Inline TDS meter RO/DI Question

[an411]

I currently have a inline TDS meter on my RO/DI. The TDS meter gives both the in water tds reading and the out TDS reading. I really don't care what the water coming in is. and rather have the TDS meter reading the water coming out the the DI filter rather then before the DI cartridge. Is that fine to Move the TDS meter to after the DI unit. Its conencted with john fittings. The main reason for doing this is so I can see what the TDS reading of the water is after the DI filter cause that is what is going into my tank. That way I know when its not 0 that its time to replace the filters.

[AZDesertRat]

It should be plumbed with the IN probe after the RO membrane but before the DI and the OUT probe after the DI for final RO/DI TDS. Make sure you have the probes oriented in the correct position in the tees.
You do want to know your incoming water TDS too though. This number along with the RO only TDS are how you determine the efficiency of the RO membrane and when it is failing.
That is one of the drawbacks of the inline meters, you only get two dedicated testing points and thats it. They cannot be used portable since they need flow past the probe to work. Thay are also less accurate than a handheld meter since they do not have a temperature probe inside them. They actually measure air temperature and not water temperature and how often are those the same? The error can be quite significant whne air and water are a lot different temperatures like in a heated house in the winter with cold water.
I much prefer a good handheld metere like the HM Digital COM-100, same company but worlds different meter. With a handheld you can measure from whereever you want, the kitchen sink, neighbors, out of your Brute trashcan, the LFS, the grocery store, etc. It is portable and accurate since it does have a temperature probe and calculates correctly.

[an411]

Thanks AZDesertRat I am going to take a look and make sure that it is plumbed correct. Also I will look into one of those handheld TDS meters. SInce the water going into your tank is one of the most important things to check for.

[jlaurence32]

I know two different guys that had the inline TDS meters on their Kent RO units and both read zero when the TDS actually checked around 50 with a real Hanna TDS meter. I wouldn't trust them.