Automatic air valve old system

[Roger44]

Hi All,

My father has a very old system which I've cleaned and drained. The problem he has is, he keeps having to bleed all the rads every time he uses the heating which is a real pain. Air is being drawn in somewhere but we can't fathom it out. We shall be renewing the system after winter, but as a quick/temporary

fix could I install an automatic air valve after the pump to get rid of the air in the system? Could I just cut off the manual bleed pipe on the very right of the pump and install it on top of that long vertical pipe where the manual bleed was? Any help much appreciated.

 

[ShaunCorbs]

Whose changed the pump ?

 

[Last Plumber]

Why have you got two pumps in tandem ?
Am I looking at the pic wrong?

 

[ShaunCorbs]

Why have you got two pumps in tandem ?
Am I looking at the pic wrong?

Thought it was an old pump plan at first but think someone's changed the pump because the other one is weak

 

[Roger44]

Hi, It's a Myson controller pump it's got 3 postions on the front, I assume it's like a diverter valve and a pump it's decades old but not sure exactly how it works. I fitted the Grundfos pump myself it's not leaking as far as I'm aware, but I suppose it could be drawing air in, but have done it up well with new washers. When I'm up in the attic I can hear the vent pipe that goes up over the top of the expansion tank making a sucking sound/gurgling, is this normal? Would the automatic air vent see me out over winter until I can get the problem properly sorted? Many Thanks.

 

[Roger44]

Hi,

Just a thought..... if the two pumps are running in tandem and both are on speed 3, should I turn them both down to speed 1. Could it draw air in because the flow rate is too fast, due to the fact that the replacement Grundfos pump is much stronger? The old Grundfos pump was basically knackered. Any help much appreciated. Thanks.

 

[oz-plumber]

For a quick check, close the gate valve off that is connected to the myson pump. I have never seen a pump with a connection like that before, but I would assume it's on the suction side of the pump.
With both pumps running you may be draining the header tank and sucking air in that way. You may have to look at the header tank while you start up the system to see if that is the case.
To remedy the problem, you may have to check the water level of the tank. It may be ok while static but may not be while the heating is operating.

 

[Roger44]

Hi,

I did all of what you mentioned mate, still drawing in air, thanks though. Tank is full when running, I can see air bubbles coming up to the surface & the big vent pipe that goes up over the top of the expansion tank still makes a gurgling sucking sound. If you let the system run a long time, water Sodes out of the overflow and keeps dripping until you bleed all the rads again. I have noticed verdigris on the copper joint/nut on the boiler, the boiler was changed by someone from a local plumbers a few years ago and that is when the air in the system thing started, it's an old baxi bermuda back boiler. Could the verdigris be a sign of a leaking joint? Could this draw air in to the system? The joints are 22mm pipe, what's the best way of sealing the nuts/joint apart from a copper washer? Many Thanks!

 

[Roger44]

Just been up in the loft again and noticed the vent pipe is only about 3 inches from the top of the water level in the F & E tank? A chock of wood had dislodged by one of the rafters causing this to drop down into the tank and stop on the top of the tank. I've pushed the chock of wood back in under the pipe and it's raised the level of the vent, it's now about 13 - 14 " from the water level. Could this cause air problems? If so why and why does the pipe have to be at least 18 " over the top of the tank? Many Thanks!