My water storage heater keeps pouring cold water out through the pressure and temperature relief valve!

Has this always happened or did it just start recently?
Have you installed a new pump or replaced the pump pressure switch recently?

Check the pressure being created by the pump is not higher than the setting of the pressure release valve. A standard C-Warm unit is supplied with a 2.5bar (35psi) rated valve, the maximum recommended pressure from the pump is 2.1bar (30psi), this allows for some expansion in the system.

If the pump pressure is too high the correct solution is to change your pressure switch for one with a lower setting. Do Not replace the relief valve with a higher pressure unit, this may be incompatable with the heater and cause it to split or explode.

The hot water from my water storage heater is so hot I am worried it may injure someone. How can I control or reduce the temperature?

If this occurs when using an immersion heater adjust the setting on the thermostat so it cuts off at a lower temperature.

If this occurs when using the engine we recommend fitting a 'Cylinder Thermostat' or a 'Blender Valve', see 'C-Warm Heater Accessories'.
A 'Cylinder Thermostat' is a valve (like a radiator valve) which locates in the feed line to the heater coil with a sensor fixed to the  heater. When the temperature reaches the setting on the valve the line is shut so the water gets no hotter.
A 'Blender Valve' is a valve which is fitted into the hot outlet line of the heater (with a cold feed connected to it). The required water temperature is set on the valve, the valve then blends cold water with the hot to ensure this temperature is not exceeded.