Towel rad in bathroom needs bleeding every week

[pilsbury]

got a tall towel rad in the bathroom. Once a week the top rail isn’t as hot as the rest. I bleed a bit of air out and it’s fine. Next week, same thing. The other rads are fine.

I’m making some assumptions..... there is a small leak somewhere in the system. The towel rad being the tallest is the one that traps the air.

As I have no clue where this leak is which I’m assuming is small as I very rarely have to top the combi up via the filling loop, will a good slug of that sealing jollop work? Is it any good?

 

[John D v2.0]

No, is your pump located high in the system and what's the static pressure in your system and how many metres above or below the pump is that.
Or do you have a header tank?
Are there any non return valve in the system or zone valves and trvs? It's possible the pressure Brussel vessel is being isolated from part of the system and cooling and pulling in air. We had this in one place and it was impressive how bad the problem was.

 

[pilsbury]

No, is your pump located high in the system and what's the static pressure in your system and how many metres above or below the pump is that.

It’s a Worcester combo located in the garage. So the pump in the boiler is located at head height. What is static pressure? When the boiler is off there is 1.5bar in the system which can be adjusted by the filling loop?

Or do you have a header tank?

No

Are there any non return valve in the system or zone valves and trvs?

Don’t think there are non return valves or zone valves. But all rads bar the towel rad have trvs

It's possible the pressure Brussel vessel is being isolated from part of the system and cooling and pulling in air. We had this in one place and it was impressive how bad the problem was.

Pressure Brussel vessel? I’ll have to google that. Edit: can’t even find that on google!

 

[Nige F]

A pressure Brussel vessel is used at Christmas to measure the velocity and volume of Brussel sprouts powered farts.

 

[pilsbury]

A pressure Brussel vessel is used at Christmas to measure the velocity and volume of Brussel sprouts powered farts.

That clears matters up. Is that how air is getting into my system?

 

[Nige F]

Your pressure vessel is integral with the combi . I think the Brussel sneaked in via predictive text

 

[pilsbury]

Right. So the original question of is the pressure vessel being isolated, cooling and pulling in air? Don’t know. It’s a new Worcester 38cdi. A year old.

 

[John D v2.0]

No idea where Brussel came from!
Sounds like if it's a Combi it should just be pipework with trvs. And the static pressure sounds ok.
Not sure!

 

[John D v2.0]

Do you have inhibitor in the system? It could be your rad rusting from the inside as that results in hydrogen. You can use a lit match to check if it's flammable

 

[durhamplumber]

You can use a lit match to check if it's flammable

Rofl....everyday is a fekin schoolday

 

[John D v2.0]

Rofl....everyday is a fekin schoolday

This guy seems to agree it's basic school chemistry too!

 

[Hot&Cold]

It’s a new Worcester 38cdi. A year old.

is the complete heating system the same age ?

 

[pilsbury]

Yes, have inhibitor. New boiler, old rads and pipe work. Have a magnaclean on it and when it was serviced for its first year, there was some black muck on it but not too much. I could test the air/gas coming out. I’d collect it in a ballon or something!

But to me, a small leak seems most likely. Don’t know if that leak sealer additive is frowned upon. In my old house I had a similar issue. Bunged some of that sealant in and fixed it a treat.

 

[John D v2.0]

But to me, a small leak seems most likely.

If there was a leak, with 1.5 bar in the system, there's only one way it would leak. Water doesn't flow uphill.
Unless you're having to pressurise it to get it to bleed, it wouldn't leak from atmosphere to the system.

 

[pilsbury]

If there was a leak, with 1.5 bar in the system, there's only one way it would leak. Water doesn't flow uphill.
Unless you're having to pressurise it to get it to bleed, it wouldn't leak from atmosphere to the system.

Good logic. Never has it got near 1 bar so as you say, water could p1ss out but air could not enter.

So, my thoughts are clearly twaddle. But what’s the solution?