Combi Boiler - one radiator not heating at all

[johnpaul.gordon]

Hello,

I know this topic has been done to death but I have tried almost everything I can find online and I would welcome any advice on the problem with my radiator before I call in the plumber.

Right so my radiators all work from a Worcester Combi boiler (5 years old) sealed system, there is one towel radiator (non TRV) upstairs that does not heat at all, it definitely used to very well.

Every other radiator is piping hot very quickly and even the tail pipe to the radiator is very hot, so it is just this isolated point.


Already tried:

Bleeding the radiator
Balancing the System (adjusting TRV etc)
Draining the system and replacing the valves on both sides
Removed the radiator and hosed it out from all ends,it was filthy and full of sludge
Bleeding the system after refill.
I have added in some Fernox F3 and will let it run through for a week but I am concious that if there is a partial blockage it might not be that effective as it wont be able to get to the problem point, but there is no harm in cleaning anyway.

Although the radiator was full of sludge it still does not heat now that it is cleaned out, the tail pipe and inflow valve are piping hot but the radiator itself is not heating one bit.

There is definitely some water passing through the inflow valve as I can hear it and I have demonstrated it by shutting the outflow valve and bleeding the radiator with the inflow open and it continues to flow with pressure, which it did not do prior to me cleaning it, but I am not sure it is as free flowing as the outflow and definitely not as much as the other towel radiators on the system, you can hear a real rush of water when their valves are adjusted, but the fact that I can bleed it with pressure (with outflow closed) suggests there should be enough flow for hot water to rise through the inflow valve surely, or is there just not enough pressure as this is the tallest radiator on the 1st floor?

When the system was drained I had the radiator off and the inflow and outflow pipe were exposed I did try pour some water into them to see if the water went down the pipes, the outflow took the water away no problems, but the inflow just filled up with water and did not drop at all, is there something on the T junction that only allows water one way into the inflow that possibly explains that??

Thoughts? Any advice appreciated.

Not experienced in plumbing but I feel there is potentially a blockage near the inflow valve, but is it normal for enough water to get through to heat the tail pipe but not the bottom or top or radiator?

Cheers

John

 

[EPH]

What size is the pipe work to the radiators?

 

[Centralheatking]

Hi JPG

Welcome to UKPF

Well your certainly way beyond diy land - and your problem
will get loads of replies on here I hope.

Given that you have carried out a comprehensive set of correct
procedures I would

Find your lowest drain off point (mt cock) and connect a hose pipe
from an outside tap and the MT open the mt and then open the
outside tap - full mains pressure with all the rad valves open might well clear
the block BUT WATCH the gauge on the boiler no more than1.5 bar

CHKing

 

[diamondgas]

Hi John, you have done a lot to try and resolve the issue. My approach would be to turn off both valves, remove the radiator and holding a bucket under each valve individually try and fully open the valve. What you're trying to ascertain is the quantity of flow through each valve. Initially you will get a thin jet, potentially powerful. You really need to know what the flow is fully open. If you can, attach a hose to the valve you're going to open, instead of holding a bucket, and place it in the loo or sink. this'll reduce the potential for damage from dirty water.

Obviously the pressure will quickly drop on the boiler as you let water out!

I hope that makes sense?

 

[stevetheplumber]

stick amains fed hose on to each valve in turn obviously you need an open end some where for it to go prv or drain off

 

[johnpaul.gordon]

Hello,

Firstly thanks for the replies they are all really helpful as this is all new to me.

I think my next step is to suggest what DiamondGas suggests, checking the quantity of flow from each of the valves, I think I know what the answer will be but it would be good to confirm it in any case, I fully expect the flow from the inflow pipe to be less than the outflow.

Question on this though, is it normal for the tail pipe and valve to get really hot even with just a trickle of water getting through, but the radiator not to warm at all?

The next step will be for me to try a mains flush with a hose, I am holding back on this to be honest as I am a little nervous doing it on my own so will wait till the weekend to get some assistance and somebody to watch the pressure. It also gives the Fernox F3 a little longer to do some good on the rest of the system before I flush it.

Many Thanks

John

 

[johnpaul.gordon]

Oh and the pipes are a hybrid of 15mm and microbore(8mm I think) in the house, the pipes into the radiator with the issue are 15mm and look a few years old but I think it is because it is part of a recent extension, the majority of the rest of house is microbore and looks much older.

 

[bewsh]

You could attach remove the radiator, attach a hose to the valve (one at a time), close all other radiators, open the valve to let water flow through the hose, then open the filling loop to blast some mains water through the pipe?

 

[johnpaul.gordon]

That might not be a bad idea before trying a full hose flush, can I ask if there is any risk of opening up the filling loop to run through the blocked valve given that there is a potential blockage? I am thinking if the water cannot get through it will back up, will this be ok as long as the pressure is monitored?

 

[Centralheatking]

This is a good idea - simpler than my proposal CHK

You could attach remove the radiator, attach a hose to the valve (one at a time), close all other radiators, open the valve to let water flow through the hose, then open the filling loop to blast some mains water through the pipe?