Water Heater Leaking from back of heater

[MCGROWNHS]

Hi we have an Ariston new europrisma 10 UR 3KW heater and it has started to leak from a hole that is covered with tape at the back of the heater. I have tried to find something that explains what this hole is but can't find anything. The heater has been in about 3-4 years and only started leaking yesterday. Any help would be greatly appreciated. Had another look - looks like water is coming from under the heater and the water coming from the heater is yellow!!!

 

[SimonG]

Is it a pressure relief device?

Have a look online for user manual.

 

[MCGROWNHS]

Is it a pressure relief device?

Have a look online for user manual.

Hi Simon
I have looked at the manual and it doesn't help unfortunately. The leak is definitely from the bottom and the water has a yellow tinge to it. think we need a new one!