RODI water consistently reading 8.3dKH with salifert titration

[dtruitt]

I recently saw a huge alk spike after switching salt mixes. After contacting the manufacturer, I got a reading of 8.3dKH on multiple titrations on "clean" rodi with the salifert kit.

I dont have a TDS meter on hand. I'm assuming the water must not be very clean.

Membrane was changed 6 months ago and has been used for less than 400 gallons. I recently changed out DI resin. I have two mixed beds in series. When the "outer" resin has mostly changed color, I move it to the inner position and reload the new "outer" container.

We have well water. I'm wondering what may be in the water that could show up on these titration tests. Oddly enough, the tank looks better after the WCs with super "high alk" water. If its boron, I may need to start dosing a little boron here and there. If it's truly carbonate / bicarbonate in our water getting through I may have to talk to the landlord.

So before I start buying more test kits, are there molecules other than borate or bicarbonate / carbonate that would manifest as such a high alk reading on a titration? Does the fact that the rodi water comes out of a mixed bed which hasnt changed color yet suggest that on or the other is a better place to start looking?

Should I just get a TDS meter, a boron test kit, and run every test I've got?

 

[jccaclimber]

What does it test at before the RO?

 

[Opus]

According to BRS, that test kit is to only be used on saltwater and will give inaccurate readings on freshwater.

 

[dtruitt]

What does it test at before the RO?

I havent checked that yet. Good idea.

According to BRS, that test kit is to only be used on saltwater and will give inaccurate readings on freshwater.

This is a titration test. Since pure water has no buffering capacity, the color should change instantly on the first drop. I believe I saw Randy discussing how a marine alk titration test should read 0 on rodi, if the test is working correctly and the water is truly pure.

I did buy another, brand new test to confirm these unusual numbers. The new test and the old test (both salifert) match up exactly.

 

[Randy Holmes-Farley]

According to BRS, that test kit is to only be used on saltwater and will give inaccurate readings on freshwater.

I do not believe that is true for an alkalinity titration.

 

[Randy Holmes-Farley]

I recently saw a huge alk spike after switching salt mixes. After contacting the manufacturer, I got a reading of 8.3dKH on multiple titrations on "clean" rodi with the salifert kit.

I dont have a TDS meter on hand. I'm assuming the water must not be very clean.

Membrane was changed 6 months ago and has been used for less than 400 gallons. I recently changed out DI resin. I have two mixed beds in series. When the "outer" resin has mostly changed color, I move it to the inner position and reload the new "outer" container.

We have well water. I'm wondering what may be in the water that could show up on these titration tests. Oddly enough, the tank looks better after the WCs with super "high alk" water. If its boron, I may need to start dosing a little boron here and there. If it's truly carbonate / bicarbonate in our water getting through I may have to talk to the landlord.

So before I start buying more test kits, are there molecules other than borate or bicarbonate / carbonate that would manifest as such a high alk reading on a titration? Does the fact that the rodi water comes out of a mixed bed which hasnt changed color yet suggest that on or the other is a better place to start looking?

Should I just get a TDS meter, a boron test kit, and run every test I've got?

Definitely get a TDS meter.

A depleted DI may release higher alk water than the incoming water.

That said, let's make sure you are using the kit right.

It takes a large portion of a syringe of fluid (the titrant) to cause the color change?

 

[dtruitt]

Definitely get a TDS meter.

A depleted DI may release higher alk water than the incoming water.

That said, let's make sure you are using the kit right.

It takes a large portion of a syringe of fluid (the titrant) to cause the color change?

Correct. It takes about half a syringe full of titrant to achieve a color change. I add drop by drop and swirl between drops.

I'll change out DI resin before running the RODI again.

What would usually accumulate in the water coming out of an RODI with a partially depleted DI cartridge?

 

[Randy Holmes-Farley]

Correct. It takes about half a syringe full of titrant to achieve a color change. I add drop by drop and swirl between drops.

I'll change out DI resin before running the RODI again.

What would usually accumulate in the water coming out of an RODI with a partially depleted DI cartridge?

From well water, there may be a lot of carbonate/bicarbonate stuck to the DI. Then, when the DI is depleted and other salts (such as chloride) come along, the carbonate and bicarbonate can be released. A DI can deplete very fast with high CO2 well water.

 

[dtruitt]

From well water, there may be a lot of carbonate/bicarbonate stuck to the DI. Then, when the DI is depleted and other salts (such as chloride) come along, the carbonate and bicarbonate can be released. A DI can deplete very fast with high CO2 well water.

This makes sense. Lesson learned - buy a TDS meter and use it religiously. Thanks!