Some of the main mistakes that happen when you hire a carpet cleaning machine usually stems from lack of experience as opposed to machine malfunction. There are mainly two mishaps that can happen which unfortunately can also happen to in-experience professional carpet cleaners. These are:
Over use of the carpet detergents
This happens when there is too much water sprayed into the carpet when cleaning. Ideally steam cleaning would take on average between 4-6hrs to dry depending on ventilation. Should the carpet still be wet after 24hrs this becomes a problem as it then invites the onset of mould and mildew build-up.
The best way to counter this problem is to have the water sucked out and install industrial floor air movers to get the carpets dry as quickly as possible.
Overuse of carpet detergents.
Overusing carpet detergents can at worst damage carpet permanently. The damage results in carpet bleaching, discolouration and damage to the fibers which is irreversible. Once you see too much soap it would be advisable to seek the help of a professional before it's too late.
Most inexperienced individuals will use too much detergent thinking that it will make the carpets cleaner. All hired carpet cleaning machines will generally have a helpline or website help and instructions. However this unfortunately may not be enough as it sometimes comes down to the competency of the individual.
To avoid the worst case scenario where you could be liable to replacing the carpets, this would be the best time to hire a professional carpet cleaning technician. Having better powerful machines this would take a simple rinsing with special acid neutraliser to bring the carpet to a neutral ph.