Flushing out noises with mains pressure water

[sleepless]

Hi

I have a gas CH/HW system, with a Potterton Suprima boiler on the wall in the garage and a Grunfoss 15/50 pump in the airing cupboard next to the hot water cylinder. Oher than a single air release thingy near the pump, the only bleed valves are on the rads.

I recently drained my CH/HW system (to fit some TRVs). Since refilling the system, I'm getting all sorts of noises.

I've been running the system with all rads except one off and the boiler stat down at the lowest point, to try and release what I think is trapped air. I can clearly hear air in the system, (as it approaches the pump there's knocking, then the sound of air being 'chopped up' in the pump, then I can hear bubbles entering the rad). But when I go to bleed the rad, there's no air !!??).

The noises are worse when the HW is on.

I've tried running the pump at various speeds, and I've tried using a different rad each time, but this hasn't helped. I've also bled the pump.

I've heard that I can possibly flush out any remaining air blockages using mains water pressure, but I'm concerned about the effect thtis'll have on the boiler and pump.

I'm desperate for advice on flushing or any other suggestions that may help.

 

[oilman]

The easiest solution would be to drain the system, and add some bleed points in the places where you would expect air to get when the system is first filled. This sounds like a major job, but you will be able to fill the system so much easier, and clear the air that lurks in the system for a few days.

 

[sleepless]

Thanks for the suggestion. Unfortunately, we've just had new carpets / flooring laid in all rooms, so that's not really an option.

Any other suggestions??

 

[COG]

You say you have a vent near the pump ,do you no what type or can you describe it. You should have one at the top of the coil feeding the cylinder ?. Did you vent the system with the boiler off and any motorised valves held open.

 

[sleepless]

The vent is just a screw off cap at the top of an upright pipe leading from the pipe that's on the HW side of the motorised valve. I get a little air from here sometimes when I'm bleeding the rads. There's no oher vent on or near the cylinder.

The boiler was off when I drained the system, but I'm not sure what the situation was with the valve (I'm thinking that it may well have been set to CH only.......).

Perhaps I should drain the system again but make sure that the valve is set to the mid-way position when I re-fill ??