RODI lower tds in than out???

[Zer0.]

Hey all,

As the title says, Im getting less tds in than im getting out.

I have the 4 stage value plus rodi from BRS.

I thought my resign must have been exhausted so i got new resin and same thing. Thought maybe I just got a bad batch of DI reson so ordered second batch but im still having same thing.

I am letting the new DI resin run for at least an hour before taking these reading.

So Im thinking the RO membrane, these things say they should last 3 to 5 years however, and i have had mine two years or slightly less. With what I would think to be moderate use. Use membrane "Flush" after every brute filled up for 5 min or so.

Any thoughts?

Also is 13 or 14 TDS bad for reef? I guess maybe you cant tell cause you don't know what those 13 or 14 solids are, but in general.

Thanks as always,
-Z

[shifty51008]

Change out the carbon and sediment filters every 6 months or when the pressure starts to drop which ever comes first.

To check the membrane take the tds reading of tap water and the tds after the membrane but before the di, this will give you the rejection rate. If that is lower than 94% then i would replace it or you will burn through the di fast.

The di just needs to be changed after tds reads 1ppm.

I cant say if 14ppm is good or bad because you dont know what is in that 14ppm.

Also make sure your getting around 4:1 waste to good water. If not that will clog your membrane faster than normal.

And try to have around 60psi or more.

Hope that helps

[sleepydoc]

Where are you measuring? If your RO water is reading 20, that will burn through the DI resin twice as fast as a TDS of 10, so you can burn through resin pretty quickly if your membrane is shot. I can't see how it would be higher, though.

Like shifty said, start by checking your pressure, then measuring the TDS of your source water, before the RO membrane, after the membrane and after the DI. If your carbon & sediment blocks are old, they should be replaced as well.

[Opus123]

Can you give us the following readings:

TDS of tap water
TDS after RO
TDS after DI

This will help determine where the issue is at. If your DI is brand new then you should be getting 0 tds after you run a few gallons thru it.

[baitrunner]

any chance you may have changed the flow? reason i ask is i had an old unit that hadn't been used for years (4 stage). I had to replace one cylinder that was cracked, new membrane and all new filters. When installing the new membrane i reversed order when reconnecting the hoses - needless to say i burned up my my resin in no time flat! Testing showed the same results you're having (effluent TDS higher than tap water). I swapped the hoses, new resin and bingo - 0 TDS!

[Zer0.]

Hey all,

Thanks for the responses. I'm at work at the moment and cant grab the exact readings at the moment.

The BRS 4 stage plus has the 2 inline tds meters, so one measure after carbon and one after everything (I believe)

Think my numbers are about 14 TDS IN and about 20 out . Not sure how I would get the TDS of my tap water with out buying an external TDS meter.

I beleive I have changed my sediment and carbon about every 6 months, maybe more like every 8 months.

I have always gotten right about 50 psi.

Thanks,
-Z

[Opus123]

Inline aren't the best but they will do. You should unplug one of the meters, probably the one at the end would be easiest. Take the hose feeding the first canister and plug it into the tds meter and get a reading for the tap. Plug it back in and then unplug the tube going from the RO membrane to the DI cartridge and plug it into the tds meter to get the value before the DI. This will tell us if the RO membrane is working.

[ca1ore]

Is this a new system, or recently reconfigured? Ideally, TDS post the RO membrane should be about 5% of raw; with 0 TDS post the DI stage (presuming the resin is not exhausted). If output higher than the input, then perhaps something is incorrectly configured (i.e. maybe measuring the waste by accident).