Help with my mystery of air in radiator system

[marc1977]

[FONT=&quot]Hi,[/FONT]

[FONT=&quot]Every week i have to bleed just one radiator in my house for about 2-3 seconds and i simply cannot find out why.[/FONT]

[FONT=&quot]- Its a sealed system and I can see no drop in the pressure. [/FONT]

[FONT=&quot]- Its the radiator closest to the boiler and pressure relief valve if that helps.[/FONT]

[FONT=&quot]- I can find no leaks anywhere in the house and have checked all the compression and rad valves[/FONT]

[FONT=&quot]- Ive checked the pressure relief valve but no leaks from their either.[/FONT]

[FONT=&quot]- there are alot of drops in the house (4) to downstairs rads and all the pipework was fitted about 4 months ago so its relatively new.[/FONT]

[FONT=&quot]Any ideas please as its driving me mad![/FONT]

[FONT=&quot]Thanks[/FONT]

 

[snowhead]

Do you turn the boiler and pump off when you bleed?

 

[marc1977]

No i dont. Could this really draw more air in?

 

[marc1977]

Actually i dont turn it off but the boiler / pump is not usually running when i bleed

 

[Alex Knight]

How old is the rad?

 

[marc1977]

that rad is about 20 years old...BUT all others in house are new

 

[marc1977]

we had most of the pipe work refitting to convert 1 pipe to 2 pipe so all new rads and pipe work BUT that rad was not chnaged

 

[Best]

I suppose you should have that old rad removed and thoroughly flushed out with garden hose to see if any crud lying in bottom causing gases to be released.
But I would find out if any auto vent has been fitted somewhere on suction (negative) side of system pipework. The auto vents on a return pipe can allow air to be sucked in when pump on. Manually close a likely auto vent to test

 

[marc1977]

the only thing i can think of is a bypass valve fitted near the boiler? there is no auto vent.

 

[zzzjim]

a) How many radiators in system
b) Where is boiler/pressure guage situated , upstairs or down
c) What Hot ( the highest seen) and cold pressure readings do you get ?
(If results are varied , Do the readings differ more when it is well bled )

 

[SquiresPlumbing]

Have you got any speedfit on the system? If it's not barrier pipe it will be drawing air In

 

[king of pipes]

Try fitting a Alladin auto vent you will find info at amazon .

 

[Vee]

You most probably have a leak somewhere. It will draw in air when pump is running and leak when it's not. Find the leak, it may be small. Another possibly is that you have another automatic vent on the system external to the boiler. This can also cause air to get in. Either replace with manual vent or keep shut if you have.

 

[simonwalk]

When you bleed the radiators does black water spurt out ? could be your radiators are corroded and the formation of iron oxide on the inside is producing small amounts of hydrogen.
System may need inhibitor or cleaning.