Surging noise when CH runs!

OPEN THE PLASTIC CAP A COUPLE OF TURNS. Wouldn't be much point having one if it didn't do anything.

Vent sucking half a glass is normal. Correct as long as it stops.

Thanks again ChrisR

I found an earlier message posted by davidf and the message header is Header tank flowing wrong way? This guy had a completely different problem to mine but some of the symptoms were similar.

I found by reading this message through that I found that the vent pipe should also be above the overflow. Now whether this actually makes any difference I don't know but I have also changed the position of the vent pipe so the end sits above the overflow.

I have also done as you suggested and opened up the top of the auto air vent about one full turn. No air came out when I took it off completely.

Do you know what sort of level the F&E tank should be at? And whether it actually makes any difference, just so long as its not overflowing.

It should only be about 100 - 150mm deep.
It musn't be too high, so there's room for the water to expand in when hot.

I reckon its about double that. That figure of 100-150mm, should that be from above the outlet? Or from the bottom of the tank?

Should I adjust this? And can this possibly be contributing to this rushing of air/water sound?

Just an update.

I have turned down the speed on the pump to setting 2 (Grundfos UPS 15-50) because I think the CH and HW is ok at that speed but I'm still noticing that the original problem of this intermitent rushing noise through the pipes (particularly when first starting up) is still occuring albeit maybe not as bad. I have done virtually most things suggested (thanks to all), but am wondering what to do next?

After looking at some other peoples problems I was just wondering if the air that I belive is still present in the system may be getting caused by one of my original actions which was to add sentinal X400 sludge remover. I flushed the system through about 3 times thinking that this should clear out any remaining X400 but now I'm wondering that I should have flushed it through more throughly.

Can anyone tell me from personal experience or other, whether if there is any X400 left in the system, that when X100 inhibitor is added that this could cause a chemical reaction problem where by causing gas bubbles to form which may be causing this ongoing problem?

Obviously if there is anyone out there with similar experience's do feel free to join in.

This is to ChrisR

Could you tell me if I should sort out the level in the F&E tank? Could this have anything to do with this problem?