Baxi Combi Instant 105 HE Leak from behind the Diaphragm?

[Ivor Windybottom]

Hello. I've been doing lots of googling but can't seem to find a similar problem to mine with this boiler.

Firstly (this may or may not be connected), the HW was stick on (the fan was running for ever). The pin that operates the microswitch had got stuck with it out. I gently pushed it in and, after a bit of resistance, it popped back in and for now operates fine. So I'm guessing it got stuck, so probably needs taking apart for a clean-up and some silicone grease.

I can find a diaphragm kit that includes a brass gland and an alu washer. It looks like these are for the front, under the microswitch to me.

The problem I found while looking at all this is that there's a dripping from behind the diaphragm housing. It looks like it's from the join between this unit and the lump behind it, I think where the grub screws hold it in.

Is this something that can be fixed? I'm perfectly happy to take it apart, clean things up and change O rings and washers - if the parts are available.

If new parts are needed then would a new diaphragm housing include a new O ring to seal it into the lump behind?

Apologies for all my terminology no doubt being completely wrong - all help appreciated! Thanks.

 

[Agile]

There is a replaceable "O" ring at the back of the diaphragm unit. Although finding spare ones is not that easy.

But its much more likely to be the large nut with clamping screws part behind which is leaking system water. They can be purchased and fitted although I would class that as four spanners in difficulty.

If it is the "O" ring then turning off mains water and opening a hot tap will stop the leak.

If the big nut then that will cause the system pressure to go down.

Tony

 

[Plumber90]

Looks like another person trying to fix their own boiler that isn't gas safe to me. You should get a competent gas safe engineer in to do any work on the boiler.

 

[Ivor Windybottom]

Thanks very much for your reply, Agile. I'll leave the water off and taps open overnight and see how the tray under the boiler looks. The water looks clear, but the system water is usually pretty clear anyway. It doesn't have that manky smell to it that I know the CH water smells of.

There is a local O-ring specialist that stocks any standard BS-size ones, so I might take a gamble on pulling it apart before seeing if they have one. I was trying to get kitted out before disassembly, as obviously it's very unlikely to go back in without failing badly, so I could be a few days without hot water and heating if I need to order something from further afield.

I understand the difference between electricity, water and gas (and associated vents/chambers etc).

 

[Agile]

What are BS standard sizes?

The one you need is very small !

Tony

 

[Ivor Windybottom]

Well, I found that the drip-drip-drip stopped completely when I pushed the pin (that operates the DHW microswitch) back in. It now only drips while hot water is running. I don't know if this helps to diagnose anything.

I'm going to get a full diaphragm kit and replace it first. I don't expect this to cure the leak (although you never know), but I don't want it sticking on again. I'll make sure everything's clean and shiny inside to prevent sticking again. Then I'll see what happens about the dripping.

I've also found another slower drop at the other side of the boiler. The next time I'm buying a boiler it will be anything-but-a-baxi brand!

Thanks again for your help.

BS O-rings are a full range of sizes, from tiny to huge.

 

[Ivor Windybottom]

Oh, have I just realised what you mean about the O ring being small - is it just a gland around the sliding pin? I was thinking there would be a bigger O ring sealing the join between the two brass lumps. I don't know what's there yet, as I haven't had it apart.

 

[Agile]

It may a gland to you but its also an "O" ring.

About 2mm internal and 6mm external. Only approximate for visualising and not for ordering.

Now where can I see your list of "BS sizes" ?

Tony

 

[Agile]

If it is the "O" ring then turning off mains water and opening a hot tap will stop the leak.

If the big nut then that will cause the system pressure to go down.

Tony

Those are what you should be doing to identify where its leaking from!

Its called diagnosis and in this case non invasive.

You seem to want to be a parts changer!

Tony