Cold Rads Downstairs

Posted by an Ex-Royal Marine and used to warmer weather!!!!

Over the past week, the radiators down stairs are cold,(started last weekend in fact). Previuosly all ok.
Gravity system.
Boiler and pump downstairs.

Symptoms.......
All upstairs rads are hot.
Two downstairs rads are hot
The remaining 6 downstair rads are cold.
Hot water to all parts of house.

I have tested all rads for bleeding. Water comes out all, no air.
Sometimes some of the 6 rads may be tepid.

I have tried turning off all rads except one of these, result; just turns tepid or stays cold.
I have an electric pump which seems ok.

Can anyone suggest what the problem could be and supply an answer.
Thanks

Your pump could well be knackered,...hot water will always rise to the top ie make its way upstairs bypassing your downstairs rads.

Hello MrBob,

Martyc is right that the hot water will rise up to the bedrooms but 4 or 5 rads including 2 downstairs the pump is doing is job or the bottom 2 rads would also be tepid rather than hot.

1)When you bled the rads is the water relitively clear or a dark murky colour?
2)Have you recently started using the heating again?
3)Do you have TRVs on the rads?

Pump may just be stuck. Remove silver screw in the center and insert a flat bladed screwdriver. Locate on the spindle and try to turn.

It may need quite some effort. This is common on a gravity system as the pump is not used during the summer.

If this fails replace the pump.

Thanks for your comments so far......

Update.

The pump is working fine.

I have turned off all upstairs rads and turned off water heating and turned up temp, and turned off all but the furthest rad from boiler. This comes through hot.
I then do the same with all downstairt rads to see if I have an air blockage. I can make all rads downstairs hot.

I then turn on upstairs rads and this cools down the downstair rads, if I then turn on water heating element of system, downstairs goes cold.

I have checked for air in system and bled rads - none!

Water from rads is clear.

I have been told that my upstairs pip circuit is seperate from the downstairs pip circuit???? Can this be?

The system has worked OK in the house for the past 5 years.
We do not turn it off in summer, only right down.

I am willing to work through this fault by a process of elimination.

What can I check/do next?

On the heating flow pipe from the boiler there should be an antigravity valve usually within a couple of feet , it is brass about 4 inches long. It is not unusual for these to jam and not to open properly.
So it restricts the flow to rads will let some work but not all ,a sharp hit with a small hammer can free them but they only cost about a fiver so best change it

I suffered a similar problem and the solution was to "power flush" the radiators by using a temporary connection to the main cold water supply. This flushes out any sludge which may be blocking or slowing down your CH flow. But it can be a lengthy procedure.
First drain the radiators; fit a stop cap to the 22mm CH vent which is above the CH header tank-important or you will have loads of water gushing into the header tank!; fit a drain hose to your lowest radiator drain cock; make a temporary connection between the cold water supply and a nearby radiator e.g. by removing a top bleed valve and connecting pipework to a nearby cold water supply.

Then close all radiator valves except one and turn on the cold supply.......this way you can force water through the rads at a reasonably high pressure. Open one radiator valve at a time until all have been flushed. Remove all temporary pipework, stop cap, re-fit bleed valve and refill the system.......... Good Luck with that lot.....it took me half a day but the result was that all radiators came on together again and I knew there was no sludge anywhere.

Regards
Greenflag

Can I ask if and how you resolved this problem MrBob, as I am having exactly the same problem. 6 rads up 5 down.

open vent means you won't go wrong very often by saying it could do with a clean.
when that is done, convert to fully pumped; it will make the heating a lot quicker, the hot water quicker and should even give you a modest saving on your gasbill.
if you really want to improve things, you should also change it to a sealed system.