The short answer is oxygen bleach works faster with hot water so no. You just use water from your geezer.
Another possibility is Lizol which should work with tap temperature. We don't need to use hot water when cleaning the floor with Lizol so it should work just fine in a top loader. In addition to cutting through grease and grime, Lizol also goes after mould and bacteria so it will also disinfect as well as chlorine bleach without the downsides.
But for a top loader, you will need to use 150ml of Lizol with the machine filled close to the brim. The dosage is one cap which is 15ml for every 4 litres of water. So with 50+ litres in the machine that works out to 150ml of Lizol. Or you can use 200ml. Just make four equally spaced lines along the height of the bottle with a marker so you will know how much to use per go.
If you also have hard water just add 200gm of citric acid to the machine. Lizol and citric acid do not react with each other which means you have now made your own DIY two-in-one cleaner. That descales as well as cleans and disinfects 
Citric acid however works faster at hotter temperatures. So if you have hard water then it's better to go with 50 degree water.
In terms of cost, Lizol works out cheaper than Vanish. With a top loader, because more water is needed you will need to use at least 200gm of Vanish per go with 50+ litres of 50 degree water in the machine.
Whereas with Lizol you will get 5-6 goes for the cost of a 1 litre bottle of Lizol. Vanish in this case is 2-3x more expensive to use for tub cleaning than Lizol.
In a front loader, I use 60 degrees with Lizol because hotter makes for more effective but I think the real value of Lizol is with top loaders which don't have a heater as it is still effective at lower temperatures, unlike Vanish. Given that top loaders never see hot water in operation they likely get more filthy than front loaders so a cleaner/disinfectant like Lizol should help a lot.
Recommended to do a tub clean once every three months. You will need to do two rinses after to wash away the residue. With Lizol pH neutral and dosage of under 1%, any leftover traces in the machine should not affect clothes or skin. Unlike chlorine bleach.
