The ideal pressure for a boiler is around 12 psi (pounds per square inch) . Most boilers have a pressure gauge that displays different-colored zones, with the green zone indicating the optimal pressure range. The usual cold pressure of a boiler should sit at about 12 psi, but pressure changes of a few psi one way or the other can be brought about by atmospheric conditions. When the unit fires up the heat, the pressure should rise to about 20 psi while its heating element operates, which is still in the normal pressure range. If you live in a multi-story home, the pressure range may be slightly higher, such as 15 psi for two floors or 18 psi for three. However, its important to consult the manual that came with your boiler to find the optimal pressures, as there may be exceptions to the generally accepted pressure ranges. If youre experiencing issues with your boiler pressure, such as not receiving any hot water or heating, or the radiators in your home not heating up correctly, its important to take action to keep your system in optimal condition.