i run 4 vans on cold water and all vans worked every possible day they could last year - the only days they didnt work was when the roads were like ice rinks , hot watre or not nobody worked on those days. We lost no days through sub zero temps when the roads were negotiable and with cold yes COLD water.
Easy formula,
oil filled rads in vans at night, go and work during the day the van is warm due to your heater and when really cold keep water running as much as poss as running water doesnt freeze , always keep a bag of rock salt handy.
Job done - no days off, work completed as usual no hassle with gas , boilers , extra expenses , etc
I stopped using oil filler rads in vans as one day when cold I went out and everything inside had frozen (maybe the rad was two small) now use blow heater with cut outs
Poll