RO/DI water is so pure it is hard to measure individual contaminants with test kits, it requires very expensive lab instruments to do so.

Rely on a good handheld TDS meter or a resistivity meter and that all you need, if it is calibrated and shows 0 TDS or somewhere around 18 megaohms resistivity or very close then you can count on the water being as pure as you need. Test kits do not have the low range accuracy needed to test high purity water and are not accurate.

 

RO/DI water is so pure it is hard to measure individual contaminants with test kits, it requires very expensive lab instruments to do so.

Rely on a good handheld TDS meter or a resistivity meter and that all you need, if it is calibrated and shows 0 TDS or somewhere around 18 megaohms resistivity or very close then you can count on the water being as pure as you need. Test kits do not have the low range accuracy needed to test high purity water and are not accurate.

Thanks AZDesertRat

That's why I was a bit concerned/surprised when my SIO4 test went a lovely shade of green:

SiO_2_Silicic_acid_(mg/l) 1.6-2.0<--This_concerns_me

this is a problem, right?

 

Mix up a batch or new saltwater so the water is stable and not just DI and see how it reads. I'm not convinced the tests on straight DI are valid as DI is very unstable and hard to test with anything besides a TDS meter or resistivity/conductivity meter.

 

for RO/DI you just want to use a TDS and make sure it reads zero. The container you use can leach a little silicate or phosphate into your water. Usually happens with a new container then subsides after a few fillings.

 

Ah - this might be an answer too.

The container is one of these:
http://www.ampulla.co.uk/STACKABLE-...ABLE-CONTAINERS-2.5L---30L/10-Litre-Natural-Stackable-&-Din51-TE-Cap/p-112-452/

http://www.amphorea.co.uk/uploads/10ltr UN Stackable 51mm neck (CH).pdf

 

When testing RO or RO/DI water you should always pull the sample directly from the filter not from a storage container.

 

NEVER, I repeat, NEVER test from a container if you are tesing a RO/DI system. Always test directly from the membrane or DI via a short length of tubing. Exposing RO/DI to atmosphere, containers, scoops, etc. adds additional levels of interference or errors. Make sure you are really testing the source and not something else.