At the present time there is no unanimity of opinion as to the proper procedure for sizing water heaters for use in apartment buildings. Several methods of estimating the maximum demand are in current use.

The development of a procedure and its use are explained by using data collected in a 95-unit apartment building located near the campus of the University of Illinois. It was realized that information on one apartment building is hardly a sufficient sample on which to establish design criteria for hot water systems, but it is sufficient to demonstrate the applicability of the method of analysis.

The method of analyzing data is somewhat different from that used in other studies and it is the first that has given information that pertains to the design load for tankless heaters. There is evidence that the method employed will apply to apartment buildings in general. However, before this can definitely be established the method of analysis should b'e applied to data collected in other buildings. If it is general in nature, the only statistical information that need be determined is the total quantity of water used per day. This quantity, may be based on water used per occupant, per apartment, or for the building as a whole. Determining the total usage of water is a much simpler experimental procedure than having to determine the distri~ bution of maximum rates of use. Therefore, if this method of analysis is general, further experimental work will be greatly snnplified.