Shelf Life of test kit reagents

[waterbear]

The FAS titrant is probably the most unstable and should probably be replaced yearly. If it has turned pink it is decidedly bad!
The DPD powder will work even if it is black but if it clumps I would replace it.
I have seen pH reagent (Phenol Red) go bad after a few years. (easy to check if you have the acid and base demand reagents. If they don't cause the color to change the reagent is bad).
If they are kept tightly capped and have not been exposed to temperature extremes the calcium hardness and TA reagents should be fine. I don't really know the shelf life of the CYA reagent but I have gotten exactly the same results from 5 year old reagent and brand new.

Hope this is helpful.

[CarlD]

Well, I DO have a definite rule for when to replace the FAS-DPD powder:

If I open the container and what's inside is moving of it's own accord I:
1) Replace the cap, closing it
2) Get rid of it.