Direct combination tank

[Bullbags]

Can someone tell me how direct comination tanks work and why we have them? I've never come accross them before.
I've looked at them in the local mechants and understand you have to fit a float valve and warning pipe to the top chamber. I only need one hot water draw off so I assume I can blank the other three off.
The tank is to provide hot water to a portacabin toilets and 3 washbasins at a bottling plant on a farm. The chap alreday has a combi tank in his current set up but is expanding to move into a bigger barn.
Any experience and knowledge on this matter would be much appreciated.
Cheers

 

[twgas]

you have to fit a float valve and warning pipe to the top chamber.

yes,

taps from one of the top ones, dont forget a drain cock in one of the bottom ones

 

[Bullbags]

Thanks Mick. Any reason why taps from top rather than bottom? even allowing for drain cock.

 

[Bullbags]

If I installed a combi tank do i have to provide any sort of vent pipe back into the tank?