I use a DI only set up.
Just wondering if there are there any filters that you can put on before the DI vessels to make the resin last longer that won't slow down tank filling?
I'm reluctant to use a full RO system because I'd like to be able to fill the tank up quickly on site if need be.
Prefilters will slow the flow down slightly when they are new and even more as they become exhausted. Basically, the smaller the micron size on the filter, the slower the flow rate becomes. It is a minimal difference, but a difference none the less.
A carbon filter is a good idea if you own the resin and are regenerating it yourself. Carbon removes the chlorine from the water and the chlorine oxidizes the DI resin. Removing the chlorine from the resin will give the resin a longer life. This means, more regens as opposed to more gallons per regen though.