Thans for your help in adavance,

I have a hot water heating system boiler with a red pump at the side of the boiler. I would like to know does the pump pushes the water through the
System.or pull the water back to the boiler.:rolleyes:

Pumps do a much better job of pushing than sucking. The least little leak on the suction side of a pump draws air in and keeps the pump from pumping water. Therefore, the pump pushes water from the boiler through the system and back.

Thank you for your reply.
I have add a new zone for the attic with a one way thermostat controlled valve.but I find the water rise via the assumed return line.
I have then asked many people the same question that I pose to you and the reply was 50... 50.
I do concur with your theory,for that reason I have installed the way I did.

Thanks
Karen

Thans for your help in adavance,

I have a hot water heating system boiler with a red pump at the side of the boiler. I would like to know does the pump pushes the water through the
System.or pull the water back to the boiler.:rolleyes:

It is not a pump, it is a circulator. It only works in a closed , full system and moves the water in the direction of the arrow. Air in the system comstitutes a blockage ( just like you put a cork in the pipe ) And has to be purged out .