Andrew, old Banetanks had a thermostat fitted to stop the water in the tank getting to hot for the pump stator, but as you are not using a bane machine this can be bypassed to get the water even hotter ( although the thermostat might already been removed) it as fitted on the side where the coolant pipes entered the tank. it has a big adjustable nob fitted on it, you can't miss it, if its there.
also if you fit too powerful machine onto the waste tank it will pull soiled water into the vacuum, i removed my Bane machine and fitted a petrol T/M, if the waste tank got more than half full the T/M would suck up soiled water because the tank is very shallow. a normal T/M waste tank is tall and thin this is short & long, this is what causes the problem