A strong ammonia smell can either be build up, or sometimes a side effect of teething. If your bub is teething and you are getting this smell try pre-washing or rinsing your nappies on cold first, as this helps stop the urine ?setting? into the nappy with the hot wash. If this doesn't work, then strip wash and then do the cold rinse / pre-wash for the duration of the teething.
To strip wash: Always start with clean nappies. First run a maintenance wash on your machine to clean it too (empty machine, full dose of detergent and the hottest wash you can. Don't forget to clean the detergent drawer out) to make sure there is no build up in pipes / your machine that will affect your strip wash.
Washing-up Liquid Method. Soak your nappies over night in a bath full of water and lots of washing up liquid. If they really smell bad, you have nappy cream build up on them, or you are just a glutton for punishment then next morning you can scrub inserts / nappies with a nailbrush with neat washing-up liquid on it. Drain it all off and then bung in washing machine and keep running rinse cycle until you see no more bubbles from the liquid. Suitable for all types of nappy and good at shifting stains.
White Vinegar method: Soak your nappies overnight in a solution of water and white vinegar (1/8th - ¼ vinegar depending on how bad the nappies are) then drain and do a couple of rinses in the washing machine until vinegar smell is gone. Not suitable for PUL, bamboo or nappies with elastic.
Dishwasher tablet method: Use alongside the white vinegar method. Stick all PUL or elastic containing items in the washing machine with a dishwasher tablet. Run on a 60c wash (so only use on wraps etc that can be washed that hot). Run an extra rinse cycle to ensure all gone. Not sure about suitability for bamboo items so wouldn't risk it with them
Tea tree oil is antibacterial and antiviral, so gets used with nappies a lot. I add a little to my pre-wash and also have a cloth wipe with a few drops on in my nappy bucket. Won't help with the ammonia smell though, just with keeping them bug free. Some babies can be sensitive to it, so if you do use then be careful the first time.