Wow Ali - that is a lot of water!

To get rid of the smell, add a few drops of tea tree or lavender to your wash AND rinse cycles. Also, use NO 'commercial' detergents at all. Get a hold of some Eco Store detergent, or the Eartch Choice works well also. Make sure you only use at most HALF the recommended dose per load.
The smell you are talking about more often comes form the build up of the detergents in the nappies.

Dry your nappies in the sun or at least on an airer as much as possible - not the dryer.

Also, this will allow you to do a single cycle wash - so no need for extra rinses at all - saving you time, money and most importantly, the environment! (No point having a front loader to save water if you use 3 rinse cycles anyway )

HTH