Highrises often have an engineered, redundant array of pumps for boosting domestic water pressure.
Whether a six-story building would call for this would depend on the pressure and volume available from the city. If your building has relatively low pressure from the city, your building may use pumps and tanks. If not, you may just get what you get from the city water pressure.
Your best bet is to ask your building management how domestic water pressure is maintained in your building.
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