MythBusters and Waterheater.

[stardanny]

I wondering if anyone been watching MythBusters on Discovery Channel about a myth that could a US water heater shoot through a roof when it safety valves and cut off thermstat all failed? Yes, oh s**t. It confirmed.

It very important that all unvented cylinders is to be serviced every year by a competent person.

Dan

 

[kevplumb]

It very important that all unvented cylinders is to be serviced every year by a competent person.

its also important to keep them away from a pair of bearded muppets that just like blowing things up

 

[stardanny]

I agreed.

Is it true that as you live in US, that the drain for PRV and TRV end up where the heater is? Should it go to outside like we do here?

 

[kevplumb]

it should but most of them dont

you can get away with it in the states tho

 

[cowley]

Mid 80's called out to a pub job in south london, when we arrived we found heavy wooden door complete with frame on the pool table, window plus frame complete with burglar bars in car park, roof of gents toilets raised by six inches (back addition flat roof) not one tile left on the wall of a completely tiled gent toilets all caused by a open vented small Sadia electric water heater that someone had decided to connect to a tap, there wasn't anything left of the heater except small pieces of shrapnel all because thermostat failed, we also found they had done the same in the ladies toilets.
Lucky no one was killed and this is true not April fool joke honest.

 

[WDIK]

the truth of the matter is if you take a vessel, plug all its safety devices off then heat it till the contents boil and expand then breach the material of the cylinder then you will have an explosion due the rapid expansion of its content returning to atmospheric pressure.
that carries good for any vessel wether it be a deodorant or an lpg calor gas bottle or a diving cylinder.

fourtunately british standards dont allow this in the home to present as a hazzard.
please read faqs

FAQS

 

[stardanny]

Excellent FAQ.

What it should really is there should be a warning label that the drain pipe for PRV and TRV must not be blocked or cap off, and if it is blocked, then the hot scaling water could back up and out of tundish. I have come across a builder who laid a new patio slabs and I saw the drain pipe outside run down and under paving slabs, I ask where it goes and he said, ran extra pipe to a soakaway full of peashingle. And yes, it come from a unvented cylinder in copper pipe.

Dan.

 

[kevplumb]

and no i didn't do it

 

[stardanny]

I can't see a EV. Is it inside cylinder? Pipes not clipped, no drain to TRV.

 

[kevplumb]

I can't see a EV

normal the regs aint got here yet air bubble internally

 

[Hugh Jaleak]

If anyone is interested, following a previous debate about these "exploding" I emailed the HSE asking for stats. Pasted the reply below:

"Thank you for your enquiry regarding unvented hot water systems. The HSE’s mission statement is 'to ensure that risks to people's health and safety from work activities are properly controlled'. The Health and Safety Executive therefore, is responsible for enforcing health and safety legislation within workplaces and therefore do not hold information on unvented water systems for domestic premises."

They provided a list of other contacts for further information.