open water tank?

[slipstream 1985]

i have an open cold water tank literally is massive round tub in my loft that supplies my shower and taps etc. My drinking water is separate. Is this normal i mean surely dust or bugs etc could get into it. Is there filters further down the pipe system as standard or is it some sort of outdated set up that needs changed?

[slipstream 1985]

Thanks folks will get it cleaned out and covered.