Rusty hot water but the cylinder is copper. Any ideas?

[Emver]

My tenant has complained of slightly yellow/brown tinted hot water from the tap. The cold taps are fine.
The flat has electrically heated water stored in the usual insulated copper cylinder with both daytime and off-peak immersion heater elements. All the pipework is copper. This has been happening for the past 3 days, and running the tap for 5 minutes doesn't clear it. Water from the cold taps is clear, so the supply is not the problem.
Any ideas?

 

[fine tune]

galvanised feed tank in loft/airing cupboard feeding hot water tank rusty inside

 

[Newboy]

usual insulated copper cylinder

Definitely a copper cylinder?

 

[Emver]

Thanks for those two suggestions. I'll check them both.

 

[DP]

I would suspect corned up sediment that sits dormant base of cylinder.
If metal storage cistern is rusted, cold water in bath would be rusty too. Sometimes the sediment gets disturbed here too to result in discoloured water.
Check the cylinder immersion heater is not causing the water to boil ie not cutting out

 

[Hot&Cold]

Best to get a proper plumber to inspect,issue a report and if necessary carry out remedial works.It helps to reduce 'landlord risk' and shows the landlord is acting in a responsible manner.

The tenant could have searched the internet,looking for reasons of discoloured water and hopefully not thinking its the L word

 

[Nige F]

The cold taps are fine.
Water from the cold taps is clear, so the supply is not the problem.

Mains fed to all cold taps ?

 

[JohnD]

drowned pigeon on the loft tank.

Clean it out, sterilise it, fit a tight-fitting plastic lid and an insulating jacket.

Keep the immersion heater in the cylinder on, it will at least pasteurise the water and reduce the bacterial content.

(vom)