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Yup, that's what Nikwax say:-
http://www.nikwax.com/en-gb/products/productdetail.php?productid=4
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Regular cleaning will enhance the performance of your gear. With regular cleaning, you should be able to clean your gear 5-6 times with Nikwax Tech Wash before it requires re-waterproofing. When Nikwax Tech Wash® alone does not revitalise the Durable Water Repellency (DWR) of your gear (e.g. water does not bead on the fabric surface) it’s time to re-waterproof using the appropriate Nikwax waterproofer.
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Thanks, I'll start with just getting the wash and then buy reproofer if it needs it.