I am thinking of placing a 1000L rainwater tank in greenhouse to prevent temperatures inside greenhouse from dropping below 0°C(32°F). The tank is from PE-HD plastic. I am not able to assess how likely it is that the frezzing water damages the tank. Does anyone have any experience with water freezing in rainfall tanks? Does it damage the tank even if you fill only 3/4 of it?
It will tolerate a "little" ice; I think one inch thickness would not be bad. It does not need to freeze solid to break . Once a solid layer forms at the surface and is well attached to the sides, continued freezing expansion will pressurize the water until the tank bursts. Freeze damage of equipment is often NOT where the ice is , but caused by water pressure. The simple solution is an immersion electric heater with a set temperature of about 35 F. Insulation such as Styrofoam panels would also be giant help.