Abstract: A preheater-potable water condenser for sap concentrating boiler-evaporators. A housing which contains a dual manifolded multitubular heat exchanger is fixed to, but removable from, the vertical vent stack of a hooded syrup concentrator-boiler. The preheater-condenser is an improvement over the state of the art because its vertical positioning, in conjunction with an inclined, ganged and multitubular heat exchanging array, presents a greater heat exchanger surface area to be exposed directly to the boiler exhaust, thus enhancing heat exchange efficiency. In addition to preheating the liquid which is to be concentrated to syrup, positioning above the hood (and away from the boiling and spattering base fluid) facilitates the use of the tubular array as a condenser by which to accumulate distilled water. An oblique (inclined) disposition of the tubular array aids the condensation and accumulation process, the latter being acquired in specially compartmented areas of the housing.