Whats best stuff to use for washing snowboard clothing, it says to not use normal washing powders.

I use Nikwax Techwash to wash it, then every few wash Nikwax TK Wash-In direct to re-proof it. Seems OK.

Email the manufacturer, they should know best

For any technical clothing with a waterproof or water resistant finish, I would use Nikwax Techwash or Graingers Wash in Cleaner. Just make sure your washing machine drawer is clear of built up detergent and conditioner.
If after cleaning, water doesn’t bead up on the fabric like it used to, it would be worth applying a treatment to restore the DWR (durable water repellent) finish again. If your board clothing is insulated, I’d probably go with a spray on treatment like Nikwax TX Direct Spray On otherwise use the TX Wash In.

Thanks, tech wash and tx spray on ordered.

I use Nikwax Techwash to wash it, then every few wash Nikwax TK Wash-In direct to re-proof it. Seems OK.

This. Clean the powder draw and run an empty cycle on 60 degrees first though to get rid of any detergent / softener residue.