Boiler - Water flowing through open pipe

Luke2468 · 26 Feb 2017

Hi,

First of all - I'm completely new at this, so please forgive what is probably a very basic question. I've googled without success and would really appreciate some help.

This morning, there was a fast flow of water through a pipe with an open section, next to the boiler. It was loud and initially we were concerned that there was a leak. I turned off the immersion heating switch and after 20 mins or so the water flow stopped.

Does anyone know what this pipe is for, when we should expect to see water flowing through it, and if this indicates a fault with our boiler which will need fixing?

I've attached a couple of photos (hopefully) - one is a close up of the open pipe, and the other shows the whole boiler with the open pipe at the bottom right of the image.

Any advice much appreciated.

Hugh Jaleak · 26 Feb 2017

There is a fault, you will need a Plumber with a "G3" qualification to say he/she is competent to work on an 'Unvented hot water cylinder', which is what you have there. (Its not a boiler.)

oldbuffer · 26 Feb 2017

1. Its not a boiler, its an unvented hot water cylinder.

2. These cylinders should be serviced annually. They contain water at mains pressure, which when heated will be at a higher pressure. If a cylinder fails (almost unheard of), it has the explosive potential of a bomb.

3. Water flows through what is known as a tundish (the black plastic thing with a viewing hole) to relieve excessive pressure and or temperature.

4. Because it is unvented it must only be worked on by someone with what is known as a "G3" qualification.

5. You will need to get an appropriately qualified engineer to diagnose the fault and correct it.

Newboy · 26 Feb 2017

As above - a 'G3' engineer is possibly needed.

Before calling an engineer out, have a read of the users instructions or, if they aren't to hand, try this link and read the section "How do I regenerate the airgap on my Megalfo"
https://www.heatraesadia.com/information/frequently-asked-questions.htm

Or watch the video

https://www.heatraesadia.com/information/how-to-video-guides.htm#tab6572?title=How do I regenerate the airgap on my Megaflo?&ref=&type=form

dilalio · 26 Feb 2017

Yep. As above. Try regeneration of the air bubble/gap first. This is a user procedure that you can do yourself, before having to call in a G3 engineer.
However, even if this cures the fault get your Megaflow booked in for a service, and maybe your boiler at the same time

durhamplumber · 26 Feb 2017

explosive potential of a bomb!!!!..cant beat a bit of scare mongering and worrying ppl..are we talking hand grenade?..cruise missile or full on hydrogen bomb?????

dilalio · 26 Feb 2017

durhamplumber · 26 Feb 2017

oh yes.....hydrogen bomb!

bernardgreen · 27 Feb 2017

Luke2468 said:
I turned off the immersion heating switch and after 20 mins or so the water flow stopped.

A mentioned you need a G3 qualified technician to repair the fault. The flow is from a valve that opens to relieve excessive pressure in the cyclinder or to dump water that has become too hot.

If the water through the open section ( the tundish ) was very hot then the technician needs to check the immersion heater's thermostat and over temperature cut out.
If it was cold water then the technician needs to check the pressure regulator on the cold water supply.

The relief valve(s) needs to be tested and maybe replaced.

durhamplumber said:
oh yes.....hydrogen bomb!

Thermo Oxydihydride bomb to be more precise...

gasbusters · 27 Feb 2017

durhamplumber said:
explosive potential of a bomb!!!!..cant beat a bit of scare mongering and worrying ppl..are we talking hand grenade?..cruise missile or full on hydrogen bomb?????

Its no laughing matter. 3 safety devices are fitted to these and on the very unlikely chance all fail the unvented cylinder has the potential to go off like a bomb and if it does it will likely take out half the house.

Theres a reason why only those with a G3 qual are allowed to work on this.

Agile · 27 Feb 2017

An unvented is meant to be serviced annually!

Sounds as if the OP has never had it serviced!

Hugh Jaleak · 27 Feb 2017

I don't disagree with the information given on unvented cylinders, but if the 3 safety devices on a conventional boiler fail then that has also the potential to go off like a bomb. (It has happened more times than an unvented cylinder failing too!)

If the open vent and cold feed both were to freeze, and the boiler stat fail, then a boiler can continue to heat the water contained within, until in a split second it turns to steam. The water expands to approx 1600 times its original volume as it turns to steam, with the boiler usually giving way, quite catastrophically....

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Boiler - Water flowing through open pipe

Luke2468

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