COLD BABY - hot rads downstairs cold upstairs

20 Sep 2007
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United Kingdom
I drained down system to add a rad and move another downstairs. These rads are still off but central heating system is refilled and on (i.e. valves to these rads are closed). Conventional boiler with pump and feed&expansion tank in loft.

I get heat on downstairs rads but not upstairs. Have checked:

Boiler fires and rads heat up downstairs.
Pump works (as have replaced and can hear movement)
Gate valve is locked open.
Feed & expansion tank in loft is full
All rads upstairs cold (heat reaches the TRV on first rad upstairs but does not penetrate rad even though TRV is open)
Have bled rads throughout house.

Any suggestions as we are having to move baby downstairs for heat at night.

Can this be an airlock upstairs? If so how does one fix?

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I am poor on definitions.

Two pipes run through the system - one carrying hot from boiler the other cold from end of rads. Rads branch off from the 22mm pipes as they run through house (as far as I have taken floorboards up in the past).

The 2 rads disconnected downstairs are branches off the 22mm pipes so I do not see them breaking the flow of water (indeed the 22mm pipes to touch are hot as they run past the branches for these 2 rads)

Is this question?
Shut off all but one radiator, and turn the pump to full speed. It will probably shift quite a lot of air in the pipes. Then repeat for other rads.
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Didn't work. I have no shut off valve to my central heating tank which means that given two paths of blowing out an air bubble and cycling through the tank it looks to be going for the latter (i.e. least resistance).

I could put a valve in to allow me to shut off the route to the tank (which would make my system more efficient anyway) and then try again. In doing so I have to drain down the system anyways which may clear problem.

Job for the weekend now I think.

Old house - never simple. Thanks for the tips.
just to check

something like this often happens when a rad has been taken off e.g. for decorating

if you open the bleeed valve on one of the upstairs rads, does water squirt out forcefuly?

What colour is the water?

Did you get any black sediment when you were draining?

What do you mean by "cycling through the tank"? Is it coming out of the vent pipe above the Feed & Expansion tank? Or do you mean the hot water cylinder seems to be stealing too much of the flow?

If you have closed the downstairs rads and the pump is working, where would you say the flow is going?

Is the cylinder upstairs?

Can you lay your hands on a strong magnet?
No - upstairs water does not squirt out forceably.

Water is clear - very little sediment (have flushed out each readiator individually in the last year).

By tank I mean hot water tank. So - if upstairs is air locked and rads are closed downstairs then water still has two routes left - the hot water tank or moving the airlock upstairs. The flow is currently going through the hot water tank.

How water cylinder is downstairs.

Magnet - no. Do I need one?
David H said:
By tank I mean hot water tank. ...
and by tank you mean cylinder? Is there no motorised valve to stop supply to the cylinder once it is hot? Or a Cyltrol valve?

David H said:
No - upstairs water does not squirt out forceably...

is the F&E in the loft? How high above the rads?
What happens when you bleed the upstairs rads? air? water dribble? nothing?

Do you have a drain cock downstairs to empty the CH system?

humour me ;)
tie up the ball cock in the F&E (to stop it refilling) and mark the water level (should be about 2 inches deep)

Drail a couple of galls out of the bottom into a bucket (so as not to waste your inhibitor)

climb back into the loft with your bucket and see if the F&E level has dropped by the amount you drained out.

p.s. the magnet will cling to any copper pipes which are blocked with hardened black sludge. This is almost always where the feed pipe from the F&E joins the main pipes at a Tee
Hot water tank - not sure of diff tank and cylinder. Large metal vessel shaped like sausage. Hot water pipe I think runs through in coil to heat surrounding water in vessel.

F&E is in loft - so floor above.

When I refilled CH system the rads upstairs did not refill quickly. Did at first but then slowed down to point where air dribbled out. This has happened in past but pressure seemed to improve within a couple of days. Not this time. Why I thought air pocket upstairs (pressure downstairs is good and water squirts out).

Will try the F&E and drain cock downstairs trick tonight. What will this tell me?

Should I wait for outcome of this before trying the magnet? I ask as I think the tee where F&E joins CH system is under a laminated floor upstairs.
if the supply from the F&E is obstructed in going down into the radiators, then the level will not drop when you drain. this implies a blockage. In which case you may need your magnet.

The lack of squirt from your upstairs radiators suggests this might be the case. This is often noticed after a rad has been taken off for decorating.

If this is not the problem, then controlling the water going through the cylinder coil would be a good move.

Cylinder (note it is cylindrical in shape) which is closed at the top


Cistern (open at the top but has a removable lid) often called a tank. Older houses usually have a large cold water storage one, and a small feed and expansion one for the boiler.


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