When to change DI resin?

[AZDesertRat]

On any RO/DI you can disconnect the RO from the DI but really a 1/4" tee and 1/4" ball valve are only about $6-$8 at most and maybe a minute to install between the two. Flush kits have nothing to do with it since they are on the waste line.

I think the reason vendors are installing more flush kits is everyone is trying to become more environmentally friendly and reduce their waste. When you reduce the waste the brine or waste becomes more concentrated and may shorten the life of the membrane long term. Flushing could potentially lower that brine TDS but in reality it doesn't do much if anything since the waste line is running any time the membrane is in operation so flusing all he time. You should not even attempt to reduce the waste though if you are not using a water softener of soft water and your TDS is above average no matter how much you flush with a flush kit. Membranes must be flushed, there is no getting around that fact and it is the 3:1 to 4:1 waste ratio that provides that flushing. If you have lower than normal TDS and somewhat soft water you might get by with 3:1 waste ratio. If you have very soft water and very low tap TDS then you may get away with 2:1 waste ratio but that is pretty rare in most of the US with an average TDS of 250 and moderately hard to hard water.

 

[Kaba]

Last November I bought one of the 6 stage 150gpd brs units because it was $100 off. I just changed 1 resin bed, and it honestly wasn't packed very well. I make about 15 gallons a week, and I always flush my ro for a minute. I also have a T before the di, with a ball valve right after the T and right before the di. When I need to make water I open the valve on the T and throw all that water to waste until I see the tds (in line tds meter) get below 5. And it jumps up over 100 on its way down. Once it's below 5 I open the value to the di. There's also a tds meter between the 2 resin beds and at the end. I'll change resin once the middle tds meter reads 1. And I'll just move the second resin bed over and put the new stuff at the end.
Without that bypass when you first start you'll get a lot of junk pushed through your resin beds.