Baxi 105e Pressure Sensing Pipes how to seal / leaking

[molegrip]

Hi. Ok, a job i've done a few times before - replacement of the whole Diverter Assembly for the old Baxi 105e. After re-filling, i have no leaks apart from weeping from both the copper Pressure Sensing tubes on the front diaphragm housing. I know the 2 little O-Rings need to be correctly inserted into the holes on the top of the body, and when i took the unit apart to start again, both O-Rings were mashed up from over-tightening trying to stop the leaking. I'd be grateful for any tips or tricks concerning the best way to place these O-Rings in the threaded holes they need to go to the bottom of before screwing the pipes back in. Eg, would you recommend silicone paste on the ring ? (Asking for trouble there! ) Also, should one expect a leak-free fit with only moderate tightening to save the O-Rings from splitting ? Common sense i guess but it helps to know others' opinions. Thanks in advance.

 

[jeff the gasman]

Mole grips are not the answer. I thought they had olives although I may be mistaken. If you’ve mashed them you may need new sensor tubes and olives/O rings. But be gentle.

 

[DP]

Is this 105e or 105 Instant.
105e does not have o rings on the sensing pipes at the Domestivc manifold ( left hand manifold that has I think 6 screws)

If it is the instant, the seals are tiny green washers

 

[molegrip]

Thanks Jeff, not olives but a kind of flared swelling at the end of the pipe ( never a happy thing! ). The bad aspect of this should-be simple job, is that when the diverter body is fixed in the boiler case, it's nigh on impossible to see down the holes where the tiny O-rings go, to check if they are square before pushing down the sensing pipe/s. I even tried the old mirror & torch trick but it didn't work. The inner pipe of the two is really tough to get a good squint at. So although i'd only just fitted the new diverter assembly, i've split the hot water (front) diaphragm container which the sensing pipes go into, from the rest just to hopefully situate new O-rings squarely from the start. Btw, my Baxi 'servicing instructions' booklet doesn't even show the little O-Rings at the ends of the sensing pipes, but they show up on all good exploded diagrams, they are numbered 128 on this - https://www.heatingspareparts.com/image/baxi/htgbqocbaz/110/150512195440499358

 

[ianmcd]

Either I have veen very lucky , or you have been very unlucky, But I used to be an Alpha agent and have removed and re-fitted that diaphragm housing hundreds of time ( same valve for thr Alpha and the Baxi) I have never had one leak ever, think you must be doing something wrong, and have never changed the whole valve either just get the service kit, the rest is just a lump of brass

 

[molegrip]

Thanks Ian, yeah maybe unlucky. When you've done that diaphragm swap all those times, did you take out the sensing pipes ? That's the only place i'm getting the leak. Point taken about the service kit - just thought i'd go the whole hog this time and get the whole 'lump of brass'. Would you mind looking at the exploded diagram i provided the link to above, and say if you think it's wrong, in that it shows O-Rings at the ends of the sensing pipes ? Or do they have olives ? Do you recall either when doing the job ? Thanks. And maybe mine are just welded to the ends of the pipes making a bump / swelling of the pipe-end. When you say i might be doing something wrong, i'm worried that the whole assembly block might not be an exact match for the sensing pipes in my boiler, or alternatively that the ends of the pipes are knackered after 10+ years. If it's the case that they have No O-Rings, or No Olives, is the water-tight seal just a smear-fit metal-on-metal, copper-on-brass ? That woud make the condition of the very ends of the pipes all the more important - i've ordered two new pipes already in case that's it.

 

[CBW]

On Baxi parts arena website, it lists these as the o-rings (numbered 128).

 

[molegrip]

Thanks Chris, i tried the link but it doesn't show any actual location for the O-ring. No picture etc.

 

[CBW]

Thanks Chris, i tried the link but it doesn't show any actual location for the O-ring. No picture etc.

The location is on the diagram that you put up.

 

[molegrip]

I'm totally confused now - i have one bunch of people saying the Baxi 105e sensing pipes never had O-Rings, another on the fence, and exploded diagrams like the one i linked showing O-Rings at the ends of the sensing pipes. Really need the cast-iron fact.

 

[DP]

Might be listed as O ringed but these are olives
the gland will take 10 mm spanner

 

[DP]

replacement of the whole Diverter Assembly for the old Baxi 105e.

Why would you do that.
That item is fully serviceable- never had a need to do that

I think this is a windup
Place O ring in the hole, then expect the sensing tube to seal to it.
This on a Baxi 105e, not the instant that has capnuts and fasit washers to act as seals?

 

[ianmcd]

and say if you think it's wrong, in that it shows O-Rings at the ends of the sensing pipes

It is not O rings, it is olives as you can clearly see in this video, as said I have never had one leak, if you are putting O rings in there that is why it is leaking

 

[molegrip]

THANKS Ian, you're a star. Just before i opened this up i decided to try the old DHW valve (the 6-bolt thing) to see if is a better fit for the sensing pipes than the complete 'new' diverter block i got from ebay, and i connected them without any O Rings. To my relief (so far) they are not leaking! I did smear some fernox joint paste on the threads so that might have helped, anyone's guess. The sensing tubes are so old (10 yrs at least), that what were (as you say) olives, now just look like swellings in the pipe ends, but yep i can see how they used to be olives. I've ordered brand new sensing pipes for any future problems. Many thanks for taking the time. (Looks like Heatingspareparts.com where i got that exploded diagram from, shouldn't be showing 4 O-Rings for the 2 sensing pipes on a Baxi 105e - maybe they are used on some other Baxi's pipes. )