It is assumed that it is desired to heat by steam to (30° F. five workrooms, each 90ft. by 33ft. by 10 ft. Two 2-in. pipes each side of room would be equivalent to about 200 sup. ft. of heating surface, and this should be satisfactory with steam at low pressure. If the pressure exceeds 101b., less pipe would do, proportionately to the increase in pressure. With five rooms there would be 1,000 sup. ft. of radiation, and with low-pressure steam the supply main from boiler should be 3 in. The return is usually taken in pipe one size smaller, but a 2-iu. pipe should be sufficient in this case. The size of trap cannot be given, but a trap made to work with 1,100ft. to 1,200ft. radiation should be used. The different makers' lists give the sizes. Expansion joints will be required in the 90-ft. runs of pipe.