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I don’t disagree, there are rumours suggesting that the reason British Gas started doing it in the 00’s was simply because it was cheaper, as they used less copper pipe!! :)

Correct, that’s what I was thinking, thanks to your help! I assume I could also use the designs in figure 4 of the guide… and just cap off the cold feed inlet. I just picked figure 5 because it already had the cold feed capped off.

We are getting a bit off track here. But I can assure you my system is perfectly normal! The reason it’s somewhat rare is because it’s only suitable with boilers that have overheat protection built in (like the Suprima). There are multiple threads on this very website about it. Usually from...

This is my current aerjec. The pipe you see leading out the top of it is the combined feed and vent. This is the pipe that goes into the bottom of the F&E tank. There is no other vent pipe or indeed any pipe that goes into the loft, except the cold main, to refill the tank.

Yeah, I don’t have that.

I assumed as it was a separate pipe, it could just be disregarded, as it doesn’t exist on my system!?

The cold feed will be the vent pipe! Combined feed and vent. If it makes it easier to understand… my F&E tank doesn’t have a vent pipe over the top of it. There’s nothing there. It simply vents through the 22mm feed pipe. More info here...

It’s 22mm throughout but does manifold off into microbore. All the rads are microbore. The heating is pumped with an F&E tank. Thanks to John, I am fairly confident that the aerjec is the cause of the problem. It’s definitely piped incorrectly for a combined feed and vent. The boiler flow is...

Yeah had a few comments about it in the past. It’s only possible with 22mm pipe.

2. 1 is too slow for the boiler, and I’m concerned about using speed 3 on the old pipework.

No, it’s a combined feed and vent.

Sadly not Andy, can’t see any anywhere. The only option to bleed the system is at the rads… which are all bled!

Thanks for all your help! I think the confusion is, this combined feed and vent is a concept British Gas started doing about 20 years ago. It’s created by having a 22mm pipe from the bottom of the F&E tank, allowing for the same pipe to feed the system and also vent any air out. It has its...

Looking at the instructions you sent, I think it should have been plumbed like no. 5 instead. Do you agree?

Do you mean from the F&E tank? It’s a combined feed and vent so there isn’t one. The vent is also the feed. The only other cold feed is on the domestic side.

No it isn’t plumbed like that at all. But maybe because there’s no cold feed in situ? The boiler flow simply splits and goes into both inlets, then comes out of the other side on the outlet as a single pipe. It vents up as normal. There’s a picture of it attached. The side you can see is the...

Just to add, I’ve checked the air jack with a fridge magnet this morning (strong enough?!) and it didn’t stick to anything! Hi John, thanks for your help; the boiler flow pipe comes up into the airing cupboard from the floor and splits into the “air jack” in my picture, then goes back down...

Thank you, appreciate your response. I had read elsewhere that this may be the issue. But I was a bit skeptical as the hot water does seem to still vent into the loft pipes as the pipes do get a little warm up there. Could there still be a blockage if this happens?

Hi all I have a standard Y plan heating system with a Potterton Suprima 50 in the kitchen, 3-port valve, Myson Compact CP53 pump, and hot water tank in the airing cupboard, then an F&E tank in the loft; with a combined feed and vent. The heating system is simple and generally performs well...