Water smells like onions...

[Schmill]

Ok, this is a very strange one, and I don't really know what to do about it

Occasionally, when running a bath or shower the water has a distinctive oniony smell to it, (I've not noticed it anywhere other than in the bathroom, but that could be because I don't spend as long 'with the water' in other rooms! The bathroom was refitted in the last year with some runs of new copper pipes etc, but the water doesn't 'smell' coppery.
I've checked the cold water tank in the loft and it all looks clean and clear.
Hot water comes via an indirect open-vented cylinder (if that makes any difference).

Anyideas at all on this, or where I should start to look?

Thanks

 

[Charnwood]

'Oniony' smell can be caused by damp.
I always know our shower curtain is past the need for a wash when I smell onions.

 

[Schmill]

lol - Never thought it could be "not the water but something effected by the water" !
I think our curtain was washed recently, but I'll bear it in mind for the next time I smell it