How Do I Know If A Bucket Is Food Grade?

I have two handy-dandy buckets I use around the house for measuring out gallon-quantities of liquid (as they're graduated on the side). I'm wondering if there is any way to tell if they're food-grade. They say made from HDPE on the bottom, and I believe that's what standard fermenters are made from...

...I ask because I want to use the bucket to combine my mash and sparge volumes for a stove top all grain. Can these HDPE buckets stand up to 150*F + temperatures?

Check this out... I love Google.

CHEC Lists: Plastics: What Do Those Numbers Mean?

I use a hdpe bucket to transfer 185F water from kettle to mashtun, no problems yet.

Yup, HDPE is ok.