Radiator removal with strange findings!

[BBay55]

Recently moved into Victorian house that needs renovation. Trying to do stuff for myself as no money left and I want to do it anyway!
Wanted to remove radiator for decorating. I closed off both valves (1 may not be fully closed, but I think they are).
I should say this radiator has not got warm in any way since we’ve been here, all the other radiators work and we have an oil boiler.
Anyway back to removing radiator. I loosened nut as your supposed to, and started to drain the water. There was a bit of mucky water that came out but after about 1/2 large bucket it was running clear.
Then I realise the pipe that feeds the radiator is getting warm. I loosely tightened valve to stop the flow and on investigation found that the pipe coming under the floor boards is now warm as is the pipes leading to it from another room.
I went back & drained some more water in the hope I could do it. But then gave up as it’s lovely warm water.
I’ve righted nuts back up and left for plumber but maybe it’s simple?
Do you think the radiator could be connected to the hot water supply as it’s just like when you turn a trap on. I loosen the valve the water becomes hot. Tighten it back up and pipes go cold pretty quick.
I am waiting for a plumber but just wondered if anyone has ever experienced anything similar!
Many thanks

 

[Mike13]

did you get warm water from both ends? the blockage could be in the rad, or just in one feed pipe.

 

[Hugh Jaleak]

Did you get warm water at just one end, or both? Quite possible that one valve is stuck shut/pipework other end is blocked or as said, Rad itself is blocked. 'Murky water' would be expected from a heating system, especially if there is insufficient inhibitor in the system.

 

[BBay55]

I only tried to empty it the one end. The dirty water came out as expected but then it started to run clear and that’s when the water & pipe got hot. I should have said these pipes have never got hot before and the heating systems off.
When I had the heating on last night these pipes were stone cold.

As an aside which makes me think there is something going on with the hot water, the kitchen tap has to be turned fully on hot and run for ages at a trickle before it gets hot. The valves are fully open and it gushes on cold & even what should be luke warm. All other hot taps are fine and have piping hot water within a few mins. This radiator is next to the kitchen!

 

[Madrab]

When you say it may something to do with the hot water? Do you have a hot water cylinder and has the central heating been on to heat that? You may find that you have opened the return leg of the feeds to that rad and you are pulling the return water from the system.

If you can get the rad off then open each valve separately and see if you get flow from both. Is it a sealed system or is it open vent with a small cistern in the attic? You may have got 1/2 a bucket of dark water if the rad hasn't been working for a long time and the system water has just been sitting in the pipework for a long time and you're flushing it through

 

[BBay55]

Thanks. It’s an old system with a tank. I don’t think it’s vented as when I had a plumber out originally to get the radiators working he was talking about swapping for a vented system.

I can take the radiator off. I just stopped as was nervous of making a mistake. I shall open the other end and see what happens!

 

[Madrab]

It’s an old system with a tank

If it has the small tank in the attic then yes, it's what's called an open vented system.

Your plumber may have suggested that it goes to a non vented system, which would normally be called a sealed system.

As long as you isolate both valves and there's no water leaking from them, then it would be ok to remove that rad. Even if the vales pass a little you can cap the valve to stop that.