External expansion vessel fitting

dannyjebb · 18 June 2019 at 4:50PM

A few weeks ago we had a boiler service and the gas guy said the expansion vessel had failed and he was amazed we had never had to top up the water all over winter...

The options were £300 for a new internal one inc fitting or £150 for an external one inc fitting.

After looking online it looks like I can fit the external one myself as I am not going anywhere near the gas and don't need to remove the boiler cover.

As the boiler is 10 years old it seems daft to spend 300 on the internal one and I can buy this,

https://www.wolseley.co.uk/product/center-heating-expansion-vessel-18-ltr/

for £25, I have a large length of copper pipe 22mL which will do so I just need to buy a few elbows, a T connector and a connector for the connection to the expansion vessel.

I have checked online and wondered if someone can confirm this is all I need?

[*] Drain the system
[*]T into the boiler return floor pipe which is 22mL
[*]add a few pieces of copper pipe to get to the expansion vessel, only about 2ft away.
[*]charge the expansion vessel to the correct pressure
[*]connect the pipe to the expansion vessel
[*]refil the system (add some inhibitor) checking for leaks...

Is it ok to use 22mL pipe from the return to the EV? all the vids I have seen show using 15mL. don't think this will make a difference but want to check.

Many thanks

southcoastrgi · 18 June 2019 at 6:45PM

What boiler is it ?
What happens to the pressure gauge when you are using it ?
Did he drain the boiler on the service ?

dannyjebb · 18 June 2019 at 8:33PM

Hi,

It's a Vaillant ecotec pro.

When we have the heating on the pressure rises slightly but it has never been low (ie in the zone on the pressure reading) or gone really high.

Not really sure what he did on the service, he showed me the current internal EV and when he pressed the little valve water came out which he said was a sign that the rubber inside had failed and so instead of half the EV being water and half air, it would now be full of water.

Not sure if he drained the boiler though? I wouldn't imagine so unless he could fit all the water in the system in a small washing up basin.

Thanks

Ectophile · 18 June 2019 at 10:34PM

The classic symptoms of a failed expansion vessel are:

When you turn on the heating, the pressure rises up to the maximum, and water drips from the pressure relief valve pipe.
When you turn off the heating, the pressure drops back below normal. Some boilers may refuse to start if this happens, others don't check.

If the pressure is within the normal range, and doesn't go too high or low, then it doesn't look like there's much wrong.

dannyjebb · 19 June 2019 at 7:02AM

I'm stuck on what to do then. Been told by a gas engineer it needs replacing and they advised to turn the Heating on the boiler down to minimum. Obviously this is fine over summer.

Maybe get a second opinion from another company?

Danny

southcoastrgi · 19 June 2019 at 8:25PM

He can't tell if it's faulty or just needs re-pressurising unless he drains the boiler & tries to pump it back up to 0.75 bar, just because he got a little bit of water out of the valve means jack, also just because he is Gas Safe Registered that doesn't mean he knows how to repair boilers, if you aren't having any problems with the pressure as Ecto has mentioned I'd carry on using it as normal & employ a different com for the next service

External expansion vessel fitting

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