New Radiator have to bleed regulary

micks_address

Hi Folks,

Question - couple of months ago we got a new kitchen installed and as part of that, moved a rad from its old position to a new position in the room. Its the first rad on the pipes from the boiler so heats very quick, but i notice i have to bleed it regulary. It was a new radiator that we fitted. The old radiator was under a radiator cover and suffered the sample problem (only we didnt bleed as often due to the hassle of taking off cover)

We hadnt the heat on for the summer and switched it on the other night, noticed the rad cold so bled loads of air from it. Why would so much air be getting in to it and is it the sign of a bigger probably we should be worrying about?

Cheers,
Mick

nmacc

What you have there is most likely not air Mick, but a product of corrosion in the system.

The black gunk that comes out of radiators is called Magnetite and is a form of rust. Your heating system is made up of four different metals: steel in the rads, copper in the pipes, brass in the fittings and cast iron in the boiler and pump. In a gas boiler you'll also have aluminium in the heat exchanger. Immerse all of these in water and add a little oxygen and you have a chemical soup which will rust the radiators and boiler & give off gas in the process.

You need to add a chemical inhibitor such as Fernox to prevent the corrosion. Usually one container for every 100 litres, which is usually approximated to 10 rads. Better to add too much than too little. That should eliminate the bleeding, unless you have a leak which allows the water to drain away and thus the inhibitor concentration drops over time.

Dtp1979

nmacc wrote: »

What you have there is most likely not air Mick, but a product of corrosion in the system.

The black gunk that comes out of radiators is called Magnetite and is a form of rust. Your heating system is made up of four different metals: steel in the rads, copper in the pipes, brass in the fittings and cast iron in the boiler and pump. In a gas boiler you'll also have aluminium in the heat exchanger. Immerse all of these in water and add a little oxygen and you have a chemical soup which will rust the radiators and boiler & give off gas in the process.

You need to add a chemical inhibitor such as Fernox to prevent the corrosion. Usually one container for every 100 litres, which is usually approximated to 10 rads. Better to add too much than too little. That should eliminate the bleeding, unless you have a leak which allows the water to drain away and thus the inhibitor concentration drops over time.

Yes inhibitor is the answer I'd say but it's absolutely useless adding it to a dirty system so don't waste your time or money. Get the system powerflushed first and when it's clean, then add the inhibitor.
Actually an old wise man once told me that adding inhibitor to a dirty system can create a mix that is corrosive to plastic piping like Pex. How true that is I'm not sure.

tashiusclay

Is the radiator that's currently needing bleeding the closest one to the hotpress, or circulating pump? If the pump is in an incorrect position in relation to the heating system cold feed/supply pipe on an open vented system this can cause the pump to suck in air via the cold feed pipe and this air usually ends up in the nearest radiator to it. Check the radiator location, especially as the old rad had the same problem before you moved it.

micks_address

its the one closed to the boiler and the circulating pump is on top of the boiler. It isnt a huge issue, just have to keep an eye on it.. once a month is probably enough to bleed, but was full of air after the heat being off for the summer time

tashiusclay

micks_address wrote: »

its the one closed to the boiler and the circulating pump is on top of the boiler. It isnt a huge issue, just have to keep an eye on it.. once a month is probably enough to bleed, but was full of air after the heat being off for the summer time

In that case, if the pump is fitted to the outward flow pipe of the boiler, check that the automatic air vent/bottle valve on the boiler, if there is one fitted, isn't fitted behind the pump, causing the pump to create negative pressure between it and the vent, thus allowing the vent to suck in air.