What would cause a fish-like smell to come from the shower unit even when it is switched off?

Answer 1

I have that problem too. The smell comes from mildew growing on the sides of the drain pipe above the waterline in the trap. It's rather dirty in there below the drain plug, and you never really clean it. When you turn on the water, it disturbs the mildew and releases bad smells. The water trap in the u-turn under the sink keeps sewer smells out but this is before that. The solution is to grab a bottle of bathroom mildew remover and spray it heavily around the drain plug to saturate all sides of the drain pipe. Try this once every few months to keep your bathroom smelling fresh. Don't forget the shower and bathtub drains aswell, and kitchen disposal too if you have a problem there.