Motorhome toilets need chemicals to break the waste down into a slurry that's easy to dispose of.

You can buy this chemical for about $50 per four litres, or you can make your own for about a tenth of that price.

Ingredients
250gm powdered Borax
600ml cloudy ammonia
1 bottle MYO (200ml)

Procedure
Use as much hot water as required to dissolve the Borax
Add MYO and ammonia
Add cold water to take the total to five litres

We got this recipe from Adrian & Carrol Capel but ones like it have been around the traps for years.

We use 250ml of this mixture in an 80-litre black water holding tank and it seems to do the job.

For those with a programming bent, maybe the code below will make things clearer.

NOTE: MYO (stands for Make Your Own disinfectant) is a brand of concentrated disinfectant available (as are all the other ingredients) from Woollies and probably all other mayor supermarkets.

function MakeTioletMix () {

   // declare and initialize variables
   //
   m = 200 // amount of MYO
   a = 600 // amount ammonia
   b = "borax"
   t = 5000 // finished quantity
   cw = "cold_water"
   hw = "hot_water"
   bu = "bucket" // must be 5 litres

   bu = bu + b
   bu = bu + hw * 1000 // use about 1000ml to disolve
   do {
      StirMixture()
   } until BoraxDissolved()
   bu = bu + "myo"
   bu = bu + "ammonia"
   var i = t - m - a - 1000 // total - ingredience already added
   for { ; i < t; i++)
      AddColdWater(bu)
      if (BucketIsFull()) break; // catch possible undersized bucket
   }
   return (all_done)
}

function StirMixture() {
   with (large_stick OR serving_spoon) {
      for (i = 0; i < several_times; i++) {
         stir()
      }
   }
}

function AddColdWater (recepticle as bucket) {
   using (tap) {
      recepticle = recepticle + water
   }
}