To produce hot water in the bath are often used bak-register on the tube of the furnace (or boiler in the furnace itself) and external tank in the sink. The circulation of water between them is a natural impulse due to the difference of specific weight of hot and cold fluid in temperature difference.
Due to the small size of the natural pressure in the system (100 – 300 PA), it is recommended to use pipes with an internal diameter of 25 mm and a length not exceeding 2.5 m, and also to observe the slope of the pipe from the remote tank to the tank case. But even with all the above recommendations for installation of pipes it is difficult to provide more than a tenfold time water stays in a remote tank and thus rapid heating of the water in it.
To accelerate heating of the liquid in the remote tank by increasing the frequency of water exchange and to simplify the installation of pipes by reducing the requirements for their length, the diameters and the requirement of compliance with the slope in their laying allows installing the system the circulation pump, which provides artificial circulation of water between the external tank and the tank register.