Bleeding Air from Hot Water Tank Coil

[ribalta]

Hi there,

We have a sealed central heating system with a water tank. Every time the hot water goes on, the pressure in the system goes down by 1/2 a bar and there is a gurgling sound which I believe is because of air trapped in the pipes. I believe there is a way to bleed the coil going into the water tank but I have no idea how to do that?

Would anyone be able to explain how we can do it? I'm attaching photos.

Thanks!

Juan

 

[oldbuffer]

1. You have an automatic air bleed valve already installed. First picture (....912.jpg), left hand side , on the lower pipe going into the cylinder. Its a brass fitting sticking up from the pipe. Run the system until hot, turn off, leave for 15 minutes, slacken the cap (same size as a car tyre pressure cap) on top of the bleed valve. Allow any air to hiss out. The cap shouldn't need tightening, but those valves have a habit of sticking and then leaking, so I'd re-tighten the cap.
2. The pressure can go down anyway depending on pump direction, but this shouldn't cause gurgling.

 

[ribalta]

1. You have an automatic air bleed valve already installed. First picture (....912.jpg), left hand side , on the lower pipe going into the cylinder. Its a brass fitting sticking up from the pipe. Run the system until hot, turn off, leave for 15 minutes, slacken the cap (same size as a car tyre pressure cap) on top of the bleed valve. Allow any air to hiss out. The cap shouldn't need tightening, but those valves have a habit of sticking and then leaking, so I'd re-tighten the cap.
2. The pressure can go down anyway depending on pump direction, but this shouldn't cause gurgling.

Thanks for this, pardon my ignorance... Do you mean the small threaded one or the whole top? How do I slacken it? Thanks

 

[oldbuffer]

1. The small threaded one only. Do not attempt to undo the whole top.
2. From your latest photograph it looks as if the cap has already been removed. If so, there is nothing further to be done with the valve.
3. If the cap has not been remove, proceed per post #2.
4. The cap should unscrew in the normal direction (anti-clockwise looking down on it) with firm finger pressure. If not, use a small pair of pliers.

 

[ribalta]

Yes there is no cap like you say... So do I need to change the whole valve if no air is coming out of it? Thanks

 

[oldbuffer]

1. There is no point changing the valve. If there is no air coming out and the cap is missing it suggests:
1.1 The valve is faulty. Unlikely.
1.2 There is no air in the system.
2. If the valve IS faulty, changing it requires the system to be drained down to below the level of the valve. This could be a DIY job, but I'd only suggest it for the fairly experienced.
3. What gauge are you looking at to determine the pressure drop?
4. In your original third photograph there are two tun dishes, side by side. The further away one looks as if it may have had water running through it. If so, it suggests the hot water cylinder needs servicing. It is an unvented cylinder, and may only be serviced by someone with a current "G3" accreditation. Definitely not DIY.

 

[ribalta]

Thanks for your answers...

The pressure drops in the expansion vessel (see photo).

I have recorded the sound when the water is turned on (see zip attached). So I think there must be air in the coil?

I will ask regaring the servicing of the cylinder