I found a bit more information on the National Watermatic Machine, this is from the Feburary 1937 Consumers Digest Magazine. I thought I'd post it in here because it is interesting and good to have in the archives...
<span style="font-family: tahoma,arial,helvetica,sans-serif; font-size: medium;">"The mechanical operation of the National Watermatic differs from the conventional type in that the agitator runs continually in one direction instead of back and forth. This action, together with that of the baffles, causes considerable agitation of the water in the tub, whirling it up around the outside of the tub and down at the center of the tub, somewhat in whirlpool fashion. The dryer of this machine consists of a deep pot or container, lined inside with a heavy rubber sack fastened at the top by means of a substantial clamp ring. A heavy cast aluminum lid with bayonet catches closes the dryer after the wet clothes have been put in place, and is locked by slightly rotating the lid. Water from the mains is then turned into the container under the sack, pushing the sack and its load of wet clothes up against the lid. The pressure of the water applied, often 50 pounds per square inch or more, squeezes the water out of the clothes, water running out from under the edge of the lid onto the drain board, where it can be directed back into the machine or into laundry tubs, as desired. This type of dryer is mechanically well designed, quiet and effective, and requires little or no care in placing wet clothes in the dryer. But it does require, for satisfactory operation, a water pressure of at least 30 pounds per square inch, and it is to be noted that one should satisfy oneself in advance that such pressure is in fact available in one's household at all times of day when the washing machine may be required, since there are often large variations in water pressure from city pump reservoir systems, depending upon the amount of water which is being drawn from the mains. </span>
<span style="font-family: tahoma,arial,helvetica,sans-serif; font-size: medium;">No tests were made to determine maximum safe working pressure, but consultant's opinion is that the machine will be safe for pressures up to 100 pounds per square inch. If at any time, e.g., during a fire or otherwise, water pressure in your district exceeds, or may exceed, 75 pounds per square inch, have machine or your piping equipped with special pressure-limiting valve. </span>
<span style="font-family: tahoma,arial,helvetica,sans-serif; font-size: medium;">The National required tightening of the driving belt twice during the test otherwise it had no mechanical difficulty in completing this test. One interesting finding from this test was that the small washing machines were somewhat costlier to operate than the larger machines, considering the amount of washing handled, and were, furthermore, much less effective in washing ability. They did, however, give appreciably less wear on clothes ; it is to be noted that diminishing wear often, though not always, corresponds to decreased washing ability. Thus it is evident that the use of the small machines should be confined to the washing of delicate, slightly soiled garments, or other extra washing insufficient in quantity to warrant the use of the regular-size machines. The National Watermatic machine used an amount of water approximately 50 per cent greater than required on the average for the other two large machines tested ; a part of the additional water is accounted for by that required in the method of drying used, already described above. Differences in water consumption are, of course, to be taken into consideration by consumers living in regions where water is scarce or expensive. Where water is plentiful or cheap or charged for only at a flat rate, the water consumption will be a matter of minor significance. The total cost of operation given in the first two of the following listings is for a wash of twenty pounds, estimated to be the average family weekly wash, and includes the cost of electricity for operating the motor for a maximum washing period of thirty minutes per load at five cents per kilowatt hour, and the cost of heating the water to 140°F by gas of 540 British thermal units at $1.15 per thousand cubic feet (assuming one tub of water for two loads of clothes). On the other machines or on any machine, the high school or college teacher of physics or engineering in your community, or one of his students, can readily calculate these costs for you at different prices of electricity and gas and for gas of other British thermal units value than the 540 named ( which is typical for manufactured gas). When coal is used, the cost of the hot water will fall to one-half or less of the cost with gas. It will be noted that the major cost for operation is for the hot water supply. The cost of electricity is given in two instances so that the reader may more easily estimate that part of his own operating cost which is due to the cost of fuel consumed in providing the hot water. Nine washing machines were tested. </span>
<span style="font-family: tahoma,arial,helvetica,sans-serif; font-size: medium;">Recommended National Watermatic, Model 100 (National Metal Products Co., Waterloo, Iowa) $99.50. One of two ranking about equal for second place in washing effectiveness. The second easiest on clothes of the 5 large machines tested. Capacity, 5.7 lb of dry clothes, 16.5 gal of water. In addition, the dryer used 3 gal of cold water from the mains to damp-dry one load of clothes. The dryer was found to be one of the most effective and the most convenient of all those tested; as it operated quietly and without vibration, many will prefer it to the spinner type. The machine ranked high in quality of construction and ease of operation. It is equipped with automatic timing device (somewhat inaccurate) which can be set for any length of washing period up to 15 min. Drainage of water from the machine is effectuated by means of an aspirator if it is required to deliver water to sink, otherwise drainage is through a hose onto the floor ; the drain hole, however, is located under the agitator (which is not removable) and becomes filled with lint which was difficult to extricate unless machine was kept running during drainage operation. For a 20-lb wash, cost of electricity 2.2c, total cost 10.3c."</span>
