Air in hot water circuit after draining system?

[charding370]

Recently did a complete system drain and refill. All rads are nice and evenly hot, but hot water is not as hot as before.
The hot water system that has a circ. pump and seems to have air in it as when the C/ H stat goes to off the boiler doesn't fire up for ages until the hot water flow pipe cools down, indicating to me there is air in the system.
How can I get the air out, there appears to be a relief valve in the boiler pipework after the c/h circ.pump at the top of a vertical pipe, does this need opening to release any air blocked in it or is it a pressure relief valve? I know this is not the hot water circuit as such but its all part of the central heating circuit on my old fashioned system.

 

[echoes]

Does it look like this?

If you open this slightly then you can let the air out in the same manner as bleeding a radiator. Beware if it hasn't been used for ages - the rubber washer inside can stick.

Or this

Make sure the little cap isn't screwed down tight and then it should vent any air automatically.

 

[charding370]

Yes, it looks like the top picture but it has a knirled roudn finish not flats on it and its on the end of a pipe that is on the c/htg flow side just after the pump but inside the boiler casing.
Can you unscrew half a turn when the system is off/cold? It has been on ever since the boiler was fitted over 10 years ago. Do you think I need a plumber incase this rubber washer leaks everywhere?

 

[echoes]

Yes just unscrew it slightly with your fingers to vent any air. If air comes out, or a dribble of water, then it hasn't stuck. Is this the highest point on the system?? - you might find another one of these elsewhere, probably by your hot water cylinder. If so, bleed that as well.

 

[charding370]

I tried that but it wont budge, should I put some pliers round it?
I dont want to put too much force on it as its only 15mm copper.

 

[misterdubya]

I tried that but it wont budge, should I put some pliers round it?
I dont want to put too much force on it as its only 15mm copper.

Yes, if pliers are all you have. I'd use gordons personally.

Mr. W.

 

[charding370]

I tried that but it wont budge, should I put some pliers round it?
I dont want to put too much force on it as its only 15mm copper.

Yes, if pliers are all you have. I'd use gordons personally.

Mr. W.

Sorry Im not into this plumbing lingo, are they those like small size Stilson grips? I have a big pair or mole wrench but would not use either as butchers soft metal like brass.

 

[charding370]

I undid the knob and some blackish water came out, no hiss/ no air so I didn't pursue it any further. The chap how did the drain down reckons the only way is to beed all the rads again, I already did that a second time and there was very little aircame out. Is this the only way to get air out as boiler makes gurgles and wooshes when c/heating pump clicks on?

 

[misterdubya]

Have you bled the pump itself?

Mr. W.

 

[charding370]

Have you bled the pump itself?

Mr. W.

Yes, both C/H and hot water pumps just bleed water.