Expansion vessel position

[Malking]

I see a lot of small 2l expansion vessels fitted horizontally and a few with the water connection at the top, in the legionella advice it mentions having water connections at the base for draining and flushing, also so no debris falls into vessel. From a practical view if the membrane breaks inside then air could escape offering no expansion, I've tried researching, a lot are from Italy but are vague on fitting position, although a couple stated vertical with water conn at base. What do you think?

 

[SimonG]

Where do you see 2 litre vessels fitted? Too small for expansion and too big for water hammer.

 

[Malking]

Where do you see 2 litre vessels fitted? Too small for expansion and too big for water hammer.

On small water heaters, normally fitted on a sink or two that are too far away from calorifiers

 

[Ben-gee]

For use with the 10l or 15l under sink heaters.
I always have the 2l expansion vessel vertical and rigid piped as they usually have no means of being fixed, although I sometimes add strapband if necessary.

I have come across them on long flexies just chucked under the kitchen unit, seems to work ok but not my style.