Topping up a gravity fed heating system

[Rbrt]

I need to top up the water in my radiator system.
I believe it is a gravity fed system.

There is a small expansion tank at high level in a cupboard. 
There are no bleeding ports on any of my radiators. 
Do I just top up at the expansion tank a little at a time until the level stabilises?

I have been told to just use engine coolant, is that ok?

Thank you for any advice given. 

[BWM]

10 minutes ago, Rbrt said:

I need to top up the water in my radiator system.
I believe it is a gravity fed system.

There is a small expansion tank at high level in a cupboard. 
There are no bleeding ports on any of my radiators. 
Do I just top up at the expansion tank a little at a time until the level stabilises?

I have been told to just use engine coolant, is that ok?

Thank you for any advice given. 

There should be some form of bleed device, but some systems have the open expansion tank at the highest point of the system - generally at the end of the run.

[Tony Brooks]

If the level is low - and that does not mean lower than a full mark on the tank, then just topping with a 25 to 30% antifreeze mixture should be fine.

 

If the liquid has disappeared down the pipe then you may have to bleed the system, but if you take it slowly it might self bleed.

 

WE had the no bleed points on the rad a few weeks ago, and the general opinion from the central heating bods was that you do, but have not located them.

 

 

[David Mack]

If this is a gravity system with a hot pipe running above the radiators from the top of the stove, and feeding the top connection of each radiator, and a  pipe below the radiators taking cooler water back from a bottom connection to the stove, then there may indeed be no bleed valves, and the system will be self bleeding.

On the other hand if both pipe connections are made to the bottom of the radiator then the system will be pumped and will need a bleed point at the top of each radiator.

[Tony Brooks]

46 minutes ago, David Mack said:

If this is a gravity system with a hot pipe running above the radiators from the top of the stove, and feeding the top connection of each radiator, and a  pipe below the radiators taking cooler water back from a bottom connection to the stove, then there may indeed be no bleed valves, and the system will be self bleeding.

On the other hand if both pipe connections are made to the bottom of the radiator then the system will be pumped and will need a bleed point at the top of each radiator.

 

Point of order. Jenny B had a gravity circulated system with the inlets and outlet in the bottom of the rads as per domestic single pipe system of yesteryear.

[Tracy D'arth]

I have never seen a radiator without a bleed nipple. They may have been installed upside down with top diagonal to bottom connections I suppose.

Many years ago we had a new VW Beetle in the garage that had no valve in one wheel. Expecting it to be on the inside we removed the wheel, it wasn't.

The explanation was that tyres were fitted to wheels at the tyre factory and blast inflated to 2 bar in a pressurised cage for speed and safety so it mattered not that the hole for the valve had never been punched and no one needed to check. Presumably the man that fitted valves thought it was funny and passed the wheel on.

[MtB]

9 hours ago, Tracy D'arth said:

I have never seen a radiator without a bleed nipple.

 

I've seen thousands.

 

Back in the day, rads came with four 1/2" BSP tappings, one on each corner. It was the installer who then fitted a plug, rad valves and a bleed valve in whichever corners necessary.

 

On proper gravity systems a bleed valve would have been pointless. Still regularly seen in the big country houses with a whopping big oil boiler in the basement when I was new at it 50 years ago. 

 

 

The cast iron column radiators often used in such systems however, came with 1 1/2" tappings IIRC! 

 

 

[Tracy D'arth]

7 hours ago, MtB said:

 

I've seen thousands.

 

Back in the day, rads came with four 1/2" BSP tappings, one on each corner. It was the installer who then fitted a plug, rad valves and a bleed valve in whichever corners necessary.

 

On proper gravity systems a bleed valve would have been pointless. Still regularly seen in the big country houses with a whopping big oil boiler in the basement when I was new at it 50 years ago. 

 

 

The cast iron column radiators often used in such systems however, came with 1 1/2" tappings IIRC! 

 

 

OK, lets clarify. I have never seen a modern steel radiator without provision for a air vent.  And unless installed on a gravity system with flow at the top it must have an air vent.

We are talking boats here, not with cast iron sectional antique radiators nor are we talking about when I started plumbing in steam pipe 64 years ago on country houses of the landed gentry.

If you go to the Metal Box Company, Stelrad, you could see millions of radiators without the vents and plugs screwed in.

[Rbrt]

On 07/09/2023 at 15:34, David Mack said:

If this is a gravity system with a hot pipe running above the radiators from the top of the stove, and feeding the top connection of each radiator, and a  pipe below the radiators taking cooler water back from a bottom connection to the stove, then there may indeed be no bleed valves, and the system will be self bleeding.

On the other hand if both pipe connections are made to the bottom of the radiator then the system will be pumped and will need a bleed point at the top of each radiator.

My pipe work is into the bottom of the rads like a standard type system but I’m certain no pump for the heating. 

I’m back at the boat later so will look again for bleed nipples. Thank you for the advice so far. 

[Tracy D'arth]

3 minutes ago, Rbrt said:

My pipe work is into the bottom of the rads like a standard type system but I’m certain no pump for the heating. 

I’m back at the boat later so will look again for bleed nipples. Thank you for the advice so far. 

Air vent will be either in one end of the rads or some now are on the back sides top about 6" from one end, in between if double rads.