Gurgling sound

[shorner]

I have a BAXI combi boiler which has worked fine for the last year, however, when the boiler first comes on in the morning there is a lot of gurgling up to the water tank. I have bled all of the radiators and the problem still occurs.

This has only happened since I turned the thermostat down so I am guessing it only happens when the pump does not come on. When the thermostat is turned up (so the heating comes on) the problem disappears or is so much less severe that I do not notice it.

Thank you for any advice

 

[oilman]

You say you have a combi boiler, which are mostly fitted to sealed heating systems, so what tank is it that you refer to? Are you sure it's a combi? The boiler should be connected so it comes on only if hot water or heating is required, it should not just start by itself first thing in the morning.

 

[shorner]

My apologies, I may have made some assumptions about my heating system which were incorrect and I should have put a bit more thought into my initial post.

I have BAXI back boiler which heats the water and central heating. The timer is set to turn on both the hot water and central heating at 6:00 in the morning. This is when the gurgling starts, it lasts about 10 minutes. The gurgling has only started since I turned the thermostat down as I did not want the central heating to come on, but still required hot water.

I have a hot water tank in the airing cupboard and two water tanks in the loft. I assumed that the larger of the two water tanks was for the cold water supply and the smaller was related to the central heating.
I am not sure what other information would be helpful but will try to find out info needed.

 

[breezer]

it can not be a combi with tanks that are in use, that was the "error"

 

[shorner]

On further investigation...

It only happens when the pump is off. The boiler starts up and there is a sound of flowing water in the pipe I believe goes up to the hot water tank. It's not until the boiler switches off that the gurgling happens. I am not sure if the air is heading into the hot water tank or the cold water tank?

I'm off to find out what a combi boiler is.

 

[oilman]

it can not be a combi with tanks that are in use, that was the "error"

Sorry breezer, but what point were you making here?


The hot water cylinder circuit may have air in it, is there a bleed point connected to the top of the coil.

 

[breezer]

it can not be a combi with tanks that are in use, that was the "error"

Sorry breezer, but what point were you making here?

I was pointing out that it can not be a combi

 

[AdamW]

I am sure that someone, somewhere in this country has at some time installed a combi to a gravity fed system. Very silly thing to do, but it would work.

Think about it, the mains feeds the cold tank, the cold tank is then feeding down either by virtue of its 20-foot or so head, possibly augmented by a pump. This would give a mains pressure and flow at the combi.

Now, I know that you should never do this, the inlet and outlet of combi boilers should not be pumped, and this would defeat half the object of a combi, but it can be done. However wrong it would be!

Alternatively, it could be a property with relatively low mains pressure, so they have a mains hot and tank cold for the shower. This would improve the flow-rate as the mains pressure would be given over entirely to the hot.

So, 2 reasons why it CAN be a combi with tanks in use.

And now for a hundred reasons why it SHOULDN'T be a combi with tanks in use