Sure, you can buy a new refrigerator with a water tap on the door, but - aside from nervousness over the quality of our water - the gadget is more interesting than the beverage and the novelty wears thin. Now beer is another matter. Draught Masters will outfit your old refrigerator with a draft beer tap on the door or install it behind a wall so only the handle shows, in any room that has plumbing. The whole job costs $135 (without the beer, of course), $10 to $15 more if they have to provide ther old refrigerator. Thus, refreshment can be at hand in the laundry room, or a beer rinse can flow right where you shampoo. For short-term refreshment, such as pool and patio parties, Draught Master rents hand pumps ($5), CO: pumps ($10) and red vinyl-covered beer wagons with striped umbrellas which hold half a keg of beer. The wagon rental, including ice and cups, delivered to your door, is $25 ;plus the cost of the beer). And to further set the tone, Draught Master sells beer souvenirs, everything from flashlights to rafts, presumably for when those patio partiesget out of hand.

Draught Masters, 167 Maple Ave. W., Vienna. Open Monday through Friday, 10 a.m. to 9 p.m., Saturday until 6 p.m. 938-6223.