Strange TDS readings

[incapearl]

I recently bought an RODI unit used from Craigslist. Came with a TDS meter. The "in" reading is 004 and the "out" reading is 008-010. Are those readings bad/incorrect? Should I replace the batteries or clean the sensors?

 

[m-six hundred]

What brand? Where are the Tds sensors placed?

 

[incapearl]

Here's a couple photos. The left side red is the in and the right side blue is out. Looks like it's just before and after the DI filter.

 

[Nibrown9]

Ian how old are the filters? I'd replace them just to be safe anyways.

 

[briankmarsh1980]

Where are the sensors located? Cant tell from pic but an incoming TDS should be way higher. If you follow the intake line to the first chamber and dont find a sensor. Then its most likely right before the DI and then rights after.... if thats the case your DI is shot. But I cant tell much from your pic

 

[m-six hundred]

I would expect the in reading to be 8-10 and the out should be 0 anything above 0 should be replaced. Contact spectrapure or brs for a replacement.

 

[incapearl]

Thanks for the help guys. I'll replace the membranes to be safe. Or could I just replace the DI to start and see if that helps?

 

[briankmarsh1980]

It depends on where the meter is placed.... I would just replace the DI ...membranes can last a long time

 

[m-six hundred]

I would replace the DI but you should have a good understanding of the route the water is making it through your RO/DI system and where those meters are placed. From the picture I don't understand why the In meter and the Out meter are where they are. You should have the "In" meter after the RO membrane and the "Out" meter after the DI cartridge.

 

[incapearl]

Okay cool. I'll rearrange the placement of the in sensor and replace the DI cartridge and see now that works.

 

[azjohnny]

hand held meters will give you a more accurate reading than the inline , a good one will cost less than $30

 

[Mr. Fancy Pants]

Can you post a better pic of your first (sediment) filter? It looks to me it needs to be replaced ASAP. I have the same RO/DI. If you go to www.airwaterice.com , they have decent pricing on filter replacement packs.

 

[m-six hundred]

Really? Where did you hear that?

 

[Brew132]

I had a handheld and I love the inline so much better (just had it installed). Sometimes dust and whatnot skew the readings in the brute and I find myself washing and rinsing glass cups to make sure that it's the rodi that reads a tds than a contaminate from the cup.

 

[Stolireef]

If I recall the FRAG meeting with the guy from Spectrapure, neither the hand held nor the inline meters are particularly accurate. Rather, they should be used in a comparative way. So, water going into my RO is at 600 tds. Water coming out is at 30 tds. Thus membrane is rejecting about 95% of tds. Calibration is only approximate and you shouldn't assume that your water is actually 0 tds regardless of what your meters say. From what he said, to get to 0 tds, you would need a far more sophisticated setup than any hobbiest would own.

 

[m-six hundred]

Alan your R/O membrane is about due for replacement.

Their manual recommends. "As a general rule; the RO membrane would be considered in good condition when the rejection rate is equal to or greater than 95%"

If you were to buy their 99% rejection membrane you would see 6 tds out and probably extend your Max Cap and DI cartridge by 5 times saving you allot of money.

do you burn through your max cap and di cartridges?

 

[Stolireef]

Alan your R/O membrane is about due for replacement.

Their manual recommends. "As a general rule; the RO membrane would be considered in good condition when the rejection rate is equal to or greater than 95%"

If you were to buy their 99% rejection membrane you would see 6 tds out and probably extend your Max Cap and DI cartridge by 5 times saving you allot of money.

do you burn through your max cap and di cartridges?

I actually spoke with the guys at Spectrapure about this. They told me when the rejection rate goes below about 90% that's when they would recommend changing the membrane. I usually get at least four months (running constant topoff and 20 gallon water changes per week) out of my DI. I have a two stage DI and rotate them (last one becomes third in line and replace the last one) each time a do a change per Spectrapure.

Then again, I just spent the last several months rebuilding my tank because it was doing badly. Maybe I should have changed the membrane sooner. :headwallblue:

 

[m-six hundred]

Strange TDS readings

Eek. I would not run 60 Tds through my max cap. Currently I'm at 8 Tds. My math could be wrong but to me you're going to burn through seven $35 max cap Cartridges in the time I will go through one. Even if my math is bad and you go through three. That's still allot of money.

 

[Stolireef]

Eek. I would not run 60 Tds through my max cap. Currently I'm at 8 Tds. My math could be wrong but to me you're going to burn through seven $35 max cap Cartridges in the time I will go through one. Even if my math is bad and you go through three. That's still allot of money.

So you're getting a year out of the DI cartridges?

 

[Stolireef]

Btw you're probably right about needing to change my membrane. I'm just curious about your experiences.