Help! Cold water storage tank problem!

[Piglet]

I live in a block of 4 flats, 2 down 2 up. I am on the top floor and am hoping to extend into my attic as my neighbour has done across the hall. Only problem is that there are 2 large, old manky water tanks in my roof space. They are for the 4 flats and as far as i know they are still connected though i am not sure where to. The lids are off both of them and the water inside is not too pleasant.

Is it possible to have these removed and for the 4 flats to be connected only to mains water? Apart from needing them out the way in order to extend into the attic i don't think the ceiling joists are properly supported to hold such a weight safely. Any advice on this situation welcome.

 

[Bahco]

A very good idea to get rid of tanks especially if they are murky as you will all be washing in that water assuming that your drinking water will be off the mains.
Speak to all parties and make sure that these cisterns are not supplying hot water cylinders /CH.
This job may involve putting a stop tap in each flat though and your incoming main will then be shared with all 4 flats