External expansion vessel.

[5544]

Well, I have to go back to a heating job where the boiler expansion vessel needs changing,. For a number of reasons I intend fitting an external one. I am going to put it below the boiler using a half inch to 15mm adaptor, to 15mm then to a flexible hose to connect to the return to the boiler. Can someone remind me of the max length to the expansion vessel using flex. Yes I am gas safe registered, and yes I am self employed, but no one remembers everything. Kindest regards.

 

[Destroyer2813]

Y flexi just hard pipe it and havent most vessels got 3/4 threads on em

 

[5544]

Yes three quarter is right. Thanks

 

[dancinplumba]

Well, I have to go back to a heating job where the boiler expansion vessel needs changing,. For a number of reasons I intend fitting an external one. I am going to put it below the boiler using a half inch to 15mm adaptor, to 15mm then to a flexible hose to connect to the return to the boiler. Can someone remind me of the max length to the expansion vessel using flex. Yes I am gas safe registered, and yes I am self employed, but no one remembers everything. Kindest regards.

Really !! well i never

 

[AWheating]

what has gas safe or being self employed got to do with external expansion vessels?

i would pipe it in copper, chuck the flexi in the van. flexi's and heating temps dont mix well, even on the return.

 

[stoker122]

Hard pipe and make sure the valve can be accessed for charging. We look after several flats in a block, all the expansion vessels are fitted with the valve on the floor.
Only managed to persuade 2 landlords they should be repositioned.

 

[IND_Nick]

Just a quick question on this topic. What is the best practise with the failed internal expansion vessel. If it remains water tight does everyone just leave them be or should it be capped off inside the boiler?

 

[stoker122]

Screw down the dust cap and leave it there.

 

[boza]

dont use a flexy pipe they collapse inside after a short while
and leave the expansion tank in place

 

[MatthewHurt]

This may already be a little bit late - and a possibly misguided piece of advice.. But here goes anyways...

If you are choosing to fit a new/external expansion vessel mainly due to the assumption that the Diaphragm has split and is letting water through to the air side (Meaning the boiler keeps blowing water out of the PRP as soon as it heats up) - HOLD FIRE!

I must have changed about 5 or 6 of them for this reason before someone showed me just how much condensate can collect on the air side of a vessel (approximately half a builders bucket full).

You can make sure this is not the only problem by opening up a drain point (preferably below the boiler) with a hose attached and left hanging into a bucket etc.
Release all the air from the expansion Vessel (by pushing the Schroeder down)
Then attach your foot pump onto the vessel and pump it until water stops coming out.
Then replace the Schroeder valve (if required) and pump the vessel back up to about .8 bar

According to a Vaillant engineer I spoke to about it, expansion vessels almost never split and this (^^^) or a blockage on the pipe leading up to the vessel are the only problems that ever really occur with them.

Hope this helps (even if 5544 has already fitted the external one / if there was another reason for fitting) and I don't mean to teach anyone to suck eggs... It is just a bit of advice I've personally found extremely useful!