ANSWERS : Workshop

 The existing flooring consists of  concrete slabs 230mm thick sitting on top of concrete beams 450mm thick, and the diameter on the bottom of the funnel is about 4 meters. Thank you for your help :)

Comments

[steveastrouk]

And you want to collect all the water that funnels off the roof onto the slabs ?

Where does the water go now ??

A picture would be worth a thousand words here.

Steve

[matisha23]

It would be collected for use in the building but that's exactly my question, how would the draining system work?
Here is a picture of what the thing would look like.

[steveastrouk]

Tanking an area beneath the stones, so all the water is gathered there is easy. Where are you going to PUT the vast amount of water it will collect ?

[rickharris]

Sounds like a job for an architect. Any opinions give here would be blind to the real situation.

[mole1]

+1 and an engineer? You might consider using the water as a 'gray water' system...non-drinking water for flushing toilets, or landscaping irrigation

[iceng]

Discarded dish washers or washing machines have a bunch of electric water valves you can use to drain your collection of water.

Consider how heavy that funnel will be when filled with H₂O

A