Can Central Heating circulation pumps be generally mounted pumping downwards?

[Fredxx]

Ye I am aware that there needs a way for air to escape.

In the good old days I thought pumps had to be placed pumping up, or horizontally.

[Radio Man]

Placing the pump where any air / gas in the system wouldn?t rise away from it wouldn?t be a good idea some systems have valves which vent air / gas but not all. Air/gas due to chemical reaction in the system collects in the radiators in most systems and you need to bleed them now and then. Inhibitor reduces this or the corrosion that produces the gas to be more accurate. A flush to remove old inhibitor and general muck is a good idea every few years.

[Robin]

The one in the sealed system here was fitted to pump down without an automatic air vent and did indeed fail. After 30-odd years.

[Roger Hayter]

I had a Firebird boiler with two downward pumping standard pumps and they failed every few years. But then I had a lot of trouble with corrosion, gas and loss of pressure.