- Joined
- Jun 22, 2018
- Messages
- 54
- Reaction score
- 56
It's more of an ion issue inside the membrane, @spectrapure can explain it. The way I remember it, when the RO or RODI shuts off the ions that are normally stopped by the membrane can bleed through and upon startup it will be the job of the DI resin to remove it.
Correct.
If you do that multiple times a day, you'll prematurely deplete your DI, but if you can get that down to only a few times a week, then you wont have that TDS creep.
You'll still get TDS creep in the membrane (in fact it'll likely be slightly higher as it will have been sitting for longer), but on your example you'll only have to pay to deal with it once per week rather than multiple times per day. So orders of magnitude saving.
I seek to avoid this entirely by having an equal tee fitting just after the output of my RO membranes (i.e. just before the input to the DI cartridges). On the tee is a ball valve which drains to waste. Each time I start my RO/DO system, I open the ball valve so that the first few litres of output don't go through my resin. That initial high TDS output goes down the drain. Sometimes I'll check the TDS before closing the valve or sometimes I'll just wait a couple of minutes. Personally, I have found this one change saved me the most amount of money on resin. To be honest it's not just the money to me - I cannot stand changing resin so anything that reduces that I'm happy with.