Hi Dudek
A few things to consider.
- your inlet water pressure (do you need a booster pump?)
- your inlet tds
- how many ltrs a day do you need?
- what size of storage tank can you fit in the garage (have you got room for 1000ltr IBC?)
If your water pressure is over 40psi and tds is less than 300 I'd recommend a merlin + 11ltr di vessel into a 1000ltr IBC, the best setup for less than £500 in my opinion.