[hilland]

if my tap water measures 60 - 80 tdi , can any one with experience tell me what a 450 gpd R O S ystem would take the figures down to, roughly, cheers Ted

[Spruce]

These r/o systems usually work between 97 and 99% efficient provided you have decent water pressure. Mine worked at 98 ~ 99% for a number of years at 60 psi (according to the supplied pressure guage.)

So with a tds of 80 you should expect a water purity to around 1 to 3 ppm which you would polish off with resin.

However, at that tds some won't bother with a resin stage until the membranes start to deteriorate.

[hilland]

thanks , my plan is to put my water through a R O system and then put that through my DI vessel, hoping that it would make my resin last a lot longer, cheers

[Spruce]

thanks , my plan is to put my water through a R O system and then put that through my DI vessel, hoping that it would make my resin last a lot longer, cheers

Obviously there are other considerations to include.

If you are on a water meter then you need to calculate the cost of waste water from the r/o into the equation. My old 450 GPD unit had a 3:1 restrictor so the waste was 3 litres to every 1 litre of pure.
So if you are using 2000 litres of pure water a week, your water bill will be for 8000 litres for the same period. Most have found it cheaper to use resin to bring their tds down from your low level than using an R/O on a meter.