Fig. 140.
Fig. 141.
The general rule is to lay the main pipes from the boiler so that the pipe will drain from the boiler. Where this is done it is necessary to have a drip just before the steam enters the circulation. This drip is connected to a trap, or, if the condensed water is returned to the boiler, the drip is arranged accordingly.
But it is the best practice to lay the main pipe with the lowest part at the boiler, so that the drip will take care of itself, and not require an extra trap, nor interfere with the return circulation.
When steam is turned into cold pipes the water of condensation gets cold after running a short distance, and if it has to go through a small drip pipe full of frost it will probably be frozen. Then, unless it is followed up with a pail of hot water, the whole arrangement will be frozen and a great many bursted pipes will result. Whenever turning steam on in a system of very cold pipes, only one room should be taken at a time, and a pail of hot water should be handy so that if the pipe becomes obstructed it can be thawed immediately without damage.
When pipes become extensively frozen there is nothing to do but take them out and put in new ones.
