ive had my RO MAN unit for 15 months now
it produces 50 - 60 Gallons a day, 4 days a week
now the guy might be right, mine isnt designed to produce 1000 L's of water, thats why its a 50 or 60 Gall unit
if you get a 100 Gall unit, it will produce 100 Gall's of water (give or take)
keep in mind i use between 100 and 150 L's a day, doing tops only, so the unit produces EXACTLY what i need, i have a 210 L rain water butt in the garage and all is fine and dandy
IF i needed more water, i would get a bigger water storage container (or link TWO rain water butts together ) and leave the RO on for the whole week
in my humble opinion, the RO unit is where people get OVER SOLD the most
as i allways say
Pure water -- Pump -- Pole -- Brush -- glass
it doesnt matter if its DIY built or a 5 K system, it still does the same job