When you say you bought your DI for car washing, do you mean for you washing your own car or for a car washing business?
(i’m a bit confused as you say your pressure washer is drawing through the DI but if your a business then surely you go to them and use their mains water...how do you know all their TDS’s)
If for your own car, then the only reason it lasted “years” is because you probably only washed your car twice a year.
If a business then it didn’t last years...it just didn’t.
What size is your DI?
From a 25litre, and 300+ppm, you’ll be very lucky to get 3/4 weeks before the resin needs changing., very lucky.. Thats an input of 370+ and getting 0 out using approx 300litres a day.
That’s how a friend of mine started cleaning windows so thats from real world experience.
So if you’re using a third of that a day for car washing then you’ll be lucky to get 12 weeks.
If you’re a business then I can never understand why people get less than a 450gpd RO even if they dont need it.
It costs a couple of hundred and then your done apart from changing filters every so often which are pennies.
Although from a cost to labour ratio perspective, in the time you’ll take faffing with the RO, producing and transferring the pure and future filter costs...wouldn’t it just take you the same amount of time to just dry the cars?
If you’re just cleaning your own car then I’d just spend the tenner and take it to the local romanians rather than go to this trouble and maybe use the spare time to spend some time with your wife/husband or local brothel....something more worthwhile anyway.
Hope I helped