Why are TDS numbers so different after installing new RO tank?

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Cloggy

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Sep 1, 2021
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Location
Oakhurst, CA
Hello!

We had an RO system installed when we had our home built 6 years ago. For the first approx 5 years, the TDS readings range started at 11 and never got above 19-21, as that is when we had the filters changed.

In June 2021, our RO technician said we needed a new tank, and he installed a new stainless steel TANKPRO (same brand as before). After changing all filters (including an arsenic filter) and installing the new tank, the best TDS reading has been 30-31, even after draining and refilling the new tank 4 times after installation and even after 2+ months of use. The technician said that a 30 reading is fine as it's less than 80% of the reading of the tap water (246), but that doesn’t explain the difference in TDS readings.

Questions:
1. Why is there such a discrepancy between the “best”/lowest TDS readings (11 vs 30) of the two tanks, and is this okay?

2. With the new “best” TDS reading being 30, what TDS number should flag us that it's time to change the filters or for service -- perhaps 49?

Water pressure and the membrane are fine.

Thanks!
 
The starting water may have changed ?

Your meter may be bad ? When the last time you calibrated it ?

I clean and calibrate my meter once a month.
 
Twowaxhack said:
The starting water may have changed ?

Your meter may be bad ? When the last time you calibrated it ?

I clean and calibrate my meter once a month.
Click to expand...

No change in the water. It's our neighborhood well water. There is lots of decomposing granite in the area so the water is fairly toxic.

What type of meter are you referring to (that you clean and calibrate once a month)?

We know others whose RO reading has always started at 30 here. We just wonder why our start reading went from 11 to 30. Seems odd.

Thanks.
 
So, "the water is fairly toxic"?

I hope you meant maybe dirty, or something like that. But water that is KNOWN to be toxic shouldn't be fed into any system.
I'd have a pre-filtration test done on the water--a COMPLETE test--before monkeying around with any off the shelf water systems.
Toxic is a pretty broad spectrum word, and you need to know EXACTLY what's in the water--and I mean everything--before you start dealing with it.

I remember reading something about my RO system that said something to the effect of "Do not install on a water system known to be...toxic?"
 
Mitchell-DIY-Guy said:
So, "the water is fairly toxic"?

I hope you meant maybe dirty, or something like that. But water that is KNOWN to be toxic shouldn't be fed into any system.
I'd have a pre-filtration test done on the water--a COMPLETE test--before monkeying around with any off the shelf water systems.
Toxic is a pretty broad spectrum word, and you need to know EXACTLY what's in the water--and I mean everything--before you start dealing with it.

I remember reading something about my RO system that said something to the effect of "Do not install on a water system known to be...toxic?"
Click to expand...

Perhaps "toxic" isn't the right word, but it's the way neighbors describe it. Every month our neighborhood receives a notice advising that our water system "has levels of arsenic, gross alpha and uranium above the drinking water standard" and that "Our water system recently violated a drinking water standard." The County sends a few reps once or twice a year to homeowner meetings. The reps announce that they are going to improve the quality of the water. In order to do this they have to raise our water rates, which they have been doing for a few years but have not done anything to improve the water quality.

In any case, my question was about the discrepancy in TDS readings since installing a new tank.

Thanks.
 
Twowaxhack said:
When is the last time you’ve cleaned and calibrated it ?
Click to expand...
It's a Lxuemlu and apparently can't be calibrated (manufacturer claims it doesn't need it), but it has always given consistent readings for RO water (gradually increasing over the life of the filters, then returning to 11 when new ones were installed) and Brita-filtered water.
 
Cloggy said:
It's a Lxuemlu and apparently can't be calibrated (manufacturer claims it doesn't need it), but it has always given consistent readings for RO water (gradually increasing over the life of the filters, then returning to 11 when new ones were installed) and Brita-filtered water.
Click to expand...

Those meters work until they don’t.

The one I looked up to see that name costs 13.00 on Amazon. I personally wouldn’t trust it.
 
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