Boiler water heater had it!

Hi Guys,
I'm not sure anyone will be able to help me with this but I have a Cascade water heater (for the shower). Excuse me if I get the lingo wrong, I have no idea what I am talking about. The boiler part (Large round metal cylinder) seems to have burst and there is water pouring out the bottom right hand corner. Do I need to have the whole thing replaced or am I able to maybe seal this with some silver solder. Suggestions on what to do would be most helpful. Can't even use our sink because as soon as the water pump gets turned out the water starts pouring out the boiler!

Is it a leak or a proper dump valve for frost protection

If it's a dump valve all you need to do when the temperature rises is push the button and it automatically closes. If the outside temp is still below 4 I think it won't close. What kind of vN do you have?

Yeah when the boiler dumps the water the valve needs to be closed otherwise the water you are putting into the tank will run out and the boiler needs to be refilled with water before you switch on the heating. Also make sure you take all the air out of the system. Hope this helps. That's how it works on my van.m

Hi Guys,
Sorry we have been on the road. Thanks for your suggestions, on further inspection/photo action I have shown the problem below. The first picture is taken from the top and the second from the side which shows the problematic area.




I am really sorry if I have added the photos incorrectly, it should be the link to take you directly to the photo if copied and pasted into your browser (obviously without the [img] on both ends)

Thanks
Bridget