Air getting into CH

[NotSoBigSpenda]

Hi all,

I realise this is probably a very common issue, but I have air getting into my central heating system and am not sure of the reason.

System is open vented. We've had the problem since we moved here 10 years ago. Was collecting in 2 or 3 rads (2 upstairs and 1 downstairs). About 7 years ago we were advised to have a myson aerjec fitted. However, we soon realised that the problem hadn't gone away, although it wasn't as bad and just collecting in 1 or 2 rads.

3 years ago we had a powerflush done, which got a load of crap out (quite impressive I suppose!). At the same time we had a magnet device (forgot name) fitted below the pump. But, still getting build up of air.

2 years ago we had single storey extension. Extra rads were fitted (now 17 in total) which needed pump set to speed 2.

Problem with air persists. Our local plumber had a look at the aerjec arrangement but can't see why this should allow air to be pulled in. His suggestion is to rip out the aerjec and make a combined feed & vent OR to change to a sealed system. But, I'd like to canvas opinion before making a decision.

I've attached pics of the pipework with labels etc. Your recommendations would be welcome!!

 

[John D v2.0]

Small leak on the suction side of the pump? Or air in the system downstream of the pump and a restricted cold feed, but I guess the cold feed has been checked

 

[NotSoBigSpenda]

Small leak on the suction side of the pump? Or air in the system downstream of the pump and a restricted cold feed, but I guess the cold feed has been checked

Thanks for that. I'd thought about restricted cold feed, although that pipework was mostly changed when the aerjec was fitted.

Difficult to know for sure if air getting in downstream, but there are no water leaks and had also been pressure flushed without incident.

One thing I should have mentioned is that there's often a gushing noise when the pump is started and stopped, although not every time. Can then hear air gurgling through and seems to collect in the downstairs cloakroom rad.

 

[John D v2.0]

Thanks for that. I'd thought about restricted cold feed, although that pipework was mostly changed when the aerjec was fitted.

Difficult to know for sure if air getting in downstream, but there are no water leaks and had also been pressure flushed without incident.

One thing I should have mentioned is that there's often a gushing noise when the pump is started and stopped, although not every time. Can then hear air gurgling through and seems to collect in the downstairs cloakroom rad.

You've checked the tank actually has water in it at the bottom? There shouldn't be much in there when cold, but should be some.
Get someone to turn it on and also off while you hold a glass of water over the open end of the vent pipe. Observe what happens.

 

[NotSoBigSpenda]

You've checked the tank actually has water in it at the bottom? There shouldn't be much in there when cold, but should be some.
Get someone to turn it on and also off while you hold a glass of water over the open end of the vent pipe. Observe what happens.

Ok, I've just been and double checked. Definitely water in there, but let us just say I wouldn't be bathing in it! Black as coal. I held a glass of water under the vent pipe and it sucked up about an inch of water on start-up and back out again when the pump stopped. Seems as though blocked feed is probably the reason and tank needs a good clean out too!

 

[DaveHerns]

What is the pipe ending below the surface of the water?

 

[NotSoBigSpenda]

What is the pipe ending below the surface of the water?

That's the overflow.

 

[NotSoBigSpenda]

My plumber/heating engineer just got back to me and said he cleaned out the tank when he did the powerflush, so was shocked to see the current state. He thought maybe that a cleaner had been left in when the extension was built, but it had been drained and then inhibitor added directly to a downstairs rad.

I've got full confidence in my plumber, but just need to seek alternative thoughts and ideas so we can evaluate the best course of action for him to undertake.