Well, finally mastered the in line heater with a cold water start
Get porty out , connect heater, boil kettle, pour into bucket, top up bucket with cold water so its warm and pour into tank, run pump with heater on and solution hose in tank so its recirculating and getting hotter. Vac , pre spray, top up tank then start cleaning. Heater and pipes are nice and hot and well on the go!! Got through a dirty rental property with ease!!