I pressure cooked / sterilized my hydroton the other night.
My cooker is a 23 quart and can hold almost a five gal. bucket of rock.
Here is how I just recycled my hydroton. A five gal. bucked filled with semi-cleaned hydroton. I filled with hot water and added a large 3% bottle of H2O2. Mixed well and let soak over night.
Put on a bucket lid with many holes drilled into it, flipped upside down in the bath tub to drain.
I took my cooker and added two inches of water (just like canning) and then dumped in the rock and put on the lid.
I put it on the stove and high heat until it starts to vent (constant steam from the weight spout) after 10 min I put on the weight.
I let it come up to 15 pounds of pressure, adjusting the heat, and cooked it for 30 min under high steam pressure.
You have super heated rock, it will take a long time for pressure to come down to zero. LEAVE THE FUCKER ALONE!
When pressure is down to zero, take the weight off and wait another 15 min before unlocking the cooker.
ITS HOT! Open the lid to shield your face.
I noticed that any roots or other matter is pushed up and will settle on the top of the rocks.
LET COOL and then pick out what your can. What ever bug, virus, or bacteria that may of been on your rocks are DEAD and sterilized.
The rock is HOT, do not dump back into a plastic bucket or expose to cold water until cool. Bucket could melt and the rocks could burst like a hot marble being dripped into water.
When cool, dump back into bucket, put on filter lid and flip to drain remaining water.
Vegetable gardening season just started. I had to use my pressure cooker for something
Also works to sterilize fish tank gravel.