the bottom two radiators on heating system will not keep heat in them have bought heat to radiators but only lasts for approx 1 hour all others are working do not think air is the problem could it be pump? thank you for any help
Read the information and look at the pictures in the free hot water heating lessons at http://www.hydronic.net
Compare your system with the pictures. When you have enough information to describe how yours differs from the pictures, then someone may help you understand the problem.