water heater to leak is the pressure relief valve. if the relief valve is leaking or opening, check the water pressure and the thermostat. high water pressure can force open the relief valve and a thermostat set too high or malfunctioning can cause over pressure. if there is a one-way valve near the inlet side of the water heater, that could prevent the water from expanding back and forcing water out the pressure relief valve.


In order to answer your question, you will need to post more information.

The following information is needed:

  • a link to her municipality's water quality report (has info such as pH, hardness, etc.; if the report does not include pH, you/she will have to test the pH of the incoming cold water)
  • the temperature of the water in the water heater (looking at a dial with a sticker on it is not sufficient; you need a thermometer of some sort -- run the hot water from a tap fed by the water heater until hot water starts coming out, run it for 30 more seconds, then fill up a glass and take the temperature with a thermometer); if the temperature is too low, bacteria will form in the water heater
  • the age of the water heater
  • a picture of the water heater
  • a picture of the top of the water heater, specifically the hex bolt head of the anode rod (some anode rods create sulfur smell if they are incompatible with the water's chemistry, namely the pH)

I had a similar smell from my hot-press, upon investigation it turned out to be the insulation around the wires inside of the power switch (flick-switch) burning. The wires were not suited to dealing with the high voltage and the melted against one another, which turned out to be quite dangerous!!.........dont know if this will help but it would be worth a check.

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