i have a 400ltr tank i have middle of the road pressure fills from empty 4 hours but with the correct microbore hose pump etc youll get alot of windows out of that tank my biggest job is 77 flats ( 300 window app) still have 1/4 tank left over .... 3 bed houses i used to get 25 out of a tank
Thank you for your reply but my question was: How long does it take on average to fill a 500 litre tank? I have a good pressure here.
it depends on what ro you use.
100 gpd about a week

merlin hours and you can fill your swimming pool with the wasted water, or a 4040 anything for 1 and a half to 5 hours, good pressure: there is a massive difference on fill times what do you call good pressure ?
1 bar 2 3 ? each will make a difference.
The fastest is a pumped 4040