I've a hot-liquid filled tank (approx. 5000 Litres) at ground level within which there's a considerably good vacuum. Approx. 100 mmHg abs pressure. Is it possible to pump out liquid from this tank using a pump (any kind) without destroying the vacuum in the tank? What kind of pump would work best? Normally to remove liquid I (a ) either destroy the vacuum & then use a regular CFG pump or (b) connect to a second tank maintained at a lower abs pressure (i.e. better vacuum) & let the pressure differential do the sucking A centrifugal pump doesn't work because it cavitates. The hot liq. is only about 10 C under its boiling boint (@100 mmHg) and the NPSH available isn't sufficient. That's my theory. Would a reciprocating pump / dosing pump work better? What other options do I have? I've about 6 ft of total head available from surface of liq. till pump position. The discharge head isn't much. Approx. 10 ft & negligible pressure drop.