Bleeding a rad every day?

[Lobster]

I fitted a new radiator in the house before Xmas, which necessitated a drain down of my CH system. No problem with that; however ever since then we've been disturbed almost every morning by horrendous bubble noise coming from the en-suite bathroom towel rail.

I'm now bleeding it almost every morning and get a reasonable 'pfffft' of air our each time. I'd originally put this down to residual air in the system working its way round (my CH has always been very prone to airlocks etc when working on it). But weeks later, I don't believe that can possibly still hold true.

Where could this air be coming from? My system is sealed and fully pressurised; and I replaced the inhibitor[1] when I refilled it so this can't be corrosion. I'm a bit stumped.

Any advice appreciated.

[1] Which actually has just got me thinking on a related matter... when I poured in the bottle of Fernox, I used this same towel rail to do so, because the access is dead easy that way. However, this towel rail is on the primary circuit so it warms up with the hot water rather than the rest of the central heating. Would that imply that actually there's now no inhibitor covering the rest of the house - ie, is it isolated?

[Kenny]

You are turning the heating off when you bleed the rad?

[Man at B&Q]

Check that by putting a match to the escaping gas. If it burns you have corrosion, but I doubt it would be enough to need bleeding every day.

MBQ

[Phil L]

Are any of the other radiators showing signs of air pockets? - cold at the top?

I'd bleed them all and see how it goes, FWIW I've bled rads up to six weeks after refilling, so there's every chance it will resolve itself over time if you keep bleeding the air out.

[Jonathan]

Why? I never have.

Jonathan

[harryagain]

If your pump has a cap over the shaft make sure it is airtight. If not air can get sucked in.

Do you lose pressure in the system? Do you lose water out of the safety valve? Check by tying a plastic bag over it and running the heating. (make sure system is bled and pressurised first)

If so the expansion vessel is buggered. When the sytem heats, if the EV is buggered water comes from the safety valve. When the system cools, suction draws air in.

[Huge]

Because the system can suck air in.

[newshound]

Indeed. Some do, some don't. My old Halstead combi did, my new Vaillant system boiler doesn't. All the same rads, just an extra loop to the cylinder.

[harry]

It can only suck air in if there is negative pressure. For that to happen, the expansion vessel would have to be naff.

[bert]

If the impeller is running it can create such a negative pressure depending on the relative positions in the circuit.

[harry]

The static pressure on the system by virtue of the pressure vessel). should be such that that can't happen. That's why it's there. The only exception being inside the pump housing.

[Jim K]

??? shurely you'd notice that no water came out of the bleed valve to signify the end of the supposed air venting??

also there is usally a distinctive smell to the "air" that should be coming out....

Jim K

[Rick Hughes]

If it blows the house up ... then you have cross connected gas & water

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