RODI TDS

[valley]

Hello, my brs 4 stage 75gpd rodi unit started making water that had a tds of 2 ppm last week. I've had the unit for 6 months now and I'm assuming it's time to change out the filters.

I changed the di resin today and it's still producing water with a tds of 1 ppm. I’m pretty sure I packed it in well and there’s no gaps. The original di resin hadn’t really changed color; just a little bit on the bottom had changed to a reddish color. Could it be that I need to change out something else?

 

[Malum Argenteum]

What's the TDS after the RO membrane and before the DI?

 

[valley]

What's the TDS after the RO membrane and before the DI?

The TDS is 1 after the RO and also 1 after the DI. Prior to changing the DI the TDS was 4 after RO and 2 after DI for some reason.

 

[Malum Argenteum]

Given that you're getting the same TDS reading before and after DI resin, it might be that you have RO bypassing the DI resin somehow.

Given a higher RO reading before replacing the resin compared to after replacing the resin, I'd suspect a measurement error (since the DI won't affect the membrane performance).

Is this an inline meter?

 

[EeyoreIsMySpiritAnimal]

Given that you're getting the same TDS reading before and after DI resin, it might be that you have RO bypassing the DI resin somehow.

Or... the meter is off. Hobby grade equipment usually has a decent margin of error.

 

[Malum Argenteum]

Or... the meter is off. Hobby grade equipment usually has a decent margin of error.

I'm sure that's true.

Though, I've had a handful of HM Digital inline meters, and they all read exactly the same when new (I run four channels, and sometimes swap probe positions for troubleshooting purposes) and for a few years of use until the prongs foul, and they all give readings that make sense (expected rejection rate per the membrane and conditions; TDS of zero out of the DI unless it is exhausted).

 

[Uncle99]

Id run a couple of hours through the system first and retest before doing anything.

Mine does that each time I change resin.

 

[valley]

Given that you're getting the same TDS reading before and after DI resin, it might be that you have RO bypassing the DI resin somehow.

Given a higher RO reading before replacing the resin compared to after replacing the resin, I'd suspect a measurement error (since the DI won't affect the membrane performance).

Is this an inline meter?

Yea im using the Hm digital inline meter that came with the unit.

 

[skey44]

Ultimately is there anything wrong with 2 tds… maybe unpopular opinion. Did you watch for a long time? Maybe it takes a while for the tds canister to fully fluidize.