Self contained machines are limited to cleaning low profile carpet, like the style that is glued to the floor.
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Dual, triple, and quad corded machines need multiple electrical circuits to take full advantage of their power.

Self contained extractors need wide open areas to clean.
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High powered extractors clean clean around furniture with ease.

Self contained extractors clean more square feet per hour and use more water per hour.
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High powered extractors are designed to can be outfitted with auto fill and auto dump.

Self contained extractors don't travel up and down a stair case without team lifting.
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High powered extractors can navigate stairs by a single operator.

Self contained extractors are slow going when it comes to upholstery cleaning
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High powered extractors can use internal spray hand tools, bi-directional hand tools.

Self contained extractors can only clean carpet, upholstery, and tile.
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High powered extractors can perform flood extraction, pressure washing, air duct cleaning,..

Some models of self contained extractors can clean carpet bi-directional.
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High powered extractors almost always clean on the 'walk back stroke.'

Self contained extractors are designed for interim or maintenance style cleaning.
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High powered extractors are designed for restorative style cleaning.