In many gardens open-air tanks have been fitted up with hot-water pipes running through them to keep the water sufficiently warm in severe weather.
There are many different systems of heating by hot water circulating in pipes.
They are similar in appearance to a hot-water or steam radiator, and, indeed, some are designed to be filled with water and used as such.
The manner in which the circulation of hot water takes place in the tubes is as follows.
The rate of circulation in the ordinary low pressure hot-water system may be considerably accelerated by means of steam injections.