Not the usual stuck TRV cold radiator problem

[carlBrown]

Hello all,
First of all, people on here seem to know what they're talking about. I've been through all the FAQs and common problems pages, plus trawled through lots of forum posts where people are having similar problems as me, but so far they've all been fixed by simply tapping the TRV pin. This hasn't worked for me! So i thought i'd finally post and see if someone can help me out.

We bought a 2nd floor flat in the summer, recently turned on heating and one radiator (master bedroom) is stone cold, and both pipes leading into it were cold too. Apparently boiler has been regularly serviced for many years. and i think it's probably the furthest rad from the boiler.

It's a 2 pipe system and all radiators have TRVs fitted to one end and at the other is the normal control flow valve (not a lock shield, which i'm slightly confused by too? i thought the TRVs were supposed to be replacements for the flow valve not the LS valve? unless they've all got the wrong cap on and are actually LS valves?)

Now, i've tried hitting the pin and nothing happened (Have had success with this method in the past on a different rad however). Read lots of posts, saw a few suggesting turning all other rads off and leaving the cold on one, then jack up the pressure and see what happens. Did this, pressure at 2 bar (poss a bit high?) left it running on max heat for 15 mins and finally the pipe leading to the TRV started getting hot. Joy i thought, but then nothing more. That end of the rad started to get lukewarm at best, but i put this town to heat transfer through the metal as nothing more happened.

Have bled all radiators now, no air anywhere.

The odd bit, that i'm sure someone here will be able to help with, is this: I cracked the nut joining the TRV to the radiator, hot water came out for 2 seconds, then stone cold (presuming it just drained the water that had heated through transfer, then that left only the cold water in the rad to come out) so i thought, it must the TRV is stuffed. I'll get t a new one.

Then i read another post on here from someone saying crack the other end and see what happens, it might not be the TRV. So i did.
When i opened the nut at the other end (control flow valve NOT TRV) suddenly hot water came flowing out and the other pipe going into the ground got hot. Until i tightened the nut up again, then the heat slowly dissipated leaving me feel very disappointed!

So i'm totally confused. The pin in the TRV moves freely, so is the valve itself knackered?
The control flow valve moves freely, but maybe that valve is knackered?

Or might there be an airlock somewhere else?

Or am i describing the symptoms of a rad filled with sludge that needs draining and flushing?

Any help would be very much appreciated as it is getting cold in there and it's only going to get worse!

Carl.

 

[stevetheplumber]

pin can move and valve still be stuck shut the return valve trv open and draw water from vent into a bowl if it stops after a few seconds(20) the valve is jammed shut

 

[carlBrown]

pin can move and valve still be stuck shut the return valve trv open and draw water from vent into a bowl if it stops after a few seconds(20) the valve is jammed shut

Thanks for that Steve. Can i just confirm what you mean...

Shut off valve at opposite end from TRV. Open TRV, then open bleed nipple and wait to see if water stops coming out of it? Is that what you mean by vent? Sorry, i'm sure it's a dumb question and i can't image what else you could possibly be referring to, but want to make sure!

Cheers, Carl.

 

[tackleburger]

Did you not say you already had hot water at the TRV & lockshield sides. If so close both, open bleed valve to take pressure of rad. ?Remove radiator take outside and empty flush if necessary. Get a basin and with all other rads off open the trv until water runns clear thern do the other side. You mayt need someone on the filling loop to help you. You should get water out of both ends. At this point you may opt to drain down and change the valves anyway depends on how old they are etc etc. If not fit radiator and bleed. Start heating all should be well.

 

[stevetheplumber]

Thanks for that Steve. Can i just confirm what you mean...

Shut off valve at opposite end from TRV. Open TRV, then open bleed nipple and wait to see if water stops coming out of it? Is that what you mean by vent? Sorry, i'm sure it's a dumb question and i can't image what else you could possibly be referring to, but want to make sure!

Cheers, Carl.

yes through the air vent this will confirm flow or notif you shut both valves you can take the pin right out to let it flow from each valve seperately hold a bucket up to catch water

 

[carlBrown]

Did you not say you already had hot water at the TRV & lockshield sides. If so close both, open bleed valve to take pressure of rad. ?Remove radiator take outside and empty flush if necessary. Get a basin and with all other rads off open the trv until water runns clear thern do the other side. You mayt need someone on the filling loop to help you. You should get water out of both ends. At this point you may opt to drain down and change the valves anyway depends on how old they are etc etc. If not fit radiator and bleed. Start heating all should be well.

Yeah i did say that. When i crack the nut on the control valve / Lockshield end hot water comes out and the pipe leading into the TRV is hot too.

I'm going to test whether it's the TRV stuck closed (irrespective of pin movement) and then (as i'll have to do it anyway) get the rad off the wall. I get the impression that if it's free it would be a good idea to flush it anyway, then at least i can see the condition of the water within it.
I take it if it's really black and horrible i should really drain / flush the system and re fill with inhibitor?

Thanks your yours help so far gents!

Carl.

 

[paul H]

carl its sounds like you need the radiator and pipe work power flushed to clear debis / air pockets out of the pipe work

 

[carlBrown]

carl its sounds like you need the radiator and pipe work power flushed to clear debis / air pockets out of the pipe work

Power flushed? I'd heard that this can cost upwards of £500! I don't have that sort of money. If i did i wouldn't be trying to fix it myself!

Is that something, if i was feeling brave, that i could do with a compressor and lots of sheets? I figure if i hook up the compressor somewhere in the kitchen, then have the only exit in the bathroom then it will be easier to clean up when the black gunge goes everywhere?!!
Possibly a foolish thing to suggest.

 

[REDSAW]

Power flushed? I'd heard that this can cost upwards of £500! I don't have that sort of money. If i did i wouldn't be trying to fix it myself!

Is that something, if i was feeling brave, that i could do with a compressor and lots of sheets? I figure if i hook up the compressor somewhere in the kitchen, then have the only exit in the bathroom then it will be easier to clean up when the black gunge goes everywhere?!!
Possibly a foolish thing to suggest.

go for a chemical flush carl, about £15 and can diy, buy a rubber mallet to bang the rads.

 

[Puddle]

Were did the chemical flush come from !!

All radiators getting hot apart from bedroom,alot of people close this rad valve down as do not like bedroom to hot
So probably thermostatic valve stuck,these can sometimes be freed off by banging but not always
you can try removing/wigaling pin,the other valve leaked probably because when lock shield valve tried to be opened either complete top moved with spindle ,loosening from body or body nut moved instead of spindle,hot water will leak out if system on,shows clear
as said most likely valve stuck,if you can not free off, requires removing and freeing off or new fitted
And going by recent pricing on here it will only cost you £14.00 plus £8.00 for new valve so for £22.00 you can have a new valve fitted but would allow a pc price of £100 just incase pricing slightly out

 

[swansojb]

I had this regularly at my aunt's house in a high hard water area. Because pin is not attached to valve, only pushes against it, pin can be free but valve stuck as pin only pushes valve shut. Only solution was to drain down system, remove faulty valve and push valve seat to free it. If a valve stuck regularly, fitted new TRV. Use a soft tool, eg small wooden spoon handle so as not to damage valve seat. Used to have to do several valves every year. If a valve stuck regularly, fitted new TRV.

Long term remedy would have been a complete clean out, new TRVs, and maybe getting a water softener, but house was sold before I got that far.