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DI Resin Life is Short


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So, as the title states, my DI resin is depleting rapidly. This is a new situation since I added the float switch. My best guess is that the float switch is kicking on when I drain a few gallons out of the reservoir, and the initial burst of water coming into the DI resin is a bit higher than the usual.

I'm thinking that I can shut off the RO/DI system and only fill the resivor in batches? I'm thinking shut it off, and when I want to make water, turn it on, purge for 5-10 mintues, then process as normal once the inbound TDS are over the initial spike. Using the float switch as an automatic shut off, not an auto-on when the tank gets low.

Does that make sense? Sound like it will help the DI resin lifespan? Or is there something else going on?

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I'm experiencing the same issue and was also wondering if it was because of the float switch in my reservoir. I leave the water on at night so that it's full in the morning and turn the water off before I leave for work. I'd planned to try to only run it when i need to refill and see if anything changes.

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I have an overall shutoff as well that i use once the float has kicked everything off.

Do you rinse your RO membrane before every batch? Have you measured your TDS coming out of your RO membrane? If you've noticed a pressure drop in the membrane, it may be time to replace if you have decent amounts of TDS bleeding through.

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TDS creep. And your initial guess is correct :)

When your rodi comes on initially, the first bit of water that comes through the membrane and into the resin has quite a high tds. This high tds can shorten di resin lifespan. To avoid TDS creep, only run your system when you need quite a bit of water made. Leaving a system on to kick on and off as the reservoir calls for water during topoffs will quickly deplete di resin.

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  • 3 weeks later...

Small update on my system.

Originally, my line went from the RO membrane to the inbound TDS meter, to the DI Resin, out bound meter, then to the float switch, and finally to the RODI tank.

Now after the inbound TDS I added a Y splitter and the Y goes to two ball valves. One ball valve connects to the old circuit, the other to a waste line to a bucket.

I use the float switch as a auto-shutoff only. Not auto-on, I do manual on now, and my process is:

  • Open waste valve
  • Open the main valve at water supply
  • Let run for 5 minutes or observing the inbound TDS
  • When it gets to about 11 or 12
    • I open the valve to the DI resin
    • Shut the newly added secondary waste valve
  • When float switch cuts off, close all other valves

Monitoring the inbound TDS at startup was showing a huge spike in TDS when the system was firing up. So every time someone got a jug of water, my poor DI resin was hit with a blast of high TDS water. Pretty sure that was chowing through its life span.

Made a couple of hundred gallons with the new setup and it seems to be holding color and outbound is solid at 0. smile.png

Project was easy with the push fittings. Diagram below.


Thanks folks.

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that's one method. the other method is to have a valve/loop that bypasses the flow restrictor. With no flow, water rapidly flows over the RO membrane instead of through it, which removes some of the debris that has settled on the RO membrane.

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