My Montane eVent jacket needed washing and the instructions on the two labels in it were ambiguous, so I contacted Montane and got this reply:
I can confirm that NikWax will not clean this garment, you need to wash it with a liquid detergent before using NikWax to reproof.
I suggest washing a couple of times with biological liquid detergent as you have reproofed over the dirt and grease due to the inaccurate first wash . After you have washed it give it an iron on the face fabric to rejuvenate the DWR.
I spoke to him and he confirmed that it should just be washed in any normal, biological liquid detergent as part of the normal wash – but not detergent powder as this can clog the pores. It can then be washed with Tech Wash to remove the detergent, and reproofed if necessary. But he was adamant that most of the time it should just be chucked in the machine with other laundry.
As someone who hadn’t dared wash it for a year in case it messed up the proffing I still find this hard to believe, but he was very clear about it!