Air Pocket Keeps Appearing in Towel Rail

[Rob1982]

Hi Guys,

I've got a new boiler and central heating system (about a year old) which may have a problem.

I had to remove the towel rail about 6 months ago to fit a new heating element as the old one had blown. I then did the following as instructed by the plumber:

re fitted the towel rail and filled it back up
filled the system back up to half way on the pressure gauge
bled the towel rail
filled the system back up to half way on the pressure gauge again
turned on the boiler for half an hour and let the system run
turned boiler off
bled the other rads

I then noticed some months later that the towel rail had become cold at the top quarter so i bled it again. Now the towel rail is cold at the top quater again and I know the system pressure goes up and down but its been contently below half way on the gauge for months.

The question is, does it sound like there's a slow leak or is this normal?

I've checked the shops below my flat and there's no sign of water leaking through.

Please let me know what you think.

 

[glasgowgas]

sludge in your system

 

[Rob1982]

can you go into more detail about that? how does sludge cause an air pocket?

Is there anyway of correcting the problem if it is?

 

[MANDATE]

Don't forget that every time you bleed a radiator , the pressure will drop and will need topping up again.

 

[Agile]

Sludge is caused by corrosion of the steel in the rads. A byproduct is gas which you remove by beeding the rads.

Most people do more bleeding than is good for a system. About September/October almost a third of the calls we get are following someone bleeding their rads.

A sealed system normally does not need bleeding!

The installer is meant to have cleaned the systen and added inhibitor.

Tony

 

[fullyuntrainedplumber]

I had a new W/B system boiler installed last September and have had air in my towel radiator ever since although it now appears to be improving, plus
the boiler installer fitted an automatic bleed valve on the system. It never happened with the old gravity fed boiler. The only thing I can think of is that with a pressurised system and the rad being the highest in the house, air naturally will end up at the top of this rad, have not had probs with the other rads. My system was power cleaned by the installer so there is no sludge.
It may just be taking time to settle down.

 

[Rob1982]

The installer is meant to have cleaned the systen and added inhibitor

This was done by the plumber when he finally commissioned the system but it had been filled up for about 4 months without inhibitor.

Would this be enough time to cause this problem due to sludge?


I guess what im getting at is the system leaking or not. From what your saying, air pockets dont occur because of leaks.

I assume i would just get a drop in pressure if this were the case?

 

[Agile]

On a pressurised system the most important thing is to ensure the pressure never goes down near zero.

There are so many of my clients ( mostly female but not all ) who never check the pressure and just call me when the boiler goes off. Now some might see that as a nice little earner but I tell them how to repressurise and do anything I can to avoid having to go out to them.

I am not so concerned about the lack of inhibitor. As long as its kept pressurised there should not be much of a problem if it was clean to start with.

Far worse is those who bleed rads until tnhe pressure is at zero or allow the pressure to fall to zero before repressurising. Doing those things can allow fresh air to enter and react with the iron.

Tony