continuously getting air in system

[DP]

Holty, water will not compress. When pump switches on, and it starts pulling water, if there indeed is a dip in water level (yet to be verifyed by OP as described in my earlier post), can you suggest what component is acting as expansion chamber that is allowing water level to drop in the combined feed and vent to level that allows air to be picked up by the pump? I can envisage slight dip in water level when pump kicks in but a fall in water level to allow air ingress is difficult to picture.

Do not understand what you mean by cold feed being too near the water level. The tee that commons vent and feed is approximately 20 inches below the water level. Checking the gate valve (I would strongly recomend it be removed) is a valid point. If it were closed or blocked, water level in the combined feed and vent could well be below the tee pump is connected to.

 

[bengasman]

.. older pumps werent as effective as they are now...

I always thought any new 0.5 bar pump has pretty much the same characteristics as any other new 0.5 bar pump as long as they run at top speed.

 

[Nige F]

.. older pumps werent as effective as they are now...

I always thought any new 0.5 bar pump has pretty much the same characteristics as any other new 0.5 bar pump as long as they run at top speed.

SMC commander ...wonderful piece of equiptment

 

[picasso]

I reckon if the f&e water level is set very low,the new pump will drag air in as it starts, there isint enough static head anyway, I,ll get me coat

 

[Sandy43]

I am not heating engineer or a plumber but i do look into this forum often.

May I suggest that if the pump is quite powerful and does suck a lot but the water in the F&E may not be enough and it empties fast enough.
As the F&E tank may not filling that fast and air could be sucked in.

Could the water level in F&E is increased slightly more and than try so
that F&E tank offer more water than the pump can suck

 

[holty]

a pump can still draw air in a system by a vortex.if that still confuses. i give up.