What Is The Dosage Of Water For Paediatric TTS?

I am a home care nurse. My pt. just came home from the hospital with a 3.5 Pediatric Bivona TTS flextend cuff trach. We did not have an order for how much water to put in the cuff. There was o.2 mls in the cuff but I am sure some of it evaportated. How much water would you recommend. The pt. is 11 months old