Where to dispose of chemistry test by-products?

[gdo]

New to testing my water. Bought a kit from tftestkits.net .
I'm wondering where I should be throwing away the test tube content after each test. Is it safe to throw down the kitchen sink?

Where do you folks dispose of the chemical test by-products?

TIA

 

[Rocket J Squirrel]

Kitchen sink.

 

[JoyfulNoise]

Mud room utility sink with a good rinse of water.

 

[Mdragger88]

I generally test outside on the patio so I fling it in the yard then rinse with spa or pool water & fling that in the yard too. Warning for those doing it inside- the dpd powder will stain light colored countertops/washing machine tops etc. as will the contents from the fc/cc test sample.