How do I remove hard water stains from my Trex deck??

https://www.trex.com/trex-owners/care-and-cleaning/

Try vinegar and a scrub brush

Wet & Forget is suppose to be a good cleaner for composite decks.

I would ask Trex. Visit their website they may have a faqs page or questions and answers Or maybe a troubleshooterpage. It is likely a common subject that has been asked and answered. If not call their customer service. Hope this helps

Was wondering if you ever found a solution to hard water deposits on your Trex. I have the same issue and have tried a couple of suggestions without success. Frustrated. Not sure if this message will find you.

Give the Trex company a call and ask.

Hi Gerri, hope this helps you out. It's safe to use vinegar for this. The vinegar should be allowed to sit for 15-20 minutes and then rinsed away with non-hard water. If hard water must be used to rinse, dry with a cloth or use a blower to dry surfaces.

https://www.decksdirect.com/knowledge-builders/keep-trex-decking-clean#:~:text=Hard%20water%20can%20leave%20spots,white%20vinegar%20on%20decking%20surfaces.

Spray with white vinegar, let sit, then scrub and rinse. If you have hard water you will need to dry it either by hand or with a dryer - I would use a leaf blower.

Check with the company for the best cleaning method.