I'm doing two soakaways for rain water; both require 3 cells.

I'm looking at the guidance on paving expert.com.

For 3 cells do I do them as line or can I do a pair and the third one at right angles ?

There is some guidance on the size of the geotextile membrane for me to go on, but how much gravel am I likely to need. I can work out a volume I think from the recommended gravel bed sizes, but what is the volume to weight conversion ?

Many thanks

Rob