How to empty a vented hot water cylinder?

[mike2016]

Hi,

Basic question but how do I safely empty a vented hot water cylinder to allow me to insert a T piece into the main 3/4" outflow pipe at the top of the cylinder? 

I plan to close the feed from the cold water tank and use the hot tap in the bathroom / bath tap to drain off a few litres until the pressure drops. I could drill a small hole in the part of the pipe I'm removing to check and drain off any more using an aluminium foil "gutter" into a bucket just in case. Apart from that are there any other tips anyone has to avoid me flooding the kitchen ceiling below a third time?!!

 

Background:

I'm installing a Mira Mode gravity pumped shower unit so need to tee off the 3/4" to a 1/2" for the hot feed at a 45 degree downward angle to prevent air bubbles entering the pump. 

[PeterW]

Should be a drain in the bottom of the tank, and you’ll need to stop the feed from the tank in the attic first. 

[mike2016]

Ahaa...spotted it - that makes sense!! How troublesome are these after 20-30 years?! 

[ProDave]

You won't need to drain the whole tank for that.

 

And if you REALLY mean a 3/4" pipe I hope you have already sourced the fittings, as 22mm won't fit.

[mike2016]

Phew! Gave me sweats there.....I quoted imperial as I thought they were the same size!! It's all 15/22mm in my hot press though. That matches the solder fittings I've purchased so should be good to go.....

[ProDave]

22 minutes ago, mike2016 said:

Phew! Gave me sweats there.....I quoted imperial as I thought they were the same size!! It's all 15/22mm in my hot press though. That matches the solder fittings I've purchased so should be good to go.....

When I re plumbed my 1930's house 30 years ago, they were all 1/2" and 3/4"  Then you could buy adaptors, both compression and solder to go between imperial and metric.

[dpmiller]

Careful... Imperial is still used in RoI