As part of the Stuart Turner Techflo pumps you have the QT range and the TP range of single and twin impeller pumps;Single impeller pumps will only allow you to pump either hot or cold water while twin impeller pumps can do both hot and cold and delivers them both at an equal flow.The Stuart Turner Techflo TP pumps have been designed to improve the pressure and flow of the incoming hot and cold water supply. This could be to an individual shower, shower mixer, mixer tap or bath. This type of pump is only suitable for positive head applications.The Techflo QT single impeller pumps are designed to increase water supply delivery to single taps or to pump mixed water from a shower mixer. These are suitable for positive head installations only.