Why is it so hard to find Grade 1 and 2 cylinders?

[Donkmeister]

Some time ago I was on here asking about opinions and experiences of unvented cylinders. Turns out that that option (along with any combi option) would be prohibitively expensive as I have since found out I have an old shared main in 1/2" which would need an expensive upgrade. I've not measured pressure and flow, but as someone on here said, many manufacturers don't recommend installing their products with such an incomer.

So, my only cost-effective/realistic option is for a gravity-fed hot water cylinder. Added bonus is that I should be able to DIY everything except the boiler and primary!

I've noticed that some of the hot water cylinder makers seem to be trying to steer people away from grade 3 copper cylinders due to safety concerns (although they're happy to continue supplying them ). So I've been looking for Grade 1 and 2 cylinders and not had any luck finding anyone who stocks a full range! Even the plumbers merchant here only does grade 3 or unvented.

Do the grade 3 cylinders burst under some fault conditions, or do they corrode out insanely fast? Anyone able to point me at some Grade 1 and/or 2 cylinders?

 

[Slugbabydotcom]

Grade 3 are tested to 10 metres head which is enough for most applications
grade 2 tested to 15 metres
grade 1 tested to 25 metres
These grades are achieved by altering the thickness of the copper
Other details can be found HERE

You may find that anything other than grade 3 could be made to order for all but the most common sizes

 

[swbjackson]

You can also get corrosion resistant cylinders in Grade 3. These are effectively grade 3 cylinders with a grade 2 bottom. Useful in areas where the water is slightly acidic.

There's also no reason why you can't use a stainless steel unvented as a conventional cylinder. Time you figure in the cost of an immersion heater and thermostat the price difference between that and a grade 1 is not a great deal. You can probably flog the controls pack on e-bay as well.

 

[BigBurner]

Stainless cylinders are now competitive to the point few people go for grade 1 & 2 copper. As been mentioned, a cheap stainless unvented cylinder can have the controls stripped away and the potential bomb eliminated. Price up stainless vented cylinders and cheap unvented.

 

[Donkmeister]

Using a stainless cylinder as a simple vented hot water store... I hadn't considered that.

Right, time for me to look at some stainless cylinders.

Thanks guys!

 

[BigBurner]

...

 

[Slugbabydotcom]

some of the hot water cylinder makers seem to be trying to steer people away from grade 3 copper cylinders due to safety concerns

I'd be interested to know more about this. Do you have any links?
I can't understand why yours is such a special case that a normal cylinder like everyone else has won't do. I dont know of anyone who has been killed or maimed by a standard 900 x 450 hot water cylinder or for that matter a standard grade 3 copper cylinder of any size.