Hi everyone. My truman boiler is dumping my hot water every time I open my hot taps. The red button is in the closed position on the safety valve. When we turn the taps on the button stays up in the closed position but the hot water pours out the valve underneath the van. I realise the weather is cold at the moment but the heating is on in the van, the safety valve is next to the boiler and is warm. Any ideas?