I've just replaced a radiator after draining the system, I have turned the water back on and started the central heating but both the hot water is cold and the rads dont heat up - help!
Replaced a radiator
- Thread starter EddyBK
- Start date
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Air lock, check in air-in cupboard for any bleed valves. Then bleed all radiators.
Make sure pump is off when bleeding.
Andy
Make sure pump is off when bleeding.
Andy
Thanks Andy, the pump is working, but no water seems to have entered any radiators and where would the bleed valve be for the main system. It seems to be a pretty antiquated system
Have you a small (4 gallon) tank in your loft, and is there water in it?
John
John
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Yes there is a small tank and yes there is water in it
So when you open the radiator bleed valves, air should hiss out and be replaced by the water flowing from the header tank.....is this happening?
If not, there could be a blockage in the pipe leading from the bottom of the tank.
Look inside the tank - can you see the pipe outlet? Is there a layer of rusty gunge covering it?
John
If not, there could be a blockage in the pipe leading from the bottom of the tank.
Look inside the tank - can you see the pipe outlet? Is there a layer of rusty gunge covering it?
John
Hi John, No air hissing out and the water hasnt moved from the header tank. There is a little gunge around the outlet but I have pushed a wire cooat hanger in and it has gone all the way in suggesting that water should be able to move down the pipework
No air coming out means that water isn't entering the system due to an obstruction somewhere.
Give it a chance first by disconnecting one of the radiator valves, and then turning it on full. This may allow water to pass so prepare for any spillage!
Trace the pipe from the top tank as far as you can, and pass a magnet along it...if the magnet attracts then there are ferrous deposits within.
Its possible to blast mains water back through the rad valve if you want but you have to know whats what to do that!
John
Give it a chance first by disconnecting one of the radiator valves, and then turning it on full. This may allow water to pass so prepare for any spillage!
Trace the pipe from the top tank as far as you can, and pass a magnet along it...if the magnet attracts then there are ferrous deposits within.
Its possible to blast mains water back through the rad valve if you want but you have to know whats what to do that!
John
Thanks for this John, would this explain why there isn't hot water too. Funnily enough I've replaced about 6 rads here and never had a problem and the system was flushed through 2 years ago. I can only get a couple of yards down with the magnet and nothing so far - any other tips?
This small flow and expansion tank in the loft keeps the entire central heating system full, which includes the boiler, radiators, pipework and the indirect heating coil thats inside your copper hot water cylinder.
Water flow from that tank is negligible, hence crud in the system can build up, especially on pipe bends.
So, you drained that water away, fair enough but fresh water can't now enter your system for some reason (blockage).
Did you notice a pipe curving above the tank? Thats the expansion pipe which must remain clear...as your heating water expands, any excess causes the level in that pipe to rise.
You'll find that there is water at the hot taps.....but it will be cold. Thats because there is no direct connection between this domestic water and the water in your rads etc.
Hopefully this will help you to understand things a bit better - but it still doesn't sort your problem! Often pipework thats blocked has to be cut away, so do trace as much of the pipe as you can, and if there are brass compression joints its worth cracking them open.
On seriously bunged (or even air locked if your luck is in) systems the blockage can sometimes be cleared by connecting a mains pressure hosepipe to a radiator valve and allowing water pressure to force its way in....that expansion pipe has to be sealed for this and you have to consider that radiator pipework isn't at mains pressure anyway therefore its at risk....so lets hear what the others say!
John
Water flow from that tank is negligible, hence crud in the system can build up, especially on pipe bends.
So, you drained that water away, fair enough but fresh water can't now enter your system for some reason (blockage).
Did you notice a pipe curving above the tank? Thats the expansion pipe which must remain clear...as your heating water expands, any excess causes the level in that pipe to rise.
You'll find that there is water at the hot taps.....but it will be cold. Thats because there is no direct connection between this domestic water and the water in your rads etc.
Hopefully this will help you to understand things a bit better - but it still doesn't sort your problem! Often pipework thats blocked has to be cut away, so do trace as much of the pipe as you can, and if there are brass compression joints its worth cracking them open.
On seriously bunged (or even air locked if your luck is in) systems the blockage can sometimes be cleared by connecting a mains pressure hosepipe to a radiator valve and allowing water pressure to force its way in....that expansion pipe has to be sealed for this and you have to consider that radiator pipework isn't at mains pressure anyway therefore its at risk....so lets hear what the others say!
John
Air lock.
Put a hose pipe onto lowest heating system drain valve and open it, see if it started to run or not, if it does, leave it run a while then close and let it fill up and bleed rads.
If not, connect the other end of hose to main cold water and open tap slow, it will push back air out of vent and feed. Watch and make sure it does not overflow F-E tank.
Dan.
Put a hose pipe onto lowest heating system drain valve and open it, see if it started to run or not, if it does, leave it run a while then close and let it fill up and bleed rads.
If not, connect the other end of hose to main cold water and open tap slow, it will push back air out of vent and feed. Watch and make sure it does not overflow F-E tank.
Dan.
P.S Hopefully Andy is right - its just airlocked.....but usually at least one radiator should co-operate!
John
And Dan!
John
And Dan!
Have I missed it, why has a blocked cold feed pipe not been suspected?
Where the (usually) 15mm pipe from the header tank connects to the system is where I'd be looking for a blockage.
Where the (usually) 15mm pipe from the header tank connects to the system is where I'd be looking for a blockage.
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