Old un-pressurised heating system - top up valve

[JohnMalcolm]

Hi All,
I hope you are doing well.
I have old un-pressurised heating system and I need to top up the water but I cannot locate the bloody valve.
Where is it? Is it in the attic?

I also have this valve with black screw on top. Should this be opened or closed?


Thank you

 

[ShaunCorbs]

Chances are they will be a tank in the loft

Open when filling up closed when full

 

[JohnMalcolm]

Chances are they will be a tank in the loft

Open when filling up closed when full

In the loft I have two tanks, one much bigger than the other and both are not empty. I still wonder how I filled the system initially when it was completely drained. Intake water pipes that go into the tanks have a regular valve but also the float valves.

 

[Basher]

In the loft I have two tanks, one much bigger than the other and both are not empty. I still wonder how I filled the system initially when it was completely drained. Intake water pipes that go into the tanks have a regular valve but also the float valves.

The smaller of the tanks in your loft is likely the F & E tank for the central heating, which should be automatically keeping the system topped up.
Is the tank full, with the ball raised floating on the water, and if you push the ball down does the valve let water into the tank?

What leads you to think the water needs topping up in the first place?

 

[JohnMalcolm]

The smaller of the tanks in your loft is likely the F & E tank for the central heating, which should be automatically keeping the system topped up.
Is the tank full, with the ball raised floating on the water, and if you push the ball down does the valve let water into the tank?

What leads you to think the water needs topping up in the first place?

Thanks for clarifying. Yes, the ball valve when pressed releases some water.
The reason I think there is air in the system is because this valve on the above picture was opened for a prolonged time but this is to do with hot water tank so has nothing to do with heating circuit, right? The valve has now been closed.
When the boiler kicks in I can hear the water slushing in the pipes in the area where the tank is. I don't think I could hear it before but maybe is just I am more sensitive, paying more attention to the noises coming from the heating system.

 

[Basher]

I would expect that automatic air vent you show in the photo to be installed on the heating circuit, maybe the heating coil in the cylinder, or an otherwise high point in the heating loop. They can be left open but have a reputation for leaking out of the vent, so it's preferable to just open them when needed and close again.

 

[Basher]

When the boiler kicks in I can hear the water slushing in the pipes in the area where the tank is. I don't think I could hear it before but maybe is just I am more sensitive, paying more attention to the noises coming from the heating system.

I came across a mention here of someone who had a 'swooshing' sound from their hot water cylinder when the system was heating water, and one response suggested there might be air in the coil. If your air vent is on the coil, maybe it's become caked up/blocked through being open a long time, and there is air that can't get out!
Just a thought!